". . . doorbells you can't hear"
A relay with a high impedance coil controlling a much larger 120v doorbell?
Relays have "current gain" so find one that has a high ratio of
contact current rating/coil current rating.
"The NFPA 72 requirement for sleeping rooms is either a minimum of 75 dBA or 15 dB over the average ambient sound level, whichever is greater."
is probably for 1 meter distance. You lose 6 dB for each doubling of distance.
"Near total silence - 0 dB
A whisper - 15 dB
Normal conversation - 60 dB
A lawnmower - 90 dB
A car horn - 110 dB
A rock concert or a jet engine - 120 dB
A gunshot or firecracker - 140 dB"
and an airbag comes in at 175 dB and probably deafens you while it saves your life.
Last edited by Wuzzat?; 10-10-2012 at 01:25 PM.