def each
      pos = 0
      while(pos < @original_duration) do
        chunk = nil
        begin
          chunk = Chunk.new(@original_file, @original_duration, pos, (@chunk_duration + @overlap), @rate)
          yield chunk
          pos = pos + [chunk.duration, @chunk_duration].min
        ensure
          chunk.close_file if chunk
        end
      end
    end
def each
      pos = 0
      while(pos < @original_duration) do
        chunk = nil
        begin
          chunk = Chunk.new(@original_file, @original_duration, pos, (@chunk_duration + @overlap), @rate)
          yield chunk
          pos = pos + [chunk.duration, @chunk_duration].min
        ensure
          chunk.close_file if chunk
        end
      end
    end
return temp file for each chunk