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Spaceman (Hardwell song)
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"Spaceman"
Single by Hardwell
Released
23 January 2012
Format
Digital download
Genre
Big room house
Length
6:19 (original mix)
Label
Revealed
Producer(s)
Hardwell
Hardwell singles chronology
"Cobra"
(2011) "Spaceman"
(2012) "Call Me a Spaceman"
(2012)
"Cobra"
(2011) "Spaceman"
(2012) "Call Me a Spaceman"
(2012)
"Call Me a Spaceman"
Single by Hardwell featuring Mitch Crown
Released
May 18, 2012
Format
Digital download
Genre
Progressive house
Length
3:09 (radio edit)
Label
Revealed
Songwriter(s)
Robbert van de Corput
Mitch Kroon
Producer(s)
Hardwell
Hardwell singles chronology
"Spaceman"
(2012) "Call Me a Spaceman"
(2012) "How We Do"
(2012)
"Spaceman"
(2012) "Call Me a Spaceman"
(2012) "How We Do"
(2012)
"Spaceman" is a single by Dutch DJ and record producer Hardwell. It was released for digital download on January 23, 2012.[1] A second version called "Call Me a Spaceman" featuring vocals by Dutch singer Mitch Crown and was released in May 18, 2012.[2] Another vocal version was created in collaboration with Bright Lights. Despite Hardwell claiming that the latter was his favorite, his management decided to rather release "Call Me a Spaceman".[3] Titled as "Mr. Spaceman" Bright Lights offered the track as a free download in late 2015. For "Spaceman"'s five-years anniversary he released the remastered Bright Lights version as "Mr. Spaceman (2017 Edit)".[4]
Contents
1 Music video
2 Track listing
3 Charts
3.1 Weekly charts
4 Certifications
5 References
Music video[edit]
On May 18, 2012 Hardwell uploaded the music video for "Call Me A Spaceman" on his YouTube account.[5]
Track listing[edit]
Download digital[6]
Spaceman — 6:19
Download digital[7]
Call Me a Spaceman (Radio edit) (featuring Mitch Crown) — 3:09
Call Me a Spaceman (Extended Mix) (featuring Mitch Crown) — 6:19
Download digital (Carnage Festival Trap Remix)[8]
Spaceman (Carnage Festival Trap Remix) — 3:54
Download digital — EP[9]
Spaceman (Original Mix) — 6:19
Spaceman (Headhunterz Remix) — 5:42
Spaceman (Drown the Fish Remix) — 4:24
Spaceman (Naffz Remix) — 4:35
Call Me a Spaceman (Radio Edit) (featuring Mitch Crown) — 3:09
Call Me a Spaceman (Extended Mix) (featuring Mitch Crown) — 6:19
Download digital (Outer Space Remixes) — EP[10]
Spaceman (Headhunterz Remix) — 5:42
Spaceman (Drown The Fish Remix) — 4:24
Spaceman (Naffz Remix) — 4:35
Charts[edit]
Weekly charts[edit]
Chart (2012)
Peak
position
Belgium (Ultratop 50 Flanders)[11]
5
Belgium (Ultratop 50 Wallonia)[12]
14
Netherlands (Dutch Top 40)[13]
34
France (SNEP)[14]
79
US Hot Dance/Electronic Songs (Billboard)[15]
19
Certifications[edit]
Region
Certification
Certified units/Sales
United States (RIAA)[16]
Gold 500,000
*sales figures based on certification alone
^shipments figures based on certification alone
sales+streaming figures based on certification alone
References[edit]
Jump up ^ "Spaceman (Original Mix) - Beatport". Beatport. Retrieved August 26, 2016.
Jump up ^ "Call Me A Spaceman - Beatport". Beatport. Retrieved August 26, 2016.
Jump up ^ Wild, Maximilian: "Doch noch veröffentlicht! Hardwell feat. Bright Lights - Mr. Spaceman (Free Download)" in (German). Dance-Charts. Retrieved March 11, 2017.
Jump up ^ Meadow, Matthew: Hardwell Releases 2017 of “Spaceman” For Free For 48 Hours. YourEDM. Retrieved March 11, 2017
Jump up ^ "Hardwell ft. Mitch Crown - Call Me A Spaceman (OFFICIAL MUSIC VIDEO)". YouTube. May 18, 2012. Retrieved August 26, 2016.
Jump up ^ "Spaceman - Single". iTunes Store. Apple Inc. Retrieved August 26, 2016.
Jump up ^ "Call Me a Spaceman (feat. Mitch Crown) - Single". iTunes Store. Apple Inc. Retrieved August 26, 2016.
Jump up ^ "Spaceman (Carnage Festival Trap Remix) - Single". iTunes Store. Apple Inc. Retrieved August 26, 2016.
Jump up ^ "Spaceman - EP". iTunes Store. Apple Inc. Retrieved August 26, 2016.
Jump up ^ "Spaceman (Outer Space Remixes) - EP". iTunes Store. Apple Inc. Retrieved August 26, 2016.
Jump up ^ "Ultratop.be – Hardwell – Spaceman" (in Dutch). Ultratop 50. Retrieved August 26, 2016.
Jump up ^ "Ultratop.be – Hardwell – Spaceman" (in French). Ultratop 50. Retrieved August 26, 2016.
Jump up ^ "Nederlandse Top 40 – Hardwell feat. Mitch Crown" (in Dutch). Dutch Top 40. Retrieved August 26, 2016.
Jump up ^ "Lescharts.com – Hardwell – Spaceman" (in French). Les classement single. Retrieved August 26, 2016.
Jump up ^ "Hardwell Chart History (Hot Dance/Electronic Songs)". Billboard. Retrieved August 26, 2016.
Jump up ^ "American single certifications – Hardwell". Recording Industry Association of America. If necessary, click Advanced, then click Format, then select Single, then click SEARCH
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Hardwell
Discography
Studio albums
United We Are (2015)
Extended plays
Hardwell & Friends Vol. 1 (2017)
Hardwell & Friends Vol. 2 (2017)
Singles
"Zero 76"
"Spaceman"
"Call Me a Spaceman"
"Apollo"
"Jumper"
"Countdown"
"Dare You"
"Everybody Is in the Place"
"Arcadia"
"Young Again"
"Don't Stop the Madness"
"Eclipse"
"Sally"
"Echo"
"Follow Me"
"Off the Hook"
"Mad World"
"Live the Night"
"No Holding Back"
"Thinking About You"
"Creatures of the Night"
Related articles
Revealed Recordings
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Speed of sound
From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
For other uses, see Speed of sound (disambiguation).
Sound measurements
Characteristic
Symbols
Sound pressure
p, SPL,LPA
Particle velocity
v, SVL
Particle displacement
δ
Sound intensity
I, SIL
Sound power
P, SWL, LWA
Sound energy
W
Sound energy density
w
Sound exposure
E, SEL
Acoustic impedance
Z
Speed of sound
c
Audio frequency
AF
Transmission loss
TL
v
t
e
The speed of sound is the distance travelled per unit time by a sound wave as it propagates through an elastic medium. In dry air at 0 °C (32 °F), the speed of sound is 331.2 metres per second (1,087 ft/s; 1,192 km/h; 741 mph; 644 kn). At 20 °C (68 °F), the speed of sound is 343 metres per second (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or a kilometre in 2.91 s or a mile in 4.69 s.
The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior.
In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: sound travels most slowly in gases; it travels faster in liquids; and faster still in solids. For example, (as noted above), sound travels at 343 m/s in air; it travels at 1,484 m/s in water (4.3 times as fast as in air); and at 5,120 m/s in iron (about 15 times as fast as in air). In an exceptionally stiff material such as diamond, sound travels at 12,000 metres per second (26,843 mph);[1] (about 35 times as fast as in air) which is around the maximum speed that sound will travel under normal conditions.
