What are the facts regarding Apps which claim to repel Mosquitos/insects?

They claim that a certain level of soundwave repels them. It’s supposed to be out of human hearing range yet some people claim it gives them headaches.

The reviews are all over the map so that’s not much help. Could the positive reviews just be due to placebo effect?

I’m just curious if there’s any science behind their claims?

Have you used any of them? If you found one that worked, which one was it?

BTW: All the ones I’ve looked at are free so I guess profit motive isn’t a factor here.