This DIY Bat Detector Picks Up Ultrasonic Chirps in Real-Time
The device is made up of a MEMs microphone, PCB board and lithium-ion battery, all housed inside a 3D-printed enclosure.
Unless you have an ultrasonic device or you’re Batman, the ultrasonic sounds bats emit for echolocation can’t be detected by the human ear. You need a special microphone to capture these high-frequency sounds and convert them into a sound within the human audio frequency. This is typically done using a bat detector. Instead of traversing Amazon for hours, one hobbyist named Marcel decided to make their own heterodyne detector, which captures a bat’s sound in real-time.
The detector is made up of a Knowles SPU0410LR5H MEMS microphone, which has a flat frequency response up to 80kHz — ideal for this use. This small mic is soldered on to a PCB equipped with a dual op amp. Marcel also built a frequency mixer and an analog switch for the device.
A lithium-ion battery powers the detector with a supply between 3V and 4V. The circuit board, microphone PCB, and knobs for volume and frequency are housed in a 3D-printed enclosure. Once a plug is inserted into the headphone jack, the power is automatically turned on.
So, what are the results? In addition, the detector, you need a recording app that lets you simultaneously record and playback to listen to bats in real-time. Marcel recommends the RecForge II, but any app that allows you to playback and record at the same time should work. With this setup, Marcel was able to hear and record a local bat’s ultrasonic birdlike chirping.
If you want to create your own heterodyne recorder, see Marcel’s detailed process here.