Silent wall speaker

Am trying for the first time to run a business, after all the years I've been playing TS2 since its launch. It is a home based one rather than a bought community lot. I put a wall speaker in the customer area in the hope the music will improve the environment. Problem is, nothing is coming out of the speaker. I know from the OFB book that some sorts of business activities won't work in a home based one, but saw nothing about speakers.

Anyone have any ideas? Thanks in advance!