I just had the sound problem when I got off work this morning. In researching it, I see that people have a different mix of sound problems. Here's what mine were. I could hear my ringtone and other tones (text, alert, alarm, etc). I couldn't hear any music. I couldn't hear the other person on a phone call. I couldn't hear system sounds like the camera shutter and touch tones. Pinching the area by the speaker did nothing. I saw this post about plugging in headphones and removing them. When I plugged in headphones, I could hear everything that I couldn't before. But only through the headphones. When I unplugged them, the problem remained. Just for the heck of it, I sprayed some Dust Off into the headphone jack. PRESTO! I have sound now.
I pretty much never use my headphone jack. I connect my Maxx to my car stereo all the time, but I use the car dock with the USB jack that carries the sound to the aux jack in my stereo, rather than the headphone jack on the phone. I'm wondering if sticking a little piece of rubber in the jack might prevent the problem. I'm thinking it just gets contaminated with dust.