Sound waves in solids are composed of compression waves (just as in gases and liquids), and a different type of sound wave called a shear wave, which occurs only in solids. Shear waves in solids usually travel at different speeds, as exhibited in seismology. The speed of compression waves in solids is determined by the medium's compressibility, shear modulus and density. The speed of shear waves is determined only by the solid material's shear modulus and density.
In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure for the speed of an object moving through the medium. The ratio of the speed of an object to the speed of sound in the fluid is called the object's Mach number. Objects moving at speeds greater than Mach1 are said to be traveling at supersonic speeds.
Contents
1 History
2 Basic concepts
2.1 Compression and shear waves
3 Equations
4 Dependence on the properties of the medium
5 Altitude variation and implications for atmospheric acoustics
6 Practical formula for dry air
7 Details
7.1 Speed of sound in ideal gases and air
7.2 Effects due to wind shear
7.3 Tables
8 Effect of frequency and gas composition
8.1 General physical considerations
8.2 Practical application to air
9 Mach number
10 Experimental methods
10.1 Single-shot timing methods
10.2 Other methods
10.3 High-precision measurements in air
11 Non-gaseous media
11.1 Speed of sound in solids
11.1.1 Three-dimensional solids
11.1.2 One-dimensional solids
11.2 Speed of sound in liquids
11.2.1 Water
11.2.2 Seawater
11.3 Speed of sound in plasma
12 Gradients
13 See also
14 References
15 External links
History[edit]
Sir Isaac Newton computed the speed of sound in air as 979 feet per second (298 m/s), which is too low by about 15%,[2]. Newton's analysis was good save for neglecting the (then unknown) effect of rapidly-fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiabatic process, not an isothermal process). This error was later rectified by Laplace.[3]
During the 17th century, there were several attempts to measure the speed of sound accurately, including attempts by Marin Mersenne in 1630 (1,380 Parisian feet per second), Pierre Gassendi in 1635 (1,473 Parisian feet per second) and Robert Boyle (1,125 Parisian feet per second).[4]
In 1709, the Reverend William Derham, Rector of Upminster, published a more accurate measure of the speed of sound, at 1,072 Parisian feet per second.[4] Derham used a telescope from the tower of the church of St Laurence, Upminster to observe the flash of a distant shotgun being fired, and then measured the time until he heard the gunshot with a half second pendulum. Measurements were made of gunshots from a number of local landmarks, including North Ockendon church. The distance was known by triangulation, and thus the speed that the sound had travelled was calculated.[5]
Basic concepts[edit]
The transmission of sound can be illustrated by using a model consisting of an array of spherical objects interconnected by springs.
In real material terms, the spheres represent the material's molecules and the springs represent the bonds between them. Sound passes through the system by compressing and expanding the springs, transmitting the acoustic energy to neighboring spheres. This helps transmit the energy in-turn to the neighboring sphere's springs (bonds), and so on.
The speed of sound through the model depends on the stiffness/rigidity of the springs, and the mass of the spheres. As long as the spacing of the spheres remains constant, stiffer springs/bonds transmit energy quicker, while larger spheres transmit the energy slower.
In a real material, the stiffness of the springs is known as the "elastic modulus", and the mass corresponds to the material density. Given that all other things being equal (ceteris paribus), sound will travel slower in spongy materials, and faster in stiffer ones. Effects like dispersion and reflection can also be understood using this model.[citation needed]
For instance, sound will travel 1.59 times faster in nickel than in bronze, due to the greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen (protium) gas than in heavy hydrogen (deuterium) gas, since deuterium has similar properties but twice the density. At the same time, "compression-type" sound will travel faster in solids than in liquids, and faster in liquids than in gases, because the solids are more difficult to compress than liquids, while liquids in turn are more difficult to compress than gases.
Some textbooks mistakenly state that the speed of sound increases with increasing density. This is usually illustrated by presenting data for three materials, such as air, water and steel, which also have vastly different levels compressibilities which more than make up for the density differences. An illustrative example of the two effects is that sound travels only 4.3 times faster in water than air, despite enormous differences in compressibility of the two media. The reason is that the larger density of water, which works to slow sound in water relative to air, nearly makes up for the compressibility differences in the two media.
A practical example can be observed in Edinburgh, when the "One o' Clock Gun" is fired at the eastern end of Edinburgh Castle. Standing at the base of the western end of the Castle Rock, the sound of the Gun can be heard through the rock, slightly before it arrives by the air route, partly delayed by the slightly longer route. It is particularly effective if a multi-gun salute such as for "The Queen's Birthday" is being fired.
Compression and shear waves[edit]
Pressure-pulse or compression-type wave (longitudinal wave) confined to a plane. This is the only type of sound wave that travels in fluids (gases and liquids). A pressure-type wave may also travel in solids, along with other types of waves (transverse waves, see below)
Transverse wave affecting atoms initially confined to a plane. This additional type of sound wave (additional type of elastic wave) travels only in solids, for it requires a sideways shearing motion which is supported by the presence of elasticity in the solid. The sideways shearing motion may take place in any direction which is at right-angle to the direction of wave-travel (only one shear direction is shown here, at right angles to the plane). Furthermore, the right-angle shear direction may change over time and distance, resulting in different types of polarization of shear-waves
In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression waves are supported in gases and liquids. An additional type of wave, the transverse wave, also called a shear wave, occurs only in solids because only solids support elastic deformations. It is due to elastic deformation of the medium perpendicular to the direction of wave travel; the direction of shear-deformation is called the "polarization" of this type of wave. In general, transverse waves occur as a pair of orthogonal polarizations.
These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake, where sharp compression waves arrive first, and rocking transverse waves seconds later.
The speed of a compression wave in fluid is determined by the medium's compressibility and density. In solids, the compression waves are analogous to those in fluids, depending on compressibility and density, but with the additional factor of shear modulus which affects compression waves due to off-axis elastic energies which are able to influence effective tension and relaxation in a compression. The speed of shear waves, which can occur only in solids, is determined simply by the solid material's shear modulus and density.
Equations[edit]
The speed of sound in mathematical notation is conventionally represented by c, from the Latin celeritas meaning "velocity".
For fluids in general, the speed of sound c is given by the Newton–Laplace equation:
c = K s ρ , {\displaystyle c={\sqrt {\frac {K_{s}}{\rho }}},}
where
Ks is a coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases);
ρ is the density.
Thus the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material, and decreases with increase in density. For ideal gases the bulk modulus K is simply the gas pressure multiplied by the dimensionless adiabatic index, which is about 1.4 for air under normal conditions of pressure and temperature.
For general equations of state, if classical mechanics is used, the speed of sound c is given by
c = ( ∂ p ∂ ρ ) s , {\displaystyle c={\sqrt {\left({\frac {\partial p}{\partial \rho }}\right)_{s}}},}
where
p is the pressure;
ρ is the density and the derivative is taken isentropically, that is, at constant entropy s.
If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations.
In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO2 which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies (> 28 kHz).[6]
In a dispersive medium, the speed of sound is a function of sound frequency, through the dispersion relation. Each frequency component propagates at its own speed, called the phase velocity, while the energy of the disturbance propagates at the group velocity. The same phenomenon occurs with light waves; see optical dispersion for a description.
Dependence on the properties of the medium[edit]
The speed of sound is variable and depends on the properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with the addition of a dependence on compressibility.
In fluids, only the medium's compressibility and density are the important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrated in the hot chocolate effect.
In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to the temperature and molecular weight, thus making only the completely independent properties of temperature and molecular structure important (heat capacity ratio may be determined by temperature and molecular structure, but simple molecular weight is not sufficient to determine it).
