Rose Wilson of Dunedin asks :-
If animals have such sensitive hearing how can they live with household noises?
Christine Thomson, of Massey University's Institute of Veterinary, Animal and Biomedical Sciences, responded.
Hearing is the ability to detect sound. In most mammals, sound vibrations in the air are collected by the external ear and cause vibration of the eardrum. This sets a bridge of tiny bones vibrating in the middle ear. In turn, these bones set fluid vibrating in the inner ear, which stimulates electrical impulses in the auditory nerve.
The nerve impulses are perceived by the brain as sound of different volume/amplitude and frequency/pitch. Volume, measured in decibels, obviously refers to how loud the sound is, whereas frequency, measured in Hertz (Hz), is how high or low the sound is, like the treble and bass in music.
The frequency range that humans can hear is called sonic and extends from 64 to 20,000Hz. Sounds pitched above or below this range are called supersonic and infrasonic, respectively.
Animals, such as dogs and cats that share our living space have more sensitive hearing as they can hear much higher frequencies than humans. Dogs can hear frequencies up to 45,000Hz and cats up to 65,000Hz (these figures are approximate). This is why most humans cannot hear dog whistles, which are pitched above 20,000Hz. Compared with humans, cats and dogs would normally hear a greater range of sounds because of their more sensitive hearing. However, household noises are only likely to cause them distress if the volume is too high. This is similar to us, where noise becomes painful when the volume is too loud.
Hearing ranges vary greatly amongst animals. Bats can hear sounds up to 110,000Hz which they use for echolocation. Conversely, elephants can hear infrasound as low as 16 Hz, which they use for communication over long distances.