Thanks for posting in the Apple Support Communities. If I understand your post, you're having some issues with the audio from the built-in speakers on your MacBook Pro. More specifically, the audio seems muffled, and generally it's difficult to hear. I'm happy to help!
First, make sure there isn't anything blocking your speakers, like a case you have on your computer, or any debris. As long as that's clear, I would recommend first restarting your Mac: How to turn your Mac on or off - Apple Support. If your speakers still are giving you some trouble, the next thing I would recommend would be to reset the computer's NVRAM, which controls some of your volume settings: How to reset NVRAM on your Mac - Apple Support.