Ultrasound
Definition: According to Wikipidia, ultrasound is a form of cyclic sound pressure with a frequency greater than the upper limit of human hearing, this limit being approximately 20 kilohertz (20,000 hertz).
Ultrasound and ultrasonics are frequently touted as effective tools to evict wildlife from areas and structures. While the concept sounds promising, the reality is rather dissapointing. There are several reasons why ultrasound doesn't fulfill customer expectations.
First, many animals cannot hear in the ultrasonic range. So since the ultrasound must be heard to be effective, any sound that cannot be heard cannot become a nuisance to drive an animal from the location.
Second, even those animals that are able to hear in the ultrasonic range (e.g. bats), the sound wave of ultrasound often lacks the intensity needed to drive the animal away. For instance, bats roosting on an attic rafter can easily crawl down the side of the wall and experience signficantly reduced sound. Remember, animals, once they become habituated to a site, are unwilling to abandon that location without some resistance. The reason is simple, finding a suitable home is difficult in nature. Once they have one, animals resist giving it up.
Third, there is always the problem of knowing for sure the device is actually emitting sound. Since humans can't hear the sound, how do you know the device is still working properly?
Finally, researchers have found that ultrasound simply didn't meet expectations,particularly with rodents. I have provided some resources below.
Ultrasonic and Subsonic Devices Washington State University. Sprock, C.M., W.E. Howard, and F.C Jacob. 1967. Sound as a deterrent to rats and mice. J. Wildl. Manage. 33194)724-736. Howard, W.E., and R.E. Marsh. 1982. Ultrasonics and electromagnetic control of rodents. Third Intern. Theriological Congress, 15-20 August 1982, Helsinki, abstract. Howard, W.E., and R.E. Marsh.1985. Ultrasonics and electromagnetic control of rodents. Acta Zool. Fennica 173:187-189. EPA funded our electromagnetic study and we worked with EPA to help the Federal Trade Commission try to ban ultrasonics. I think we demonstrated that the success of a rodent control program with ultrasonics was just as successful if the units were not turned on.
If none of those findings convince you, even Animal Rights Groups don't recommend ultrasonic devices as noted in The Humane Society of the United States book, Wild Neighbors by John Hadidian.
