Ultrasound - Quick Project Ultrasounds are sound waves with frequency beyond the human limits, therefore humans are unable to hear them. It even travels at exactly the same speed as sound in any medium. Humans can hear sound within the frequency range of about 20 to 20, 000 Hz, so any sound above 20 k Hz is ultrasound. Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines. Ultrasound has very high frequency vibrations and can be used to clean things.

Really dirty teeth can be cleaned superbly in this way. Really delicate mechanisms, such as in antique clocks and watches, can also be safely cleaned. Ultrasound for scanning is the most popular medical use. This is safer than using X-rays.

Unborn babies can be seen by moving an ultrasonic transmitter across the mother's stomach. The sound waves will be projected from the transmitter and the waves are able to travel from one part of the human being to the other. As it hits a tissue or an organ, some waves reflects and gives of echos which can build up a picture on the TV screen. The shorter the wavelength is, the finer the detail of the picture is. Its use in scanning goes far beyond pregnancies. Many other parts of the body are analysed using it (bladder gallstones, the heart, etc.

). Ultrasound can even check airplane wings for cracks that would be invisible on the surface. Ships use SONAR to determine the depth of water they are in. Ultrasound is used here because they have a higher frequency and this allows it to penetrate further.

However, the disadvantage is that it might scare the fishes away as it would be too noisy for them. By timing how long the echo takes to come back, and knowing the speed of sound in water, the depth can be calculated. Animals like dolphins, whales and bats use ultrasound frequencies to help them get around as they have poor eye sight. They make the noises from their mouths and by listening to the time it comes back, it will know if there are any obstacles in front of them. This is called echolocation.