"sympathetic vibrations".
these are pretty cool-- here is a neat trick when watch a tv commerical-- (you should be at least 6 to 8 back from the tv for this to work.)
watch the tv , take a couple of deep breathes, and then, start to hum-- on middle c- (a piano is a nice start-- or some one with a good sence of pitch) Hum and watch the televisions.
Most human skulls have sympathetic vibrations with middle c, which also happen to have sympathetic vibrations with 60HZ-- TV screen are "refreshed" at a rate of 60 hz-- so after a while what happens in you can "See the the refresh rate" (this also happens when you make a tape recording of a TV broadcast) it distorts the image in an interesting way... it works for about 85 to 90% of the populations-- I used to know all the math (ie, frequecy of Middle C in Hz, most common frequency of human skull, etc.) but like Musick trick with the piano-- you can experient with sympathetic vibrations.
I have also heard that the "Throb" or bass beat of a lot of rock 'n roll is a sympathetic vibrations to the human heard beat-- so music can actually effect your heart rhythm.... so Wow, you might be "too old" -- music that once moved you, might now give you pain....
