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I was watching this video when I came upon this question: wether it be high frequency or low frequency, sound waves are made of high pressure and low pressure areas (they are waves, after all).

I mean: they are not equal at every point.

However, it doesn't seem like we can distinct high pressure from low pressure areas in a sound wave. Is that correct? For example, when the sound from the linked video starts, we only hear a continuous sound (it doesn't seem to stop or be wavering at any point, even though the frequency changes).

Why is that? My guess is our ears or brains somehow translate this information into something continuous, but I'm not sure.

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Between around 12 and 12000 Hz our perception of sound is roughly speaking in time Fourier transform. We perceive the spectrum of the wave and not the wave itself.

This is the reason why we recognise a melody even if it is played in the wrong octave, or why we find the fundamental harmonic even if it is not present in the sound due to filters...

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  • $\begingroup$ Thank you! Do you have an intuitive / layman description as to what is the Fourier transform you mention in this case? $\endgroup$ – user137288 Jan 3 at 21:03
  • $\begingroup$ Every periodic wave is a discrete superposition of simple harmonic oscillations with precise frequencies and intensities. The Fourier transform (more precisely the Fourier series) contains these frequencies with their intensities. Our brain elaborates the sounds at this level. $\endgroup$ – Valter Moretti Jan 3 at 21:06
  • $\begingroup$ A sound is a sound if the frequencies are integer multiples of a given basic frequency called fundamental. That is the name of the sound. $\endgroup$ – Valter Moretti Jan 3 at 21:08

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