Ultrasonic pest repellers show, at best, mixed results, according to the International Association of Certified Home Inspectors. While some anecdotal evidence claims effectiveness, scientific testing does not show long-term results. For people who wish to avoid using chemical pesticides, live traps or cats give better results.
While ultrasonic products may appear to work initially, rodents become habituated to the sound, quickly figuring out that the noise is not a threat and resuming their normal behavior. Ultrasonic sound waves also have a short range and are blocked by walls or furniture, making it impossible for these repellents to reach pests within walls.
In 2001, the Federal Trade Commission warned ultrasonic repellent manufacturers that their advertising must eliminate false claims and show established scientific proof. In response, companies such as Victor provide lab and field test data on the product webpage. More recently, Riddex has been the subject of two class-action lawsuits alleging that the products did not work as advertised. The lawsuits were combined and settled, and Riddex still produces the product.
The Victor field tests show effectiveness for small populations up to six weeks, although the website shows tests not credited to sources. Victor recommends using the devices to herd rodents to areas with traps and rodenticides, as the repellents themselves do not control infestations. Victor also cautions that walls and furniture block the sound waves, so one device will not work by itself.