In low molecular weight gases such as helium, sound propagates faster as compared to heavier gases such as xenon. For monatomic gases, the speed of sound is about 75% of the mean speed that the atoms move in that gas.
For a given ideal gas the molecular composition is fixed, and thus the speed of sound depends only on its temperature. At a constant temperature, the gas pressure has no effect on the speed of sound, since the density will increase, and since pressure and density (also proportional to pressure) have equal but opposite effects on the speed of sound, and the two contributions cancel out exactly. In a similar way, compression waves in solids depend both on compressibility and density—just as in liquids—but in gases the density contributes to the compressibility in such a way that some part of each attribute factors out, leaving only a dependence on temperature, molecular weight, and heat capacity ratio which can be independently derived from temperature and molecular composition (see derivations below). Thus, for a single given gas (assuming the molecular weight does not change) and over a small temperature range (for which the heat capacity is relatively constant), the speed of sound becomes dependent on only the temperature of the gas.
In non-ideal gas behavior regimen, for which the van der Waals gas equation would be used, the proportionality is not exact, and there is a slight dependence of sound velocity on the gas pressure.
Humidity has a small but measurable effect on the speed of sound (causing it to increase by about 0.1%–0.6%), because oxygen and nitrogen molecules of the air are replaced by lighter molecules of water. This is a simple mixing effect.
Altitude variation and implications for atmospheric acoustics[edit]
Density and pressure decrease smoothly with altitude, but temperature (red) does not. The speed of sound (blue) depends only on the complicated temperature variation at altitude and can be calculated from it, since isolated density and pressure effects on the speed of sound cancel each other. Speed of sound increases with height in two regions of the stratosphere and thermosphere, due to heating effects in these regions.
In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see Details below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature.
Since temperature (and thus the speed of sound) decreases with increasing altitude up to 11 km, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source.[7] The decrease of the speed of sound with height is referred to as a negative sound speed gradient.
However, there are variations in this trend above 11 km. In particular, in the stratosphere above about 20 km, the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer. This produces a positive speed of sound gradient in this region. Still another region of positive gradient occurs at very high altitudes, in the aptly-named thermosphere above 90 km.
Practical formula for dry air[edit]
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Approximation of the speed of sound in dry air based on the heat capacity ratio (in green) against the truncated Taylor expansion (in red).
The approximate speed of sound in dry (0% humidity) air, in meters per second, at temperatures near 0 °C, can be calculated from
c a i r = ( 331.3 + 0.606 ⋅ ϑ ) m / s , {\displaystyle c_{\mathrm {air} }=(331.3+0.606\cdot \vartheta )~~~\mathrm {m/s} ,}
where ϑ {\displaystyle \vartheta } is the temperature in degrees Celsius (°C).
This equation is derived from the first two terms of the Taylor expansion of the following more accurate equation:
c a i r = 331.3 1 + ϑ 273.15 m / s . {\displaystyle c_{\mathrm {air} }=331.3~{\sqrt {1+{\frac {\vartheta }{273.15}}}}~~~~\mathrm {m/s} .}
Dividing the first part, and multiplying the second part, on the right hand side, by √273.15 gives the exactly equivalent form
c a i r = 20.05 ϑ + 273.15 m / s . {\displaystyle c_{\mathrm {air} }=20.05~{\sqrt {\vartheta +273.15}}~~~~\mathrm {m/s} .}
which can also be written as
c a i r = 20.05 T / K m / s {\displaystyle c_{\mathrm {air} }=20.05~{\sqrt {T/K}}~~~~\mathrm {m/s} }
where T denotes the thermodynamic temperature.
The value of 331.3 m/s, which represents the speed at 0 °C (or 273.15 K), is based on theoretical (and some measured) values of the heat capacity ratio, γ, as well as on the fact that at 1 atm real air is very well described by the ideal gas approximation. Commonly found values for the speed of sound at 0 °C may vary from 331.2 to 331.6 due to the assumptions made when it is calculated. If ideal gas γ is assumed to be 7/5 = 1.4 exactly, the 0 °C speed is calculated (see section below) to be 331.3 m/s, the coefficient used above.
This equation is correct to a much wider temperature range, but still depends on the approximation of heat capacity ratio being independent of temperature, and for this reason will fail, particularly at higher temperatures. It gives good predictions in relatively dry, cold, low pressure conditions, such as the Earth's stratosphere. The equation fails at extremely low pressures and short wavelengths, due to dependence on the assumption that the wavelength of the sound in the gas is much longer than the average mean free path between gas molecule collisions. A derivation of these equations will be given in the following section.
A graph comparing results of the two equations is at right, using the slightly different value of 331.5 m/s for the speed of sound at 0 °C.
Details[edit]
Speed of sound in ideal gases and air[edit]
For an ideal gas, K (the bulk modulus in equations above, equivalent to C, the coefficient of stiffness in solids) is given by
K = γ ⋅ p , {\displaystyle K=\gamma \cdot p,}
thus, from the Newton–Laplace equation above, the speed of sound in an ideal gas is given by
c = γ ⋅ p ρ , {\displaystyle c={\sqrt {\gamma \cdot {p \over \rho }}},}
where
γ is the adiabatic index also known as the isentropic expansion factor. It is the ratio of specific heats of a gas at a constant-pressure to a gas at a constant-volume( C p / C v {\displaystyle C_{p}/C_{v}} ), and arises because a classical sound wave induces an adiabatic compression, in which the heat of the compression does not have enough time to escape the pressure pulse, and thus contributes to the pressure induced by the compression;
p is the pressure;
ρ is the density.
Using the ideal gas law to replace p with nRT/V, and replacing ρ with nM/V, the equation for an ideal gas becomes
c i d e a l = γ ⋅ p ρ = γ ⋅ R ⋅ T M = γ ⋅ k ⋅ T m , {\displaystyle c_{\mathrm {ideal} }={\sqrt {\gamma \cdot {p \over \rho }}}={\sqrt {\gamma \cdot R\cdot T \over M}}={\sqrt {\gamma \cdot k\cdot T \over m}},}
where
cideal is the speed of sound in an ideal gas;
R (approximately 8.314,5 J · mol−1 · K−1) is the molar gas constant(universal gas constant);[8]
k is the Boltzmann constant;
γ (gamma) is the adiabatic index. At room temperature, where thermal energy is fully partitioned into rotation (rotations are fully excited) but quantum effects prevent excitation of vibrational modes, the value is 7/5 = 1.400 for diatomic molecules, according to kinetic theory. Gamma is actually experimentally measured over a range from 1.399,1 to 1.403 at 0 °C, for air. Gamma is exactly 5/3 = 1.6667 for monatomic gases such as noble gases;
T is the absolute temperature;
M is the molar mass of the gas. The mean molar mass for dry air is about 0.028,964,5 kg/mol;[citation needed]
n is the number of moles;
m is the mass of a single molecule.
This equation applies only when the sound wave is a small perturbation on the ambient condition, and the certain other noted conditions are fulfilled, as noted below. Calculated values for cair have been found to vary slightly from experimentally determined values.[9]
Newton famously considered the speed of sound before most of the development of thermodynamics and so incorrectly used isothermal calculations instead of adiabatic. His result was missing the factor of γ but was otherwise correct.
Numerical substitution of the above values gives the ideal gas approximation of sound velocity for gases, which is accurate at relatively low gas pressures and densities (for air, this includes standard Earth sea-level conditions). Also, for diatomic gases the use of γ = 1.4000 requires that the gas exists in a temperature range high enough that rotational heat capacity is fully excited (i.e., molecular rotation is fully used as a heat energy "partition" or reservoir); but at the same time the temperature must be low enough that molecular vibrational modes contribute no heat capacity (i.e., insignificant heat goes into vibration, as all vibrational quantum modes above the minimum-energy-mode, have energies too high to be populated by a significant number of molecules at this temperature). For air, these conditions are fulfilled at room temperature, and also temperatures considerably below room temperature (see tables below). See the section on gases in specific heat capacity for a more complete discussion of this phenomenon.
