Need help with my Television audio
 

thx for clicking

earlier today i was playing my Wii and everything was cool. i turned off the Wii and TV. several hours later i turn on the TV to watch leno but the sound is muffled and dampened like i am underwater or pillows are stacked in front of the speakers. bass comes through but not the higher ends. turning up the volume does nothing but vibrate my house. lol. the TV is 4yrs old. what the heck is the problem?

changing audio ports does nothing.
changing devices that output sound (Wii, dvd) does nothing.
tv settings were not changed and are set to default.