Like Krazor said, piezoelectric crystals would work --
Piezoelectric ceramic transformers are an exciting alternative to conventional wire-wound transformers which use electromagnetic coupling to increase voltage. A piezoelectric transformer generally consists of an input and an output resonator, which are acoustically coupled, but electrically insulated. When an electrical signal near the frequency of mechanical resonance is applied to the input section of the transformer, strong mechanical vibration occurs due to the piezoelectric converse effect. This vibration is then transferred to the output section, inducing a voltage on its electrodes due to the piezoelectric direct effect, with a consequent gain. This technology uses an advanced interdigitated electrode design, so that electrical connections are made at vibration nodes. This leads to a significant increase in reliability. The advantages of high voltage, ease of miniaturization, high frequency, low electrical noise, large degree of insulation, high efficiency, and low expense are important in many emerging microelectronic, photonic, sensor, and display applications.
http://www.yet2.com/app/utility/externa … hpak/25444
This shows that piezeoelectric materials are capable of transferring, and thus generating, appliance level power. But as discussed on this thread, the problem is that ordinary sound by itself doesn't carry much energy. Here's a good page on waves and sound:
http://sol.sci.uop.edu/~jfalward/wavess … sound.html
There's a table there that shows if you capture one square meter's worth of sound at conversation level, you can generate no more than .000006 watts of electricity. But this becomes 100 watts with sound at the loudness of a jet engine.
But if you use sound as a trigger that opens a gateway to a different source of energy, then that's something else entirely. Tapping sound for energy is like tapping the energy in a switch-flip, but using sound to tap energy is like flipping the switch and turning on the mains electricity.
The crystals used for serious healing and meditation purposes tend to be Vogel Cut crystals, which are crystals cut in a taper with two pointed ends, one end being more blunt than the other. Somehow this is optimized for internal resonance and energy transfer. Read more about these here:
http://www.vogelcrystals.net/legacy_of_marcel_vogel.htm
For mechanical resonance that taps into the zero point energy, say by using sound as the trigger, check out this awesome article:
http://www.terraresearch.net/articles/GodsFirmament.htm
Acquiring fringe knowledge is like digging for diamonds in a mine field.
