Ultrasound recording


I have recently discovered a colony of bats living in my barn and would like to record their sounds - ideally without spending much/anything!

Is there a way of using or adapting a standard microphone and using audacity (running on linux) to do this?

A quick trial wasn’t successful, but is this because it is impossible without specialised transducers/microphones or because I haven’t got it right?

Thanks for any help or advice you can give.


This has come up before, with limited success.

Most microphones will not respond to sound up that high because it is in the financial interests of the makers to prevent them from doing so. Any time a microphone responds to “sound” that you can’t hear, there are problems, so this response tends to be restricted.

Many sound cards will not pass audio beyond the audible top or about 20,000 Hz. That costs money to do and very few people will need or appreciate it. People shopping for a sound card usually stop looking at around $25. You don’t get a lot of sophisticated sound card for $25.

Then there is the sampling problem. Audacity defaults to 44100 sampling rate at 32-bit floating. The floating business is fine, but the 44100 business will not do it. That’s the sampling frequency chosen for Audio CDs and it will just barely pass the highest tone in an orchestra without damage.

That number needs to be substantially higher (2 to 2.6 times) than the highest frequency in the show.

How high do bats normally talk? If we assume 35000, then the sampling frequency needs to be around 91000. I think 96000 is a standard rate.

We told the other user to go buy (sorry) a “silent” dog whistle and use that for testing. See if it will tell you on the package what the frequency is.


Hi Koz

Thank you very much for the very informative answer.

I’ll put a few bat boxes up and if I get a positive response (from the bats, that is) then I’ll have a go at getting a proper transducer and sound card, etc.

Thanks again