Accoustic wave propagation and effects in a tube

[allblowdup]

This is my first post and I'll admit I probably don't even know enough to be dangerous. Any how what I have is a a 3' long 6" dia tube that is functioning as a muffler for a boat. It has two 4" dia inlets mounted perpandicular to the length of the tube at 28" on center and two 4" oulets mounted perpendicular to the length of the tube at 12" on center on the opposite side. It is a v8 engine and from I can tell the sound waves that come into the muffler design end up being 180deg apart. The problem is a weird one in that the muffler is to quiet as some exhaust note is preferrable.

If the waves are colliding in the middle of the 3' long tube could I just extend one end of the tube to effectively un balance the wave activity? If so how far would I need to go. Like I said I am not knowledgeable with this at all but there must be a reason for the sound cancelation. I do know that if I was to move the outlets closer together the exhaust note is increased. Unfortionaly I cannot in this case. I can add a third outlet in the middle though.

Mark

 

[PhilDSP]

To produce almost a similar effect to lengthening the tube you could stuff one end with dense non-flammable material like steel wool (temporarily while you carefully monitor the situation). But since the material would be porous you'll also get a dampening of the sound but with some reduction of the high frequencies compared with the low frequencies. (That's probably what you're looking for, a low frequency growl)

I think some after market car mufflers used fiberglass in sections of the mufflers to produce that kind of dampening - "glass packs".

 

[allblowdup]

That is correct. In this application the noise is already to quiet. With this tube muffler could it act as a standing wave tube and for some unknown reason I have got the outlets positioned where the nodes would be?