Why does a tubes length affect wavelength of soundwave?

[physicsnnewbie]

In a wind instrument for example. Wouldn't a longer tube simply allow more compressions/rarefactions to be moving through the tube at anyone time? Why does the wavelength change?

 

[Doc Al]

Because only only certain wavelengths--ones that depend on the length of the tube--get reinforced enough to persist. Other wavelengths quickly die out. Read about how standing waves are formed here: http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html#c1"

 

[Astronuc]

In a wind instrument for example. Wouldn't a longer tube simply allow more compressions/rarefactions to be moving through the tube at anyone time?

If one tube has length L, and another tube has length L+l,where l is the wavelength, then L+l has one more wave in the tube, but the speed of propagation (speed of sound) is a property of the gas in the tube, not the length of the tube.