View Full Version : Electronic Hearing ?

May 20, 2002, 09:00 PM
Since electronic mufflers use an opposing wave of equal magnitude to cancel out the incoming sound, wouldn't that cause damage to your ear even though you can't "hear" it?

May 20, 2002, 11:18 PM
No.....the pressure pulses are out of phase and equal amplitude: ideally canceling out, resulting in zero pressure.


Jim Watson
May 20, 2002, 11:22 PM
Electronic shooting muffs do NOT use out of phase noise cancellation; that only works well for continuous sound, most usually seen in aircraft headsets. A gunshot is a single impulse not subject to being canclelled out.

All that electronic shooter's ear protection does is provide amplification to get ambient sound, like range commands, "past" the insulation of the muff. The amplification shuts off in some models, down to a minimum level in others, as incoming sound above a set value is detected, leaving the gunshot to be attenuated by the muff. When the battery runs down, they are as effective protection as ever, you just don't hear background sound and conversation, same as a plain muff. So there is no extra energy from a cancelling sound wave to be dealt with.

In the aircraft style of noise cancelling headset, the small amount of energy in the out of phase sound waves added to the outside noise probably shows up as a tiny amount of heat. As C.R. says, there is no pressure difference, but the energy has to go somewhere. I do not think it ends up in a capacitor in the power supply as Arthur C. Clarke wrote in one of his White Hart S.F. stories.

May 21, 2002, 12:36 PM
Ooops.........wrong application of wrong gear. Me sorry.

Thanks for catchin that Jim.