Originally Posted by Merlosso
If we were floating 10,000 feet off the ground, not moving, with no clouds or wind, and I was facing a one of these loud Harleys 5 feet in front of me, would I hear none of the sound coming out of the tailpipe? With nothing for the sound to reflect off of, would it then not make any difference what kind of exhaust the motorcycle had? If I'm understanding this correctly, I would hear some sound from the engine but not the sound directed out the exhaust pipe.
OK, I'm not challenging you on this. I'm just curious.
My response to the question would be yes. In a perfect anechoic environment you would not hear the exhaust from the bike if you were not in the path of the wave (i.e. standing in front of the bike).
I can provide an example to illustrate the point. On those quiet nights at home when you hear one of those loud bikes in the distance
you will notice that you only hear the bikes that are moving away from you, never toward you. This is because the bikes are far enough away that the reflected waves never make it to your location, but the direct waves continue to travel until they are attenuated by the atmosphere as a result of distance. If those direct waves magically 'wrapped around' the bike you would hear approaching bike also.
Also, please do not feel that I would think that you are challenging me. I am happy to answer questions, especially to help clear any misinformation. This is why I try to explain my answers. Bearing in mind, sometimes I can be wrong. Thanks