On paper, Boeing’s High Energy Laser Mobile Demonstrator (HEL MD) is decidedly less fun than the lasers you see in the movies. They're invisible, silent, and they don't always blow things up on contact. The undetectable beam is set to be used as a military device that will shoot down aerial targets like enemy rockets and drones.
The HEL MD uses a 10-kW fibre laser to pick off its targets with extreme precision. There isn't always an explosion so, as a result, engineers have a problem figuring out if the HEL MD is even firing. The obvious answer to this problem is to take a page from the (much more audibly dramatic) lasers in science fiction.
“The engagements happen quickly, and unless you’re staring at a screen 24–7 you’ll never see them,” engineer Stephanie Blount told Nature. “So we’ve built sound in for whenever we fire the laser. We plan on taking advantage of lots of Star Trek and Star Wars sound bites.”
The reason to add these sounds is for those using it, and not as a warning.