The Effects of Ultrasonic Bird Repellers on Cats in the House

Principle

• Hearing ultrasonic signals is supposedly quite unpleasant, and these repellants operate under the assumption that birds will be repulsed by these unpleasant effects, thus keeping the birds physically away from the area covered by the repellant. However, according to scientists from the University of California presenting at the Fifteenth Vertebrate Pest Conference, birds can become accustomed to, or habituate, to noises heard continuously – even those that are initially unpleasant – and bird hearing ranges between 0.05 and 29,000 Hz, depending on the species. For species with ranges below ultrasonic sound levels, these noise repellents are not effective.

Humans

• Ultrasonic repellants are seldom audible to humans. Human hearing has a sensitivity to sound up between 16,000 and 20,000 Hz, although some rare individuals can distinguish sound up to 24,000 Hz.

Cats

• Cats have a range of hearing, on the lower end, similar to humans. Cats can, though, hear and distinguish sounds up to 64,000 Hz on the upper level of their hearing. This makes them extremely susceptible to ultrasonic frequencies.

Effects

• Ultrasonic waves create heat and radiation which can damage cells and nerves. Long-term exposure to ultrasonic sound can cause pain, nausea, hearing loss or deafness to all animals – including humans, even though the frequency is most commonly inaudible. Cat hearing is up to four times more sensitive than humans, as their ears are designed to assist with hunting -- they can distinguish differences in less than 1/10 of a tone, and the size of the sound’s source – and act as a counterbalance for their characteristic leaping and movement. Ultimately, ultrasonic repellants would not only cause injury, they would cause immediate distress.