For air, we introduce the shorthand
R ∗ = R / M a i r . {\displaystyle R_{*}=R/M_{\mathrm {air} }.}
In addition, we switch to the Celsius temperature ϑ {\displaystyle \vartheta } = T − 273.15, which is useful to calculate air speed in the region near 0°C (about 273 kelvin). Then, for dry air,
c i d e a l = γ ⋅ R ∗ ⋅ T = γ ⋅ R ∗ ⋅ ( ϑ + 273.15 ) , {\displaystyle c_{\mathrm {ideal} }={\sqrt {\gamma \cdot R_{*}\cdot T}}={\sqrt {\gamma \cdot R_{*}\cdot (\vartheta +273.15)}},}
c i d e a l = γ ⋅ R ∗ ⋅ 273.15 ⋅ 1 + ϑ 273.15 , {\displaystyle c_{\mathrm {ideal} }={\sqrt {\gamma \cdot R_{*}\cdot 273.15}}\cdot {\sqrt {1+{\frac {\vartheta }{273.15}}}},}
where ϑ {\displaystyle \vartheta } (theta) is the temperature in degrees Celsius(°C).
Substituting numerical values
R = 8.314 510 J / ( m o l ⋅ K ) {\displaystyle R=8.314\,510~\mathrm {J/(mol\cdot K)} }
for the molar gas constant in J/mole/Kelvin, and
M a i r = 0.028 964 5 k g / m o l {\displaystyle M_{\mathrm {air} }=0.028\,964\,5~\mathrm {kg/mol} }
for the mean molar mass of air, in kg; and using the ideal diatomic gas value of γ = 1.4000, we have
c a i r = 331.3 1 + ϑ 273.15 m / s . {\displaystyle c_{\mathrm {air} }=331.3~~{\sqrt {1+{\frac {\vartheta }{273.15}}}}~~~\mathrm {m/s} .}
Finally, Taylor expansion of the remaining square root in ϑ {\displaystyle \vartheta } yields
c a i r = 331.3 ( 1 + ϑ 2 ⋅ 273.15 ) m / s , {\displaystyle c_{\mathrm {air} }=331.3~(1+{\frac {\vartheta }{2\cdot 273.15}})~~~\mathrm {m/s} ,}
c a i r = ( 331.3 + 0.606 ⋅ ϑ ) m / s . {\displaystyle c_{\mathrm {air} }=(331.3+0.606\cdot \vartheta )~~~\mathrm {m/s} .}
The above derivation includes the first two equations given in the "Practical formula for dry air" section above.
Effects due to wind shear[edit]
The speed of sound varies with temperature. Since temperature and sound velocity normally decrease with increasing altitude, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source.[7] Wind shear of 4 m/(s · km) can produce refraction equal to a typical temperature lapse rate of 7.5 °C/km.[10] Higher values of wind gradient will refract sound downward toward the surface in the downwind direction,[11] eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind. This downwind refraction effect occurs because there is a wind gradient; the sound is not being carried along by the wind.[12]
For sound propagation, the exponential variation of wind speed with height can be defined as follows:[13]
U ( h ) = U ( 0 ) h ζ , {\displaystyle U(h)=U(0)h^{\zeta },}
d U d H ( h ) = ζ U ( h ) h , {\displaystyle {\frac {\mathrm {d} U}{\mathrm {d} H}}(h)=\zeta {\frac {U(h)}{h}},}
where
U(h) is the speed of the wind at height h;
ζ is the exponential coefficient based on ground surface roughness, typically between 0.08 and 0.52;
dU/dH(h) is the expected wind gradient at height h.
In the 1862 American Civil War Battle of Iuka, an acoustic shadow, believed to have been enhanced by a northeast wind, kept two divisions of Union soldiers out of the battle,[14] because they could not hear the sounds of battle only 10 km (six miles) downwind.[15]
Tables[edit]
In the standard atmosphere:
T0 is 273.15 K (= 0 °C = 32 °F), giving a theoretical value of 331.3 m/s (= 1086.9 ft/s = 1193 km/h = 741.1 mph = 644.0 kn). Values ranging from 331.3 to 331.6 m/s may be found in reference literature, however;
T20 is 293.15 K (= 20 °C = 68 °F), giving a value of 343.2 m/s (= 1126.0 ft/s = 1236 km/h = 767.8 mph = 667.2 kn);
T25 is 298.15 K (= 25 °C = 77 °F), giving a value of 346.1 m/s (= 1135.6 ft/s = 1246 km/h = 774.3 mph = 672.8 kn).
In fact, assuming an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the speed of sound using the standard atmosphere—actual conditions may vary.
Effect of temperature on properties of air
Temperature
T (°C)
Speed of sound
c (m/s)
Density of air
ρ (kg/m3)
Characteristic specific acoustic impedance
z0 (Pa·s/m)
35 351.88 1.1455 403.2
30 349.02 1.1644 406.5
25 346.13 1.1839 409.4
20 343.21 1.2041 413.3
15 340.27 1.2250 416.9
10 337.31 1.2466 420.5
5 334.32 1.2690 424.3
0 331.30 1.2922 428.0
−5 328.25 1.3163 432.1
−10 325.18 1.3413 436.1
−15 322.07 1.3673 440.3
−20 318.94 1.3943 444.6
−25 315.77 1.4224 449.1
Given normal atmospheric conditions, the temperature, and thus speed of sound, varies with altitude:
Altitude Temperature m/s km/h mph kn
Sea level 15 °C (59 °F) 340 1,225 761 661
11,000 m−20,000 m
(Cruising altitude of commercial jets,
and first supersonic flight) −57 °C (−70 °F) 295 1,062 660 573
29,000 m (Flight of X-43A) −48 °C (−53 °F) 301 1,083 673 585
Effect of frequency and gas composition[edit]
General physical considerations[edit]
The medium in which a sound wave is travelling does not always respond adiabatically, and as a result the speed of sound can vary with frequency.[16]
The limitations of the concept of speed of sound due to extreme attenuation are also of concern. The attenuation which exists at sea level for high frequencies applies to successively lower frequencies as atmospheric pressure decreases, or as the mean free path increases. For this reason, the concept of speed of sound (except for frequencies approaching zero) progressively loses its range of applicability at high altitudes.[9] The standard equations for the speed of sound apply with reasonable accuracy only to situations in which the wavelength of the soundwave is considerably longer than the mean free path of molecules in a gas.
The molecular composition of the gas contributes both as the mass (M) of the molecules, and their heat capacities, and so both have an influence on speed of sound. In general, at the same molecular mass, monatomic gases have slightly higher speed of sound (over 9% higher) because they have a higher γ (5/3 = 1.66…) than diatomics do (7/5 = 1.4). Thus, at the same molecular mass, the speed of sound of a monatomic gas goes up by a factor of
c g a s , m o n a t o m i c c g a s , d i a t o m i c = 5 / 3 7 / 5 = 25 21 = 1.091 … {\displaystyle {c_{\mathrm {gas,monatomic} } \over c_{\mathrm {gas,diatomic} }}={\sqrt {{5/3} \over {7/5}}}={\sqrt {25 \over 21}}=1.091\ldots }
This gives the 9% difference, and would be a typical ratio for speeds of sound at room temperature in helium vs. deuterium, each with a molecular weight of 4. Sound travels faster in helium than deuterium because adiabatic compression heats helium more, since the helium molecules can store heat energy from compression only in translation, but not rotation. Thus helium molecules (monatomic molecules) travel faster in a sound wave and transmit sound faster. (Sound travels at about 70% of the mean molecular speed in gases; the figure is 75% in monatomic gases and 68% in diatomic gases).
