I am a certified American sign language interpreter in my state and also coordinate various free electrical services for my local Deaf community.
During a recent conversation with a Deaf friend he mentioned that he has no way of knowing whether or not his vent fan is on for his stove. I began pondering an electronic solution. A microphone with a simple amp and a bandpass filter for the fan frequency would work right? Then I could simply use a row of LED's for each sound detection frequency, but I was wondering if the bandpass solution would work for all fans and how interference may affect the accuracy.
Some of you may remember a long time ago when I tried to use microphones to detect horns and sirens while driving in traffic. This was also a "Deaf aid".
In an effort to simplify the process I have even considered tuning forks modified inside a coil for each specific frequency rather than using microphones...this is where your mind takes you when you are not an electronic engineer!! lol
Any thoughts would be appreciated!