whistle key finder project (or audio response)

Thread Starter


Joined Oct 25, 2007
Hey there, new to this forum but it looks great :)

Basically I have a project fo finish by next wednesday, I am building a prototype circuit on a breadboard (or two), and probably won't be making it on an actual pcb or anything.

The task outline was to design and build a useful test widget, it could be capable of detecting anything from a sound, to light or temperature, to a rise in water level.
In my task I chose to make some sort of whistle key finder, something that responds to a sound and outputs.
Sounds pretty simple but to make it slightly more complicated the final aim for me would be to make it respond to claps to turn it off, and to make it output the output constantly after soemthing like 5 consecutive whistles (but all this doesnt matter just yet, as the first most important part is to get it responding correctly to sounds).
the output would be an LED and a buzzer.

My original start design was something like:
mic>amp>RC filter>comparator>monostable then somehow connected a 555 timer and a logic gate or somethig.

so far ive got to the monostable, and am in the process of configuring that correctly so that it operates correctly.

Currently the problem im facing is switching around the RC circuit i implemented to a high pass filter instead. I realise I could use something else in its place but Im under a time limit here and probably a CR circuit or something similar would fit it fine in the time.
Also if i do get the chance to go further and implement other functions ot it (like clapping to turn it off) then I haven't thought that through at all yet!

So far this has been a big learning curve for me and it's sort of a 'thrown in the deep end' thing for me as im just starting my 1st proper year of electronic engineering, and I really would appreciate any help that anyone can give, and maybe in the future when I am more learned I can give out what I've learnt also :)

Cheers for any help guys!


Joined Jan 22, 2004
here's a circuit i have never come to build which i would also like to do. this was designed by my fellow country man. it uses a 4069 and 2 transistors and piezo buzzer. it's a simple set up.