Note that in this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas gives the gas additional ways to store heat which do not affect temperature, and thus do not affect molecular velocity and sound velocity. Thus, the effect of higher temperatures and vibrational heat capacity acts to increase the difference between the speed of sound in monatomic vs. polyatomic molecules, with the speed remaining greater in monatomics.
Practical application to air[edit]
By far the most important factor influencing the speed of sound in air is temperature. The speed is proportional to the square root of the absolute temperature, giving an increase of about 0.6 m/s per degree Celsius. For this reason, the pitch of a musical wind instrument increases as its temperature increases.
The speed of sound is raised by humidity but decreased by carbon dioxide. The difference between 0% and 100% humidity is about 1.5 m/s at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature. The carbon dioxide content of air is not fixed, due to both carbon pollution and human breath (e.g., in the air blown through wind instruments).
The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about 0.1 m/s as the frequency rises from 10 Hz to 100 Hz. For audible frequencies above 100 Hz it is relatively constant. Standard values of the speed of sound are quoted in the limit of low frequencies, where the wavelength is large compared to the mean free path.[17]
Mach number[edit]
Main article: Mach number
U.S. Navy F/A-18 traveling near the speed of sound. The white halo consists of condensed water droplets formed by the sudden drop in air pressure behind the shock cone around the aircraft (see Prandtl-Glauert singularity).[18]
Mach number, a useful quantity in aerodynamics, is the ratio of air speed to the local speed of sound. At altitude, for reasons explained, Mach number is a function of temperature. Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. The assumption is that a particular pressure represents a particular altitude and, therefore, a standard temperature. Aircraft flight instruments need to operate this way because the stagnation pressure sensed by a Pitot tube is dependent on altitude as well as speed.
Experimental methods[edit]
A range of different methods exist for the measurement of sound in air.
The earliest reasonably accurate estimate of the speed of sound in air was made by William Derham, and acknowledged by Isaac Newton. Derham had a telescope at the top of the tower of the Church of St Laurence in Upminster, England. On a calm day, a synchronized pocket watch would be given to an assistant who would fire a shotgun at a pre-determined time from a conspicuous point some miles away, across the countryside. This could be confirmed by telescope. He then measured the interval between seeing gunsmoke and arrival of the sound using a half-second pendulum. The distance from where the gun was fired was found by triangulation, and simple division (distance/time) provided velocity. Lastly, by making many observations, using a range of different distances, the inaccuracy of the half-second pendulum could be averaged out, giving his final estimate of the speed of sound. Modern stopwatches enable this method to be used today over distances as short as 200–400 meters, and not needing something as loud as a shotgun.
Single-shot timing methods[edit]
The simplest concept is the measurement made using two microphones and a fast recording device such as a digital storage scope. This method uses the following idea.
If a sound source and two microphones are arranged in a straight line, with the sound source at one end, then the following can be measured:
The distance between the microphones (x), called microphone basis.
The time of arrival between the signals (delay) reaching the different microphones (t).
Then v = x/t.
Other methods[edit]
In these methods the time measurement has been replaced by a measurement of the inverse of time (frequency).
Kundt's tube is an example of an experiment which can be used to measure the speed of sound in a small volume. It has the advantage of being able to measure the speed of sound in any gas. This method uses a powder to make the nodes and antinodes visible to the human eye. This is an example of a compact experimental setup.
A tuning fork can be held near the mouth of a long pipe which is dipping into a barrel of water. In this system it is the case that the pipe can be brought to resonance if the length of the air column in the pipe is equal to (1 + 2n)λ/4 where n is an integer. As the antinodal point for the pipe at the open end is slightly outside the mouth of the pipe it is best to find two or more points of resonance and then measure half a wavelength between these.
Here it is the case that v = fλ.
High-precision measurements in air[edit]
The effect from impurities can be significant when making high-precision measurements. Chemical desiccants can be used to dry the air, but will in turn contaminate the sample. The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high-precision measurements are performed with air free of carbon dioxide rather than with natural air. A 2002 review[19] found that a 1963 measurement by Smith and Harlow using a cylindrical resonator gave "the most probable value of the standard speed of sound to date." The experiment was done with air from which the carbon dioxide had been removed, but the result was then corrected for this effect so as to be applicable to real air. The experiments were done at 30 °C but corrected for temperature in order to report them at 0 °C. The result was 331.45 ± 0.01 m/s for dry air at STP, for frequencies from 93 Hz to 1,500 Hz.
Non-gaseous media[edit]
Speed of sound in solids[edit]
Three-dimensional solids[edit]
In a solid, there is a non-zero stiffness both for volumetric deformations and shear deformations. Hence, it is possible to generate sound waves with different velocities dependent on the deformation mode. Sound waves generating volumetric deformations (compression) and shear deformations (shearing) are called pressure waves (longitudinal waves) and shear waves (transverse waves), respectively. In earthquakes, the corresponding seismic waves are called P-waves (primary waves) and S-waves (secondary waves), respectively. The sound velocities of these two types of waves propagating in a homogeneous 3-dimensional solid are respectively given by[20]
c s o l i d , p = K + 4 3 G ρ = E ( 1 − ν ) ρ ( 1 + ν ) ( 1 − 2 ν ) , {\displaystyle c_{\mathrm {solid,p} }={\sqrt {\frac {K+{\frac {4}{3}}G}{\rho }}}={\sqrt {\frac {E(1-\nu )}{\rho (1+\nu )(1-2\nu )}}},}
c s o l i d , s = G ρ , {\displaystyle c_{\mathrm {solid,s} }={\sqrt {\frac {G}{\rho }}},}
where
K is the bulk modulus of the elastic materials;
G is the shear modulus of the elastic materials;
E is the Young's modulus;
ρ is the density;
ν is Poisson's ratio.
The last quantity is not an independent one, as E = 3K(1 − 2ν). Note that the speed of pressure waves depends both on the pressure and shear resistance properties of the material, while the speed of shear waves depends on the shear properties only.
Typically, pressure waves travel faster in materials than do shear waves, and in earthquakes this is the reason that the onset of an earthquake is often preceded by a quick upward-downward shock, before arrival of waves that produce a side-to-side motion. For example, for a typical steel alloy, K = 170 GPa, G = 80 GPa and ρ = 7,700 kg/m3, yielding a compressional speed csolid,p of 6,000 m/s.[20] This is in reasonable agreement with csolid,p measured experimentally at 5,930 m/s for a (possibly different) type of steel.[21] The shear speed csolid,s is estimated at 3,200 m/s using the same numbers.
One-dimensional solids[edit]
The speed of sound for pressure waves in stiff materials such as metals is sometimes given for "long rods" of the material in question, in which the speed is easier to measure. In rods where their diameter is shorter than a wavelength, the speed of pure pressure waves may be simplified and is given by:
c s o l i d = E ρ , {\displaystyle c_{\mathrm {solid} }={\sqrt {\frac {E}{\rho }}},}
where E is Young's modulus. This is similar to the expression for shear waves, save that Young's modulus replaces the shear modulus. This speed of sound for pressure waves in long rods will always be slightly less than the same speed in homogeneous 3-dimensional solids, and the ratio of the speeds in the two different types of objects depends on Poisson's ratio for the material.
Speed of sound in liquids[edit]
Speed of sound in water vs temperature.
In a fluid the only non-zero stiffness is to volumetric deformation (a fluid does not sustain shear forces).
Hence the speed of sound in a fluid is given by
c f l u i d = K ρ , {\displaystyle c_{\mathrm {fluid} }={\sqrt {\frac {K}{\rho }}},}
where K is the bulk modulus of the fluid.
Water[edit]
In fresh water, sound travels at about 1481 m/s at 20 °C (see the External Links section below for online calculators).[22] Applications of underwater sound can be found in sonar, acoustic communication and acoustical oceanography.
