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Can I record a sound frequency I can't hear and play it back so I can hear it?

If yes, How?

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2 Answers

up vote 7 down vote accepted

This is actually really straightforward given one caveat:

  • Your recording hardware and software needs to have a frequency response which includes the range you want (either very low or very high)

Almost all professional recording software will let you frequency shift - either directly, or by speeding up or slowing the playback of the waveform. Even free software like Audacity will do this.

If you are recording ultrasonic frequencies, just slow your waveform playback down; and do the opposite for subsonics.

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Wow, as someone new to audio recording I didn't know you could slow down playback to hear ultrasonic frequencies. Love learning new thing +1 –  Phill Pafford Aug 4 '11 at 14:00
    
Would there be any other ways to record ultrasonic frequencies and playback (without slowing down) to hear the sound? I guess this is a bonus question? –  Phill Pafford Aug 4 '11 at 14:02
    
You could use frequency shift technology which is available in Cubase, Sonar and various other tools. Those ones won't necessarily give you very good quality as they are targeted at the audible frequency range, but that may not be important, depending on your needs. –  Rory Alsop Aug 4 '11 at 14:29
    
you can even run audio divider circuits - commercial ones like octave dividers are already used to make guitars sound like basses, for example. –  Rory Alsop Aug 4 '11 at 14:38
    
@PhillPaford: You can also use modulation to move ultrasound into the audible band, but it won't keep the same harmonic shape. –  endolith Oct 10 '12 at 18:33
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To expand on Dr Mayhem's great answer:

It is not possible to hear a frequency that you cannot hear.

It is possible can transform a frequency that is too high or low to hear into one that you can, and you do that by shifting the recording's frequency as Dr Mayhem describes.

You won't be hearing the original frequency, but you'd be hearing a sound at the transformed frequency that has the same characteristics as the original, which I believe is what you're looking for.

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