You are hearing Described Video (DV), a service that helps people who are blind or have low vision to enjoy the program.
Your TV or set-top box will have an audio or language setting that allows you to select standard audio or DV. If you have accidentally turned on a selection labelled as SAP, Secondary Audio Program, Described Video, Descriptive Video, Audio Description, or something similar, you’ll hear DV on the programs that feature it.
To stop it, turn the feature off and/or select standard audio or stereo in your audio settings. Please consult your owner’s manual for details.