Seawater[edit]
See also: Sound speed profile
Speed of sound as a function of depth at a position north of Hawaii in the Pacific Ocean derived from the 2005 World Ocean Atlas. The SOFAR channel is centred on the minimum in the speed of sound at ca. 750-m depth.
In salt water that is free of air bubbles or suspended sediment, sound travels at about 1500 m/s (1500.235 m/s at 1000 kilopascals, 10 °C and 3% salinity by one method).[23] The speed of sound in seawater depends on pressure (hence depth), temperature (a change of 1 °C ~ 4 m/s), and salinity (a change of 1‰ ~ 1 m/s), and empirical equations have been derived to accurately calculate the speed of sound from these variables.[24][25] Other factors affecting the speed of sound are minor. Since in most ocean regions temperature decreases with depth, the profile of the speed of sound with depth decreases to a minimum at a depth of several hundred meters. Below the minimum, sound speed increases again, as the effect of increasing pressure overcomes the effect of decreasing temperature (right).[26] For more information see Dushaw et al.[27]
A simple empirical equation for the speed of sound in sea water with reasonable accuracy for the world's oceans is due to Mackenzie:[28]
c ( T , S , z ) = a 1 + a 2 T + a 3 T 2 + a 4 T 3 + a 5 ( S − 35 ) + a 6 z + a 7 z 2 + a 8 T ( S − 35 ) + a 9 T z 3 , {\displaystyle c(T,S,z)=a_{1}+a_{2}T+a_{3}T^{2}+a_{4}T^{3}+a_{5}(S-35)+a_{6}z+a_{7}z^{2}+a_{8}T(S-35)+a_{9}Tz^{3},}
where
T is the temperature in degrees Celsius;
S is the salinity in parts per thousand;
z is the depth in meters.
The constants a1, a2, …, a9 are
a 1 = 1 , 448.96 , a 2 = 4.591 , a 3 = − 5.304 × 10 − 2 , a 4 = 2.374 × 10 − 4 , a 5 = 1.340 , a 6 = 1.630 × 10 − 2 , a 7 = 1.675 × 10 − 7 , a 8 = − 1.025 × 10 − 2 , a 9 = − 7.139 × 10 − 13 , {\displaystyle {\begin{aligned}a_{1}&=1,448.96,&a_{2}&=4.591,&a_{3}&=-5.304\times 10^{-2},\\a_{4}&=2.374\times 10^{-4},&a_{5}&=1.340,&a_{6}&=1.630\times 10^{-2},\\a_{7}&=1.675\times 10^{-7},&a_{8}&=-1.025\times 10^{-2},&a_{9}&=-7.139\times 10^{-13},\end{aligned}}}
with check value 1550.744 m/s for T = 25 °C, S = 35 parts per thousand, z = 1,000 m. This equation has a standard error of 0.070 m/s for salinity between 25 and 40 ppt. See Technical Guides. Speed of Sound in Sea-Water for an online calculator.
Other equations for the speed of sound in sea water are accurate over a wide range of conditions, but are far more complicated, e.g., that by V. A. Del Grosso[29] and the Chen-Millero-Li Equation.[27][30]
Speed of sound in plasma[edit]
The speed of sound in a plasma for the common case that the electrons are hotter than the ions (but not too much hotter) is given by the formula (see here)
c s = ( γ Z k T e / m i ) 1 / 2 = 9.79 × 10 3 ( γ Z T e / μ ) 1 / 2 m / s , {\displaystyle c_{s}=(\gamma ZkT_{\mathrm {e} }/m_{\mathrm {i} })^{1/2}=9.79\times 10^{3}(\gamma ZT_{e}/\mu )^{1/2}~\mathrm {m/s} ,}
where
mi is the ion mass;
μ is the ratio of ion mass to proton mass μ = mi/mp;
Te is the electron temperature;
Z is the charge state;
k is Boltzmann constant;
γ is the adiabatic index.
In contrast to a gas, the pressure and the density are provided by separate species, the pressure by the electrons and the density by the ions. The two are coupled through a fluctuating electric field.
Gradients[edit]
Main article: Sound speed gradient
When sound spreads out evenly in all directions in three dimensions, the intensity drops in proportion to the inverse square of the distance. However, in the ocean there is a layer called the 'deep sound channel' or SOFAR channel which can confine sound waves at a particular depth.
In the SOFAR channel, the speed of sound is lower than that in the layers above and below. Just as light waves will refract towards a region of higher index, sound waves will refract towards a region where their speed is reduced. The result is that sound gets confined in the layer, much the way light can be confined in a sheet of glass or optical fiber. Thus, the sound is confined in essentially two dimensions. In two dimensions the intensity drops in proportion to only the inverse of the distance. This allows waves to travel much further before being undetectably faint.
A similar effect occurs in the atmosphere. Project Mogul successfully used this effect to detect a nuclear explosion at a considerable distance.
See also[edit]
Acoustoelastic effect
Elastic wave
Second sound
Sonic boom
Sound barrier
Underwater acoustics
Vibrations
References[edit]
Jump up ^ Speed of Sound
Jump up ^ "The Speed of Sound". mathpages.com. Retrieved 3 May 2015.
Jump up ^ Bannon, Mike; Kaputa, Frank. "The Newton–Laplace Equation and Speed of Sound". Thermal Jackets. Retrieved 3 May 2015.
^ Jump up to: a b Murdin, Paul (25 December 2008). Full Meridian of Glory: Perilous Adventures in the Competition to Measure the Earth. Springer Science & Business Media. pp. 35–36. ISBN 9780387755342.
Jump up ^ Fox, Tony (2003). Essex Journal. Essex Arch & Hist Soc. pp. 12–16.
Jump up ^ Dean, E. A. (August 1979). Atmospheric Effects on the Speed of Sound, Technical report of Defense Technical Information Center
^ Jump up to: a b Everest, F. (2001). The Master Handbook of Acoustics. New York: McGraw-Hill. pp. 262–263. ISBN 0-07-136097-2.
Jump up ^ "CODATA Value: molar gas constant". Physics.nist.gov. Retrieved 24 October 2010.
^ Jump up to: a b U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C., 1976.
Jump up ^ Uman, Martin (1984). Lightning. New York: Dover Publications. ISBN 0-486-64575-4.
Jump up ^ Volland, Hans (1995). Handbook of Atmospheric Electrodynamics. Boca Raton: CRC Press. p. 22. ISBN 0-8493-8647-0.
Jump up ^ Singal, S. (2005). Noise Pollution and Control Strategy. Oxford: Alpha Science International. p. 7. ISBN 1-84265-237-0. It may be seen that refraction effects occur only because there is a wind gradient and it is not due to the result of sound being convected along by the wind.
Jump up ^ Bies, David (2004). Engineering Noise Control, Theory and Practice. London: Spon Press. p. 235. ISBN 0-415-26713-7. As wind speed generally increases with altitude, wind blowing towards the listener from the source will refract sound waves downwards, resulting in increased noise levels.
Jump up ^ Cornwall, Sir (1996). Grant as Military Commander. New York: Barnes & Noble. p. 92. ISBN 1-56619-913-1.
Jump up ^ Cozens, Peter (2006). The Darkest Days of the War: the Battles of Iuka and Corinth. Chapel Hill: The University of North Carolina Press. ISBN 0-8078-5783-1.
Jump up ^ A B Wood, A Textbook of Sound (Bell, London, 1946)
Jump up ^ "Speed of Sound in Air". Phy.mtu.edu. Retrieved 13 June 2014.
Jump up ^ Nemiroff, R.; Bonnell, J., eds. (19 August 2007). "A Sonic Boom". Astronomy Picture of the Day. NASA. Retrieved 24 October 2010.
