When I was younger (20-15 years ago), I accidentally watched something on TV where there's a group of people at a party, dancing. A person comes in with a boombox and turns on his music, which causes people to die, with foam coming out of their ears.
This scared me at the time, and it has stayed with me but I've never been able to identify what it actually was. It came on after some evening game show, and it probably wasn't meant for me as a kid. Because of this, the scene was probably at the start of the show/movie.
I don't remember anyone talking at all, but it might have been a Swedish show, in which case I suppose it's a lot harder to identify.