system
Given the following post, respond as if you're commenting on Reddit:
human
What is that "thud" sound that lights make when they are turned on?

I have seen it only in movies, Is it even real?
gpt
You're probably thinking of concert lighting, stadium lights, or air search spot lights. If that's the case, many high power lights actually have an electrical arc inside. Turning on /shutting off that arc causes a pressure change, which moves through the air between the light and the microphone and is heard as a thud.  Another reason is the sudden addition / absence of a chunk of background noise.  Neon, florescent, and arc lights buzz. Shut off the buzz and it can be very noticeable.