Record audio above human hearing frequency-- how?

[lee321987]

Hello, I need to build a circuit that can record audio frequencies up to 45kHz.

I have two main questions:

1) What kind of microphone do i need?
2) What kind of circuit do I need in order to make these sounds audible to a human? A circuit that can lower the input frequencies by about 20kHz (microcontrollers are fine).

Thank you very much for any help!

 

[keith1200rs]

Knowles MEMS microphones work up to ultrasonic frequencies but I am sure there will be others.

To listen to ultrasonic frequencies I assume you would remove audible frequencies and then shift the ultrasonic range down. So, first filter out anything below say 25kHz. Then mix the signal with 20kHz and maybe low pass filter.

Keith

 

[FvM]

Knowles MEMS microphones work up to ultrasonic frequencies but I am sure there will be others.

Knowles would be a cheap solution. You also have B&K microphones with up to 140 kHz frequency range, high performance and rather high price.