Audio needs good amplifiers at the receiving end to make it any use. Most, or I'd go with "all", surveillance cameras with audio are crap, to put it bluntly, at giving decent audio, that's unless they are connected to an amplifier with good bass tone and treble frequency control. If going for audio facility on the camera, then try to choose one with a compressor microphone.
Would you believe the best camera with audio I've ever used, and still continue to use where needed, is this one:
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it's worth shopping around for a while before committing yourself I find.