Anti-Mosquito produces sound in the range of 16000hz to 20000hz that is beyond the audible range of humans.... but mosquitos are other harmful insects can hear it.
It keeps generating sounds while the device is locked or in sleep mode.
Overall I really liked this app, the only downside is for the animals, don’t leave your the app on with the maximum volume and your dog or cat right next to it; make them go in an other room. Overall, this is a really awesome app! I’ll give it a 4/5.