How to eavesdrop on your pets using technology

November 12, 2012 9:17 AM

Rabbits may vocalize in frequencies humans can't hear. How can I record my rabbits talking and play it back to myself?

They're quiet, but rabbits do talk. They growl when angry or threatened, they make a honking/huffing noise when they are very excited, and they will scream when they think they are in mortal danger. Those are all noises you can hear easily if you are paying attention.

However, sometimes my house rabbits will do things that make me think they are talking to each other, but I don't hear anything. For example, one rabbit is behind the couch and the other is in the middle of the room--they can't see each other, but suddenly they swivel their ears to each other and both make the same motion. Rabbits can hear sounds in frequencies of 360-42,000 Hz whereas humans can hear 64-23,000 Hz so I suspect they are speaking in frequencies I cannot hear.

I would like to somehow record my rabbits talking to each other and play it back in a range that I can hear. Is this possible, and what would the best way to do it be? I have no experience with sound recording and no idea of what kind of equipment or software would be useful. The rabbits themselves are pretty tame, live in my apartment, and would put up with me doing weird things around them, fwiw.

posted by epanalepsis to grab bag (6 answers total)

There are devices called bat detectors that pitch down bat vocalizations into human-audible frequencies. People have used them to listen to their pet rats, maybe the same can be done for rabbits.
posted by RobotHero at 9:45 AM on November 12, 2012 [1 favorite]

There are two problems

a) most digital recording devices record at 44.1 kHz (and 16bit) so they will not actually record at above frequencies of about 22kHz So you need to get a recorder that can record at higher sampling frequencies. such as 88.2kHz or 96kHz - these do exist.

b) the frequency range over which microphones actually function may be limited. So you need to find a microphone with a high frequency range.

After making a recording you could then load it into a Audio Editor program and slow down the playback to say halfspeed - which would then shift any data within the 22kHz - 44kHz into the hearing range.

If you used Tape you might avoid this but only if the frequency response of the Tape, Microphone and Tape Recorder are also very high. Then playback the tape at Half-Speed.
posted by mary8nne at 10:56 AM on November 12, 2012

I've looked into this and have had experiences similar to mary8nne. 99.9999% of audio recording is done in the human hearing range, so all of the equipment out there is optimized for that.

In short you need to buy some (very expensive) lab equipment or get heavily into some DIY. The Wildlife Sound Recording Society runs through some of the challenges to overcome these limitations on this page. A commercial microphone to record higher frequencies runs in the $3000 range. There are companies that sell a full ultrasonic wildlife recording rig, but they start around a grand. If you aren't afraid of a soldering iron and know your way around a schematic you can build your own for a small fraction of that. (You could probably find an electrical engineering student or member of a local hackerspace to build it for you as well.)
posted by Ookseer at 12:21 PM on November 12, 2012

Tape recorder, expansion: Try to get hold of an old Uher Report portable tape recorder someplace and some old tapes. These nifty machines have four steps, always half as fast (or twice) as the previous. Endless fun.

[I once recorded a budgie with one of these and stepped it all the way down. I got what sounded like a yodel-tenor having stomach problems. I then recorded my own imitation of the melody on low speed, stepped it up all the way again and played it back for the bird. The poor thing went completely bananas; "Where's that other BIRD!!!" For some reason I never tried to record my rabbits. Missed chance...]
posted by Namlit at 12:54 PM on November 12, 2012

Comment from my fiancee:

Rabbit vocalisation is within the hearing range of a human

So there is no point buying an expensive microphone. My guess is that the rabbits hear something that is not audible to humans. That would be something in the ultrasound range:

Rabbits hear up to 42kHz, humans 20kHz.

Maybe there's a mouse in the flat?
posted by TheophileEscargot at 11:48 AM on November 14, 2012

Fascinating. So you suggest that they can hear things we can't hear, but cannot say things we can't hear? A mouse is a definite possibility.
posted by epanalepsis at 1:27 PM on November 17, 2012