Satisfactory... I guess

I have used this several times. I live in a very old wooden building in Central Tokyo and often hear noises above that I believe are rats. Whenever I left this app running I noticed those noises disappear. Im not sure whether the rats are actually gone or the apps noise is disguising the rats footsteps.
Also, I use my old iPhone to run the app. I activate in the morning but when I get home late afternoon the app has crashed.

Craig00:00:00 about Ultrasonic Pest Control, v3.0