My ipad 2 speaker has stopped working

Happened suddenly yesterday when I was on a Facetime call. Works OK through headphones. It's nothing to do with the volume or mute buttons, and I have tried a hard reset more than once. Worryingly, I discovered that a gentle tap on the back of the ipad brought the sound back temporarily - but now it seems to have gone altogether. 😟

Any solutions based on your experience would be welcome. I have a bad feeling about this ...