M1 Max MacBook Pro: Left speaker suddenly sounds like a frog

I SWEAR it wasn't doing this earlier! I'm autistic, I'd have definitely noticed! It's been rebooted, but it's not made any difference! It's definitely not been dropped. Just used on my lap/bed as normal. It's under AppleCare, but I can't get to an Apple Store. Any ideas on what could be causing it, and how to mitigate/fix it...?

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