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I’m trying to understand how an audio signal is represented with electrical signals and modulated. I and have questions which follow. Wikipedia says

An audio signal is a representation of sound, typically using ... a changing level of electrical voltage for analog signals

The audio frequencies are 20 to 20,000 Hz. More then one frequency can be present with different amplitudes.

It’s my understanding this signal can be modulated to an AM carrier (mixing) and shifted to sidebands. Why is the bandwidth of the sidebands in the picture below so large? The frequency of the sideband signal should be constant and only amplitude changes.

For FM I think I understand the side band width because the modulated FM signal is changing frequency in the sideband bandwidth range, which represents the audio signal.

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Nick
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    as already pointed out in the answers and comments to your other questions, bandwidth **is** the result of modulating the amplitude. That's the math of what a spectrum is. Again, this has already been explained by Math keeps me busy, Justme, and Peter Bennett. No real need to repeat it a fourth time! – Marcus Müller May 30 '22 at 17:20
  • @MarcusMüller I know this is closed, but have a question. If the AM signal is modulating it's amplitude, why is the spectrum (range of frequencies) so large? I expect the AM signal is constant frequency with variable amplitude. Maybe I'm missing some math you can point me towards to understand this phenomenon? Thanks – Nick Nov 11 '22 at 06:16
  • That's already been answered. It's the audio spectrum. The reason this question is closed really is that it's already been answered! – Marcus Müller Nov 11 '22 at 09:00

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