I am not disagreeing with you, but please explain your "math" a bit more. Are you saying that larger pipes result in a longer wavelength that create natural, or resonant, frequencies at a lower (cruising) or higher rpm? I would suspect that having a 40 series Flowmaster was a significant part of the noise. Flowmasters are designed more to create a particular sound than to muffle the engine noise.
I was just waxing philisophically about air flow through a tube, regardless of the style of muffler, or lack there-of...It is llike a pipe organ, larger diameter tubes will resonate at a lower natural frequency than skinny tubes. I.e. a 40 series with a 3 inch diameter pipe after it will sound a few Hz lower (or deeper) than same muffler with 2.25 inch diameter pipe after it.
I suppose if you were mental and really cared that much, you could select your favorite tone muffler and use pipe length and diameter to tune the octave range to just where you liked it. Just one more way you can look at our beautiful toyotas as a work of art (or in this case music).
