When background music is added to a TV show or movie for dramatic effect, but it ends up drowning out the dialogue to the point at which a viewer can't even hear what people are saying. It is a stylistic choice based on the assumption that most viewers are primitive creatures whose attentions will more likely to be captivated by primitive noise than by words.
Although "ear-jamming" occurs in all types of auditory media (radio, TV shows, and movies), it most commonly occurs in documentary-style TV shows and movies.
It usually leads to a situation where viewers are constantly modulating the volume of their TVs as they watch a program in order to either: (1) mitigate the assaultive music or turning the volume down
(2) or to hear the now-relatively-quieter underlying dialogue turning the volume up
When the background music comes on especially suddenly, it is also know as a "music assault".