I don’t know how flies hear sounds or waves or whatever, but I do know that while I was using this app, a fly landed on me. So there’s that. Decide for yourself, but 1/1 it’s a hard no.
Ultrasonic Pest Repeller is an application that works by generating Ultrasonic waves (out of audible range) that most pest find repugnant. This will prevent you from getting bitten by mosquitos and other insects. The pitch of the sound is so high that most humans will not hear anything.