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| What's the best way to receive ultrasonic signals? |
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| Ben321:
I was curious about what kinds of ultrasonic signals are just in the environment around me. I've heard that bats for example can have emissions well above human hearing, and some even as high as 100kHz (higher than the highest frequency that can be detected with a 192kHz soundcard, which has a nyquist frequency of 96kHz). So I need a way to easily get ultrasonic signals into my PC. The best commercially available sound cards (which aren't pieces of dedicated science equipment) are 192kHz sample rate (which has a nyquist limit of 96kHz), but I'd like to go a bit higher than this (with a nyquist frequency of at least 100kHz). Any suggestions? Of course, I also need a microphone that can sense ultrasound. Typically microphones are designed to be most sensitive between 20Hz and 20kHz, as this is the range of human hearing. A typical microphone won't work very well even at the highest frequencies usable on a 48kHz sound card (which has a nyquist limit of 24kHz), as 24kHz is above 20kHz. So a typical microphone won't be a usable untrasound sensor. There are dedicated ultrasound transducers, which are usually sold as a pair, for transmit and receive. However, these are usually designed for one specific wavelength (like 35kHz), and don't perform well at any other frequency (either higher or lower). Are there any wideband ultrasound sensors (with a usable range maybe between 20kHz and 100kHz) out there that don't cost thousands of dollars (like it would cost for a dedicated medical/scientific device)? |
| Brumby:
Try something as simple as a Google search for "ultrasonic microphone". I did - and this was the first reference: Low-cost ultrasonic recording - Wildlife Sound Recording Society http://www.wildlife-sound.org/equipment/technote/micdesigns/ultrasonic.html "A couple of years ago, a manufacturer of bat detectors started using cheap electret microphones in some budget detectors, presumably after finding out that some capsules had a useful response up to about 60kHz. One of these capsules is the Panasonic WM61A which features in the WSRS low cost microphone design article. If you have constructed that, you are already there - go in search of bats!" There's a place to start. |
| Ben321:
--- Quote from: Brumby on May 20, 2017, 02:31:47 am ---Try something as simple as a Google search for "ultrasonic microphone". I did - and this was the first reference: Low-cost ultrasonic recording - Wildlife Sound Recording Society http://www.wildlife-sound.org/equipment/technote/micdesigns/ultrasonic.html "A couple of years ago, a manufacturer of bat detectors started using cheap electret microphones in some budget detectors, presumably after finding out that some capsules had a useful response up to about 60kHz. One of these capsules is the Panasonic WM61A which features in the WSRS low cost microphone design article. If you have constructed that, you are already there - go in search of bats!" There's a place to start. --- End quote --- What about the soundcard part of my question? Are there any good soundcards that hobbyists tend to use for receiving ultrasonic signals? Are there any that have sampling rates over 192kHz, so as to allow the nyquist frequency to be above 96kHz? I'd hope to get a sound card with a nyquist frequency of at least 100kHz. |
| BrianHG:
$$$ for anything above 192k unless maybe some instrumentation devices. Otherwise, for sound, go here: https://mytekdigital.com/brooklyn-adc/ |
| NiHaoMike:
If you add a quadrature mixer, you double the available bandwidth and shift it up towards a frequency range that is more useful to you. |
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