Voiceless alveolar trill

The voiceless alveolar trill differs from the voiced alveolar trill in its phonation (whether or not the vocal chords are vibrating while pronouncing the sound). It is used in a few languages. In languages that also have the voiced alveolar trill, it can be a similar sound or an allophone (another way a certain sound can be pronounced).
In Proto-Indo-European, the sound *sr became a sound spelled , with the letter for and the diacritic for , in Ancient Greek. This sound was probably a voiceless alveolar trill. It became the regular word-initial (meaning "at the start of a word") allophone of in standard Attic Greek. This sound has disappeared in Modern Greek.
Features.
Features of the voiceless alveolar trill:
Voiceless alveolar fricative trill.
The voiceless alveolar fricative trill is not known to be a sound in any language, except maybe the East Sakhalin dialect of Nivkh. However, it is an allophone (another way of pronouncing a specific sound) in Czech.
Features.
Features of the voiceless alveolar fricative trill: