Earpiece and Top Speaker not Working

Hello,

One day all of a sudden my earpiece and top speaker for Nexus 6P stopped working.

It never had any issue till then, nothing minor either. It was working perfectly fine till the day before.

Therefore I'm a bit skeptical if it's indeed a hardware issue and if I should replace the earpiece/top speaker.

Do you have any suggestions on what it could be or how I can find out the exact cause?

Regards,

Justine.