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This question already has an answer here:

Is there a way to increase frequency of an audio, for example (OK GOOGLE) recording of someone to inaudible range without change the way how it sounds? i.e >20000 KHz or <20 Hz. A simple increase in frequency is resulting in increase of pitch.

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marked as duplicate by A_A, lennon310, hotpaw2, Matt L., MBaz Jul 23 '18 at 15:48

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    $\begingroup$ I don't understand the question. If the frequency is inaudible then it sounds like silence, not like the original recording. $\endgroup$ – Olli Niemitalo Jul 20 '18 at 13:00
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    $\begingroup$ But making it inaudible alters the way it sounds... $\endgroup$ – endolith Jul 20 '18 at 14:12
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if you are old enough to remember what was happening when a casette player (or even previously viynl LP) playback speed was changing, then you could understand that when the frequency of a sound changes, its pitch will also be changing accordingly. The effect can be simulated by adjusting the playback sampling rate of audio clips in OCTAVE/MATLAB.

From another perspective, if you relocate the spectrum of an audio signal (aka modulate it) into another portion, that might again change the pitch as well as distorting the harmonicity and timber. Yet when demodulated back into its original band, you will retain it perfectly back.

If you relocate it into ultrasound region, then of course you cannot hear it without demodulation back into hearable baseband.

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