DelphiYet the company includes a travel case with generous storage compartment? What situation would the intended user find themselves in where it would not be possible to have 2xAAAs? Just trying to figure out the mechanics and target market of this item...it is definitely different.
LxJLthrSmall resonance chamber behind the bridge with the piezo pick-up. The stethophone allows air movement to be transmitted between that chamber and your ear bones. Pretty much the same system that airlines used for decades when you paid to hear the in-flight movies. No electronics, no batteries needed. It just needs a relatively air-tight closed pathway.
Personally, I would use my Line-6 Pocket Pod with phones rather than the stethophone.
Same this with portable amps, there are plenty portable ones like one below that don't take up any space and power everything short of 250Ohm+ cans...
Just curious...
http://www.amazon.com/AP2BS-amPlug-Bass-Guitar-Headphone/dp/B00NAUKJTY/ref=sr_1_18?ie=UTF8&qid=1463175687&sr=8-18&keywords=portable+guitar+amp