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Ultrasonic transducers emit sound at a frequency greater that 20 KHz. What are the ways the frequency of sound emitted by such a transducer can be verified?

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  • $\begingroup$ Common microphones sample rates are 44.1 kHz and 48 kHz, but I also believe 88.2 kHz and 96 kHz can be found as well. So I do not know what is the limit at which they can record, but by measuring at different frequencies you might be able to determine the actual frequency if it is above the Nyquist frequency due to aliasing. $\endgroup$ – fibonatic Sep 6 '16 at 21:59
  • $\begingroup$ are common microphones sensitive to ultrasound? also, if frequency of sound output is more than the sampling frequency of the microphone, will this method work? $\endgroup$ – akm Sep 7 '16 at 0:18
  • $\begingroup$ Microphone designs have different characteristics. Some have very sharp roll off at high frequencies, others don't. Their specs should give a graph showing frequency response. But in my experience, all would need significantly greater amplification (and high pass filtering) $\endgroup$ – CL22 Sep 7 '16 at 16:40
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    $\begingroup$ With an ultrasonic microphone, of course! $\endgroup$ – Carl Witthoft Sep 8 '16 at 15:03
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If you're talking about a "bare" transducer (i.e., not a module with its own driver), you can just hook it up to an oscilloscope, hit it with a narrow pulse of voltage, and look for the decaying waveform of its self-resonance. Measure the frequency of that waveform.

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  • $\begingroup$ while the answer is correct. practically speaking, it may take huge number of iterations. imagine iterating 20k times for a 40k transducer! also, oscilloscope are costly devices, typically not owned by individuals, making it very costly approach as well. $\endgroup$ – akm Sep 7 '16 at 0:15
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    $\begingroup$ I don't know what rock you've been hiding under for the past 5-10 years, but scopes with the capabilities required for this task are readily available and dirt cheap. Even brand new low-end USB-based scopes (that use your computer for their user interface) are a few tens of dollars at the most. $\endgroup$ – Dave Tweed Sep 7 '16 at 0:27
  • $\begingroup$ Could you please provide link to cheap oscilloscopes? $\endgroup$ – akm Sep 7 '16 at 0:47
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    $\begingroup$ @AmitMaurya ... Ebay, search for "usb oscilloscope". $\endgroup$ – CL22 Sep 7 '16 at 16:46
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    $\begingroup$ ... or Sparkfun, or Alibaba ... or you can get creative: many microprocessor evaluation boards (which can be had for a song) have a demo program that turns them into a low-end scope in order to demonstrate their analog and USB capabilities. $\endgroup$ – Dave Tweed Sep 7 '16 at 16:58

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