Originally Posted by JSanders
Welcome to the Forum.
It sounds like the internal speaker is having problems. Have you pulled the battery (while powered on) and let the device reboot?
Plug the earphone in and out rapidly a few times, sounds like the internal plug is dusty and holding contact when the plug is removed. Blow it out with canned air or a compressor and give it a try.
Use caution and hold canned air 100% upright do not tip it and spray liquid condensed in the can into the plug.