The sound has a reverb like a blown speaker..

Check the audio output from the headphone socket at the back of the TV and listen if it sounds distorted as well or connect a receiver via the audio out connections (remember to change the audio settings in the TV to “TV speaker off”) and check.

If it still sounds distorted then there is a problem with the audio amp or the audio processor in the TV.

If not then most likely it is the TV speaker.