I was out in the desert a few weeks ago and was recording some insects and I saw a bat flying around my recorder. So I set the recorder to record up to 96khz frequency even though my microphones were only rated to 20Khz (human top audible frequency....when you are young!). I figured I would get nothing but when I looked at the spectrogram I saw this (this is just a short section) -



Those black "slashes" at 40-50Khz are the bat calling. I was surprised to capture it since they are ultrasonic, well outside the range of human hearing and the microphones supposed limits. Sure, you can buy ultrasonic microphones that are designed to capture bat sounds but this was a cheap pair of regular microphones (Studio Projects C4 cardiods).
The five dark lines at just below 5khz are a cricket calling.

When I slowed the call down 90%, it gets into the range that you can hear it swoop down towards the microphone and away again.
Remember, this is slowed down 90%. There are actually ~7 chips per second on the real recording at normal speed.



At another spot in the recording, it rapidly accelerates its call (maybe to home in on an insect?) -



Nothing earth shattering. I just thought it was cool to have caught that with relatively cheap, non-specialized gear.

Chris, that is awesome. I have a few friends who do a bit of bat work and I seem to remember that certain species of bats have parts of their echolocation that is right at the point certain people can almost hear. They also are more than capable of making audible (to us) noises. Curtis Hart may be able to expound more on this as I know he has worked as a bat tech.

All that I've done with bat calls is set out Anabat Detectors and download the data. I've never analyzed the data. Bats do make audible sounds. Big Browns and Hoarys in particular are pretty loud of the ones I've handled.


Curtis

It's amazing to see sounds on a spectrogram! This is cool! Thanks for sharing!