Jump up ^ Zuckerwar, Handbook of the speed of sound in real gases, p. 52
^ Jump up to: a b L. E. Kinsler et al. (2000), Fundamentals of acoustics, 4th Ed., John Wiley and sons Inc., New York, USA.
Jump up ^ J. Krautkrämer and H. Krautkrämer (1990), Ultrasonic testing of materials, 4th fully revised edition, Springer-Verlag, Berlin, Germany, p. 497
Jump up ^ "Speed of Sound in Water at Temperatures between 32–212 oF (0–100 oC) — imperial and SI units". The Engineering Toolbox.
Jump up ^ Wong, George S. K.; Zhu, Shi-ming (1995). "Speed of sound in seawater as a function of salinity, temperature, and pressure". The Journal of the Acoustical Society of America. 97 (3): 1732. Bibcode:1995ASAJ...97.1732W. doi:10.1121/1.413048.
Jump up ^ APL-UW TR 9407 High-Frequency Ocean Environmental Acoustic Models Handbook, pp. I1-I2.
Jump up ^ Robinson, Stephen (22 Sep 2005). "Technical Guides - Speed of Sound in Sea-Water". National Physical Laboratory. Retrieved 7 December 2016.
Jump up ^ "How Fast Does Sound Travel?". Discovery of Sound in the Sea. University of Rhode Island. Retrieved 30 November 2010.
^ Jump up to: a b Dushaw, Brian D.; Worcester, P. F.; Cornuelle, B. D.; Howe, B. M. (1993). "On Equations for the Speed of Sound in Seawater". Journal of the Acoustical Society of America. 93 (1): 255–275. Bibcode:1993ASAJ...93..255D. doi:10.1121/1.405660.
Jump up ^ Kenneth V., Mackenzie (1981). "Discussion of sea-water sound-speed determinations". Journal of the Acoustical Society of America. 70 (3): 801–806. Bibcode:1981ASAJ...70..801M. doi:10.1121/1.386919.
Jump up ^ Del Grosso, V. A. (1974). "New equation for speed of sound in natural waters (with comparisons to other equations)". Journal of the Acoustical Society of America. 56 (4): 1084–1091. Bibcode:1974ASAJ...56.1084D. doi:10.1121/1.1903388.
Jump up ^ Meinen, Christopher S.; Watts, D. Randolph (1997). "Further Evidence that the Sound-Speed Algorithm of Del Grosso Is More Accurate Than that of Chen and Millero". Journal of the Acoustical Society of America. 102 (4): 2058–2062. Bibcode:1997ASAJ..102.2058M. doi:10.1121/1.419655.
External links[edit]
Calculation: Speed of Sound in Air and the Temperature
Speed of sound: Temperature Matters, Not Air Pressure
Properties of the U.S. Standard Atmosphere 1976
The Speed of Sound
How to Measure the Speed of Sound in a Laboratory
Teaching Resource for 14-16 Years on Sound Including Speed of Sound
Technical Guides. Speed of Sound in Pure Water
Technical Guides. Speed of Sound in Sea-Water
Did Sound Once Travel at Light Speed?
Acoustic Properties of Various Materials Including the Speed of Sound
Technical Guides - Speed of Sound in Pure Water (provides a calculator for the speed in water)
Discovery of Sound in the Sea (uses of sound by humans and other animals)
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District planning in India
From Wikipedia, the free encyclopedia
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District Planning is the process of preparing an integrated plan for the local government sector in a district taking into account the resources (natural, human and financial) available and covering the sectoral activities and schemes assigned to the district level and below and those implemented through local governments in a state.[1]
District is the most suitable administrative unit for decentralized planning below the state level as it possesses the required heterogeneity and is small enough to undertake people in planning and implementation and to improve productivity; district planning is an important tool.
With the 73rd and 74th amendments[2] of the Constitution of India, decentralization of planning is emphasized and the methodology of district plan was changed. The approach suggested for the preparation of the district plan is as follows:-.[3]
Contents
[hide]
1 Steps in district planning
2 village visioning
3 Block vision
4 Plan for grama panchayat/municipality
5 Plan for block panchayats
6 District plan
7 Integration of entire local plans
8 Summary of district planning methodology
9 See also
10 References
11 External links
Steps in district planning[edit]
The sequence in the preparation of district plan can be as follows
Preparation of district vision, block vision and gram panchayat level vision.
Preparation of participatory plan involving Gram Sabha from Gram Panchayats to Zilla Parishad.
Preparation of plans by Urban Local Bodies.
Consolidation of plans prepared by local bodies by District Planning Committees.
Planning starts with the preparation of vision documents by local bodies.[4]
village visioning[edit]
A vision document is for 10 to 15 years is to be prepared by the district and for each local government based on a participatory assessment. The DPC may hold formal interactions with local governments and other key stakeholders on this and then finalise it. The document should clearly identify the key reasons for backwardness / development shortcomings and address issues impeding development.
District vision document will cover :-[5]
Agriculture and allied sectors.
Availability and development of water sources.
Industries – especially traditional, small industries including food processing.
Infrastructure including power.
Drinking water and sanitation.
Literacy, school education.
Health and medical facilities.
Poverty reduction and basic needs.
Gender and children.
Social justice – SC / ST, Persons with disability etc.
To assist the DPC in preparing the vision document (and subsequently to vet the draft plan proposals), a Technical Support Group may be constituted in each district. it may consist of departmental officers nominated for the purpose in addition to their duties or retired persons locally available or a local academic institution or established NGO with a proven record – similarly, technical support as appropriate, may be organized for the urban areas, intermediate panchayats and village
If undertaken in a campaign mode, the preparation of vision documents can be completed in two months time.
Further, if District is to be the economic unit for planning exercise, the scope of vision document could be expanded to include areas of comparative advantage of each district which would be the basis for attracting private investment.
Block vision[edit]
After finalizing the vision document for the district at the district level, the document will be discussed at the block level and a vision document for the block will be prepared with some modifications based on the conditions of the block. The vision document for each block need not be completely different because the agro-ecological conditions of some planning units at this level may be same, particularly when a district is divided into a large number of Inter Mediate Panchayats as in the case of Andhra Pradesh. Even though the same vision is adopted for some blocks / mandals, it is necessary to have the vision owned by the Intermediate Panchayat. This exercise will be done by a team of experts at block level. The same team will be responsible for plans at the GP level. However, the team will take some members like professionals or retired persons belonging to the area to assist the team in the preparation of the plan. The general formats for planning at the lowest unit level viz., GP or ULB will be prepared at the district level and they will be adopted with certain modifications at the block level.
Vision of the Gram Panchayat will also be prepared accordingly. The vision of the GP will be based on the Socio-economic Profile of the GP and views of the GP.
Plan for grama panchayat/municipality[edit]
At the third stage, the plan at the GP or ULB will be prepared. This will be prepared by the team with the help of people's participation. The will first interact with the GP and prepare a vision on the lines of the district vision. Once the Gram Panchayat vision is approved, the team will conduct several Group Discussions to find out the potentials, needs and constraints of the village economy in Gram Sabha. The felt needs of these communities and the support needed for improving their livelihood conditions will be elicited. Once this exercise is completed, it will be discussed in the Gram Sabha. This approach will help to study the situation thoroughly and prepare the plan. In particular, all the schemes CSS State sponsored schemes will be examined thoroughly with a view to understand their suitability to the area. This can be more easily ascertained from the beneficiaries/stake holders. The plan should also take into account the long term development perspective of the GP and also natural resource management (NRM) aspects.
