Ultrasonic Microphone

[concrete_hed]

Just recently my dog has been acting strangely and i discovered that it was the smoke alarm that was upsetting her. Sometimes i hear the smoke alarm making all sorts of strange tones. I think that the smokealarm is making a tone that is above humans hearing range but not that of a dogs. I have tested my hearing and i can hear up to 18khz only just.

 

I tried replacing the battery of the alarm but it still upsets my dog. So clearly the smokealarm is stuffed but i want to figure out whats making my dog all mental.

 

Does anyone know how i can make a microphone that will be able to pick up 18khz and above tones? Is it possible to use this microphone with my computer sound card to record the noise?

[swansont]

The limit is probably not in the microphone, so if you have an oscilloscope program you could look at the data.

[concrete_hed]

Yes i do have an oscillascope program, i have a normal computer microphone put it doesnt pick up anything when i hold it right near the smoke alarm. I do just happen to have a pair of ultrasonic reciever things that are hooked up to my "RealRobots" robot. All it is, is a small speaker about 5mm diameter. I was thinking that i could make a microphone from these using an audio transformer. Can anyone tell me if this would work?

[swansont]

What's the response of the o-scope program? I recall one I used in grad school cut off at 20 kHz, and if yours has a similar limitation it's not going to work properly. It would also be useful if you could test the microphone at a few known frequencies to make sure it actually does respond as expected.

[YT2095]

the RR transducers do indeed work (I have 2 robots here), don`t use a transformer to couple it though!

 

a simple FET or high gain transistor will be just fine. Treat it as you would an ordinary electret mic.

 

then make sure all your setting are at least 30khz and below Pass, Above 30K and you`ll find a simple Field strength meter will work