Ability to hear ultrasound

Backup Sensors use Ultrasonic (Ultrasound) technology.

Ability to hear ultrasound

Some animals, such as dogs, dolphins, bats, and mice have an upper frequency limit that is greater than that of the human ear and thus can hear ultrasound. Children can hear some high-pitched sounds that older adults cannot hear, as in humans the upper limit pitch of hearing gets lower with age (a cell phone company has used this to create ring signals only able to be heard by younger humans[1]). This frequency limit is caused by the middle ear that acts as a low-pas filter. If ultrasound is fed directly into the skull bone and reaches the cochlea without passing through the middle ear, much higher frequencies (up to about 200 kHz) can be heard. This effect (sometimes called ultrasonic hearing) was first discovered by divers exposed to a high-frequency (ca. 50 kHz) sonar signal.