Hi Lazymut,
The tests Jay is referring to were conducted in a studio last year. I have the full results available if anyone is interested pm me and I will send them in an email.
As has already been said. Its all about frequency rather than volume, ie: the lower the frequency the greater the response. I could not test lower than human hearing as the tone generator only went as low as 20Hz.
Without getting to technical its all about transverse and compression waves and the effect on the axies lateral line. Which is similar to that of other species in particularly sharks. It allows the axie to sense vibrations and electrical fields.
So a low sound has a long sound wave, (about 15meters for 20Hz and about 1 meter for 1kHz normal male human speaking is around 630Hz - 1.2 kHz) Low sound Longer cycle, High sound shorter cycle.
Elephants can communicate over vast distances using subsonic frequencies. Music like Tool and Bioshock have an abundance of bottom end so does a lot of hip hop. We tested using pure tones ie: sine waves not music.
Any way to summarize Lots of bass and lows = bad
Good luck