Plan for block panchayats[edit]
The above three steps followed the top down approach in the preparation of the district plan. After this GP Plan is prepared and no plan is ready at higher levels except the vision. The Plans at the higher levels will be prepared in the next steps. In this step, the GP plans will be consolidated and put before the IP. In the GP plans, the benefits of some of the schemes will go beyond the GP and such schemes may figure in the other GP plans also. Hence, they have to be separated and duplication has to be avoided. Similarly, some schemes which provide benefits beyond the GP level may not be identified in any GP. The Block Plan has to identify those schemes / projects. This exercise will be done at the meetings of the Intermediate Panchayat level.
District plan[edit]
The final stage is the preparation of the district plan. This will be finalized after the Block Plans are finalized in the same way as the Block Plan is finalized on the basis of the GP Plans in the Block. The schemes that will not figure in the Block Plans, but are essential for the development of the district will be identified at this stage. Further, an attempt will have to be made to achieve functional and spatial integration and use the norms for the provision of social infrastructure. The above five steps will help in the preparation of the perspective plan. To work out the annual plans, the financial resources available have to be taken into account. The local government component of the District Plan would emerge from the resource envelope containing the following sources of funds:
Own resources available for development
Transfers by State Finance Commission for development purposes
Twelfth Finance Commission grants passed on by the State Government
Untied grants for local planning
Grants in respect of Centrally Sponsored Schemes.
Grants for State Plan schemes assigned for implementation through local Governments
Grants for externally supported schemes assigned for implementation through local governments
Estimated contribution by the communities themselves
The document that embodies this statement of resources and their allocation for various purposes is known as the District Plan. It would essentially have three aspects namely.
Plan to be prepared by the Rural Local Bodies for the activities assigned to them and the national / state schemes implemented by them with their own resources and those earmarked for these purposes;
Plan to be prepared by the Urban Local Bodies for the activities assigned to them and the national / state schemes implemented by them with their own resources and those earmarked for these purposes;
Physical integration of the plans of Rural and Urban Local Bodies with the elements of the State Plan that are physically implemented within the geographical confines of the district.
Integration of entire local plans[edit]
In the realization of the district vision, district plans will need to put together resources channelised from all sources including district segments to the State Plan, CSSs, Special Programmes such as Employment Guarantee, Sarva Shiksha Abhiyaan, Rural Health Mission, Grants-in-aid for specific purposes from Finance Commission, Bharat Nirman etc. Therefore consolidation is a task that goes much beyond compilation and connotes a degree of value addition through integration of local plans. There are several aspects of integration of plans that have to be considered in the preparation of the draft development plan. The different dimensions of integration have been discussed very succinctly in the planning guidelines[6] for local bodies in Kerala as detailed below and could be adapted for general use:
Spatial integration
This would mean integration of schemes such as roads that run through one or more Panchayats. Such kinds of Multi Panchayat infrastructure projects could be taken up with proportionate contributions from the Panchayats concerned dovetailed into the funding available from above and entrusted to one local government for execution.
Sectoral integration
This relates to the integration that takes place within a sector. For instance, an integrated approach to agricultural development would require the integration of several schemes relating to agriculture, such as horticulture, drip irrigation, high yielding varieties and integrated pest management.
Cross-sectoral integration
To ensure maximum impact from different interventions, it is necessary to design approaches that draw resources from various schemes. For instance, a good approach to public health would require inputs from water and sanitation allocations and health programme allocations. Again, a typical watershed management programme would comprise soil conservation, water harvesting, micro irrigation, bio-mass generation, fisheries, animal husbandry, agro processing and micro enterprise components, all properly sequenced.
Vertical integration
This is based on the precept that District and Intermediate Panchayats ought to perform activities which have the advantages of scale and which cannot be done by the lower tiers of local government. This will require that Block Panchayats have a clear idea as to what the draft plans of Village Panchayats will contain, Similarly the District Panchayats would need to consider the approved plans of Village and Block Panchayats before finalizing theirs.
Integration of resources
There are several schemes both Centrally sponsored and State sponsored which Panchayats can utilize, integrate into local plans and to which they can contribute additional resources. This would comprise two aspects, as below:
Integration with State Plans
There are several State Plans, which as implemented can be strengthened by increased allocation from Panchayat funds. In some cases a component having a complementary nature could be added to the State Plan Scheme. For instance, the drawing of electric wires to villages could be complemented by the Panchayat taking up the wiring of BPL houses.
Integration of CSSs with local plans
It is important that in the interest of efficient use of resources, there ought to be only one development plan for the local government prepared through a common planning process and not a set of separate plans prepared in accordance with the guidelines of each programme. Thus once priorities and works are identified and prioritized through a single planning process, components pertaining to a particular sector could be taken up through schemes, including CSSs while still keeping within the guidelines of those schemes.
Integration with local resources
Planning can provide for local investments to be catalysed through local resources or initiatives. For example, village knowledge centers and Rural business Hubs could be catalysed by Panchayats. This is also possible by extending the concept of Pura to encompass the concept of rural business hubs. By this, we do not meant that Panchayats ought to run industry locally, but that it catalogs local skills and natural resource endowments and facilitate the development of business linkages.
Rural Urban Integration
Integration of urban-rural plans, which is particularly important in the light of increasing urbanization, is an area where the District Planning Committee could contribute a great deal. The DPC should work out mechanisms of joint programmes to be financed by State government institutions and joint contributions by urban and rural local bodies.
Summary of district planning methodology[edit]
In short, the district planning start with a vision and end up in an integrated plan for the district. Preparation of a district vision is the first significant event in district planning. On the basis of district vision document, a plan will be prepared at the Gram Sabha level. The Gram Panchayat may finalise its plan based on prioritise exerging from the Gram Sabha and earmarking suggestions for the Intermediate Panchayat. Projects and activities which can be implemented at the Gram Panchayat level should be included as “Gram Panchayati Plan”. Those projects and activities which can be implemented only in more than one Gram Panchayat, will be forwarded to the Intermediate Panchayats to be considered for inclusion into the “Intermediate Panchayat Plan”. The Gram Panchayat plans should also provide an estimate of the community contribution that can be mobilized for the purpose of implementing the development plan.
Based on these suggestions received from Gram Panchayats and its own priorities the Intermediate Panchayat should finalise its plan. Projects and activities, which can be implemented at the Intermediate Panchayat level should be included as “Intermediate Panchayat Plan”. Those projects and activities which need to be implemented in more than one intermediate panchayat will be forwarded to the District Panchayat to be considered for inclusion into the “District Panchayat Plan”.
Based on the Gram Panchayat Plans, the intermediate Panchayat Plans and District Panchayat Plans, the District Planning Committee shall finalise the District Plan for the district and will form part of the State plan.[7]
See also[edit]
District Planning in Kerala
District Planning Committees in India
List of planning agencies in India
References[edit]
Jump up ^ For a detailed understanding of the concept of district planning see District Planning Lessons from India, Rome, FAO,1995 [1]
Jump up ^ See 74th Constitutional amendment act 1994</ [2]
Jump up ^ See the Drsft guidelines for the preparation of district plan, Govt of Assam, Panchayat and Rural Development Department, Dispur , Guwahaty
Jump up ^ See Manual for integrated district planning, New Delhi, Planning Commission, 2008 PP 51 - 132
Jump up ^ Guidelines for district plan in the eleventh five-Year plan
Jump up ^ See Guidelines for decentralized planning in local governments of Govt of Kerala for eleventh five-year plan, Govt Order(MS) No. 128/2007/LSGD, dated,14-05-2007, "Archived copy" (PDF). Archived from the original (PDF) on 2008-11-22. Retrieved 2009-01-30.
Jump up ^ District planning in Kerala : The concept , history and procedures by K Rajasekharan, In T M Joseph : Decentralized governance and development, New Delhi, Deep & Deep,2009 P 214 -241
External links[edit]
Manual on Integrated District Planning, Planning Commission of India, 2008
District planning lessons form India Rome, FAO,1995
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