I just read the ticket for the sound system.

The initial order was for them to remove the rear panels, maybe seats? to gain access to the rear sub speakers to add padding. On inspection, the cones were separating from the voice coils causing a buzz on both sides. Both speakers were replaced and there is a note that then new speakers had additional padding so none needed to be added.

I'm paraphrasing a little but that was the substance of the ticket. It's much better.