Bats breathe in and out pushing air past their vocal chords every time they flap their wings. Their call is a series of ultrasonic pulses and they listen to the echoes of these reflected from flying insects to locate their prey. They mostly emerge from their roosts just after sunset.
To listen to the bat calls we have converted them to 1/10 the original ultrasonic frequency to bring them into the range adults can hear (children can hear bat calls in the 20kHz region, adults might hear sounds below 8kHz.) The top chart shows these frequencies while the bottom chart shows the sound intensity, both charts with the horizontal time scale covering the 1 min 3secs of the recording.
The sonogram above charts the previous audio starting with a bat call at 44-50kHz (multiply the recorded frequency by 10 remember) with some very rapid high intensity feeding buzzes when it is catching an insect, it could well have caught 10 insects in this time. Towards the end there is a lower frequency buzz at 20-24kHz.
The bat is a pipistelle from the call frequency in the table, the lower frequency is thought to be a social call to another bat.
| Bat | Frequency(kHz) | Pulse Duration(ms) | Pulse Interval(ms) |
|---|---|---|---|
| Common Pipistrelle | 41-50 | 2.5-7.5 | 90-165 |
| Noctule | 17-24 | 4-20 | 140-230 |
| Daubentons | 35-39 | 2-6 | 28-75 |
| Brown long-eared | 20-26 | 0.5-3 | 50 |