Hobbies And Interests
Ultrasonic
Generally, the electronic pest repellents emit an ultrasonic sound that is inaudible to humans but distressful to rodents and pests; however, the sound is not supposed to be harmful to household pets such as dogs or even gerbils. Some researchers such as Leonard Askham at Washington State University doubt that a noise could possibly be effective at repelling mice but not harmful to gerbils, as many manufacturers claim. This leads to doubt that the noise is effective at all.
Habituation
One major problem with the effectiveness of ultrasound is habituation. Habituation occurs when a rodent realizes that the alarming sound is not actually harmful, and become accustomed to its presence. While they may initially flee, they will return to their productive feeding or nesting ground after becoming used to the noise. This short-term effectiveness explains the continuing popularity of electronic pest repellents, but the frequent return of the pests explains the debate over whether they actually work.
Range
Another issue is the relatively short range of ultrasonic sounds; generally speaking, they diminish considerably after 15 feet and their energy is practically gone by 30 feet. A number of devices would therefore be needed to cover an entire house or yard. Additionally, ultrasound is blocked by objects such as furniture, giving pests a convenient shield from the unpleasant effects of the noise. Ultrasound is also blocked by walls, so it is unable to travel around corners or into adjacent rooms.
Federal Trade Commission
In 2001, the Federal Trade Commission issued warnings to over 60 manufacturers of electronic pest repellents in an effort to counter false advertising and unsubstantiated claims. It mandated that claims of effectiveness at repelling pests must be supported by scientific evidence, and specifically cited concerns of long-term ineffectiveness. Manufacturers that did not follow these instructions were subject to legal action.