High Efficiency Speaker Asylum

RE: So does sound really slow down in a stuffed tapered Transmission line??

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In Reply to: RE: So does sound really slow down in a stuffed tapered Transmission line?? posted by Artesmio on September 10, 2007 at 14:19:37

A tapered pipe will have a lower resonant frequency compared to a straight pipe of the same length, that is the "trick" for getting a short tapered pipe to have a lower then expected tuning frequency. That is also the "trick" that caused people to believe that the speed of sound had dropped significantly in a stuffed TL.
The classic formula f = c / (4 x L) only works for a constant area straight TL, it is not accurate for a tapered TL (1/4 wavelength frequency will be lower) or an expanding TL (1/4 wavelength frequency will be higher). It is not accurate for a TL with a choked or ported open end.
Fiber stuffing only slows the speed of sound very slightly, the lowest value I use is 320 m/sec for 1 lb/ft^3 of stuffing density compared to a free air value of 344 m/sec.

Edits: 09/10/07 09/10/07

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