Pipes and velocity of sound?

Question

is it necessary to use the effective length of pipes or would the acutal lengths be adequate when calculating the velocity of sound?

Answer 1

The velocity of sound is independent of pipe's length. Frequency however is a different thing it is inversely proportional to the pipe length.

f=nc/(2L)  n = 1, 2, 4, 6

f=nc/(4L)  n = 1, 3, 5, 7

n - hormonic

L pipe length

c- speed of sound

This implies that a pipe with a fixed length has only certain resonant ( i.e. audible) frequencies.  This is the principle behind organ pipes, where many different lengths are needed to produce all frequencies.