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How is it that they receive and transmit ultrasonic frequencies with a computer sound card? Is there not a low-pass filter at around 22KHz on inputs and outputs
by rafavega 13y ago
How is it that they receive and transmit ultrasonic frequencies with a computer sound card? Is there not a low-pass filter at around 22KHz on inputs and outputs of all sound cards?
- deutronium 13y agoI was able to transmit at up to around 23kHz which you may be able to make out the spike on the FFT graph on the video I made for some previous work: http://www.youtube.com/watch?v=H0DKRl8XIcU http://www.youtube.com/watch?v=H0DKRl8XIcU To get up to 23kHz I used a sample rate of 48kHz.
- nitrogen 13y agoThe built-in audio on most PCs these days supports 96kHz or even 192kHz sample rates.
- whoopdedo 13y agoThe DAC may sample at that resolution, but it's another matter if the driver will pass an ultrasonic frequency. Looking at a few datasheets from various manufacturers, I don't see any mention of bandpass filters. So either they don't have them or they don't think it's worth mentioning.
- ackydoodles 13y agoNo.
- lutusp 13y ago> Is there not a low-pass filter at around 22KHz on inputs and outputs of all sound cards? It's not a low-pass filter per se, the limit is imposed by the Nyquist–Shannon sampling theorem (http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samplin...), which essentially limits the frequency spectrum to 1/2 the clock rate. Good-quality audio from a sound card is clocked at 44 KHz, which means the audio range extends only to 22 KHz. But you can clock a modern sound card at a rate much faster than 44 KHz, so the above might be only the normal limit, not the extreme.