Calibrating your bat detectorSome ways to generate ultrasonic tones and noises:
- PAL 50 Hz TV's generate ultrasonic tones at the horizontal line frequency of 15625 Hz and multiples of that (31250 Hz, 45875 Hz, 62500 Hz etc.).
- Many digital watches use a 32768 Hz crystal, that you can hear if you hold the watch really close to the bat detector microphone.
- Rubbing your fingers generates ultrasonic noise up to about 60 kHz.
- Handling a wrinkly plastic lunchbag also produces lots of broadband ultrasonic noise.
- Rattling a bunch of keys produces metallic sounds on a heterodyne bat detector.
- USonic, a freeware MS-DOS based utility for generating ultrasonic tones using the PC's built-in speaker. Written bij Joost Ruijsch.
- My own Calibration program (screenshot), a utility for generating ultrasonic tones on a Handspring Visor (Palm clone).
This page was last updated July 28th, 2005