Problem: field mouse running in the attics, and recently, one timely and consistent racoon came down the trees on to the roof and ripped a small gap on the side allowing the said racoon (and more mouse) to get in and out the attic. We have several fruit trees in the yard, so I believe these small animals are here for the buffet. Drove me insane around 1-2am. Got the Victor M793 after reading Amazon reviews, ordered it around 1:45AM and received it by 5PM, plugged it in, and started to work slowly night by night. The first and second night, yep like clockwork, I would hear the racoon coming down the tree, running across my roof, same route to the place where he/she clawed a gap. BUT- with the repellant on, the racoon would not enter. The mouse problem also improved because I do not hear little footsteps running inside of my ceiling anymore.You'll have to put it in the right place allowing the sonic wave to travel, place it somewhere central and point it to the general direction where you've been hearing noise the most. When you turn it on, it has a very faint buzzing sound, my dog doesn't seem to be affected by it. The M793 also has a pulsating red light. Not police siren red, but a dim kind of red. I guess small critters will find it annoying, even blinding?!??We live in the suburbs of LA. We have the usual urban small animals running through our yard grabbing fruits and finding shelter- possums, squirrels, rats, mouse, stray cats. The worst on the list are skunks and racoons. I have "mastered" skunk- Havahart cage and a generous wad of peanut butter- done! Racoons come down from the trees on to the roof, so they're a bit more tricky and sneaky.I have this machine on every night since purchase on 5/29/2015 and today is 6/30/2015. Haven't heard any noise in my attic or inside my roof since the purchase, so.... highly recommended.