The keyboard on the new MacBook Air 13 M4 is rattling

The issue does not sound normal to me, a very long time Mac user. Your description of the problem as "crunchy" is interesting.

At the very least you might visit a retailer that has Mac laptops on display and compare the keyboards of any of those display models with your experience.

Otherwise, if you bought the Mac directly from Apple, then you have fourteen days to return the computer for refund or exchange. Returns & Refunds - Shopping Help - Apple

Same issue here! MacBook Air 13" M4 512GB 24GB in Sky Blue, keyboard rattles and resonates when playing sounds... It happens in movies, music, voice notes and even system sounds between half and full volume. I went to the Apple store and compared my Mac with their display 13" M4 Air (256GB 16GB Sky Blue) which didn't present the same rattling.

I returned the laptop and am currently waiting for a replacement unit to arrive. I'll let you know if it has the same issue.

The keyboard being "crunchy", I also noticed it, on certain keys is likely Apple using different key mechanisms between the alphabetic and other keys (like the command key), this is just speculation on my part but it is a pretty common on budget laptops, it's pretty disappointing to see on a starting at $1000 laptop (once again, this is speculation).

I'd love to know if anyone else has experienced these issues.