Gongs during games

I have noticed many times during televised football games a sporadic sounding of what sounds like a gong announcing the hour, but it seems to be randomly spaced. Also, I have heard the sound during games at the Michigan Stadium. And it is not Burton Tower or a nearby church. Has anyone else noticed this phenomenon? Or, better yet, has anyone an explanation why this happens. It seems often during the games (college, but not pros).

'too

Those are the gongs from the beginning of the song "Hells Bells" on the PA.

Usually played to get the crowd going that's why they're random.

You're showing your age! lol

It's AC/DC

Some traditionalists would say it's stupid.