It has been a number of years since the initial post so perhaps technology has improved. All I can say is about 5 months ago I installed an ultrasonic device in my big old barn. Occasionally I see some rodent activity but for the most part the large and I mean large rat population has vacated the premise. Used to be after feeding the chickens in about 5-10 minutes the feeders would be completely covered with rats....serious problem. Feeders were emptied immediately. Now rats are gone !! I can go out any time of day and there will be feed left in the feeders both in the chicken pen and my outdoor peafowl feeders. However that being said egg production is down (my chickens are all past their prime) and I am still testing to see if the ultrasonic device is to blame. It is still winter so it may be just the normal daylight production issue. Time will tell. For me the device worked like a charm and my feed bill has been greatly reduced.