is there a certain hertz or sound that if you make it everything will be silent like you can hear your self or other when talking i am not talking about something really loud i was thinking of something pretty unoticable today i was sitting down and something in a truck right before it started mad like a really high pitch sound almost unoticeable and it made everything quiet i could barely hear does any one know how you can acheive this and possibly have schematics or a chip board lay out thanks mike