[chuknospam]

The aural carrier (audio) & visual carrier (video) are generated separately then combined (in a combiner of all things) to be broadcast. If the visual transmitter, exciter or intermediate amp takes a hit or has a failure then, you can have audio without video or vice versa. If they hear a loud noice in the control room, it was likely a filter capacitor or transformer exploding. Just a speculation based on experience.

[chaosagent]

Ever been around the xmtr HV cage when some idiot opens the cage while we're on the air and the shorting bar arc-welds itself across the HV, and then caps and rectifiers start exploding like M-80s?

Talk about your bright light!

[RightWhale]

If they hear a loud noice in the control room

It can be an impressive sound, usually because it is unexpected. Somewhat short of a nuke, however.