That's the impression you get from the sound, that you call 'high' or 'low', determined by the FREQUENCY of the wave.
The pitch of a sound wave is determined by its frequency, measured in Hertz (Hz). Higher frequencies correspond to higher pitches, while lower frequencies correspond to lower pitches. For example, a bird's chirp has a high pitch due to its high frequency, whereas a lion's roar has a low pitch due to its low frequency.
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