Question: What is ultrasound

Gill Harrison answered on 4 Mar 2019:

Ultrasound is high frequency sound waves (higher than 20kHz) that are higher than those sounds you can hear as a human (usually somewhere between about 20Hz and 20kHz). Ultrasound is used to measure distances or to locate structures / things within matter, for example we use it in medicine to detect structures within the body and also to measure them. Whales and dolphins use ultrasound (sonar) to locate fish, so they know which direction to swim in to get lunch. Bats also use ultrasound to detect insects, whilst in flight.

I’ve seen news reports where shops were using frequency of sound within the audible range (the range you can hear, but at the higher end of the frequency range, closer to 20kHz) to try and stop young people ‘hanging around’ areas in groups. This is because younger people often can hear the higher pitched sounds, but adults can’t. There’s a link to a BBC article about it here: http://news.bbc.co.uk/1/hi/7240180.stm

Dogs can hear higher frequency sounds, which is why humans can’t hear a dog whistle, but the dog does and comes running back for a treat 😉