Hey, here's an off-topic thing that caught my interest. I hope maybe you'll have some input.

I'm wondering where the onset of non-linear distortion happens from compression/rarefaction asymmetry. Do you happen to know of any references to reliable research data on the subject?

I'm guessing it happens when the compression cycle of sinusoidal pressure reaches 1.5 to 2 atmospheres, 'cause that would put the rarefaction cycle between 0.5 and 0.0. This assumes (1.0) atmospheric pressure is the baseline, 'cause I'm wondering where the start of trapped-air distortion and other air pressure related acoustic nonlinearity begins. Since you can't go below 0.0, but you can go above 2.0, somewhere in the 1.5 - 2.0 range must start the onset of asymmetry. I just don't know where it is.

Check this out. Let me know if you know of any good data on the subject.