Ultrasound and Infrasound

Question 1

What can humans hear?

Answer 1

Humans can hear sounds from 20 Hz to about 20,000 Hz. However, younger people can hear much higher-pitched sounds than older people.

Question 2

What is ultrasound?

Answer 2

Ultrasound is sound with frequencies above 20,000 Hz.

Question 3

What animals can hear ultrasound and what do they use it for?

Answer 3

Humans can’t hear ultrasound, but some animals, such as dolphins can and use it for communication.

Question 4

What is infrasound?

Answer 4

Infrasound is sound with frequencies below 20 Hz.

Question 5

What animals can hear infrasound and what do they use it for?

Answer 5

Humans can’t hear infrasound, but some animals, such as whales can and use it for communication.

Question 6

What happens to sound the closer the particles in the materials are?

Answer 6

The closer the particles in the material, the faster sound travels. This means that sound travels fastest in solids and slowest in gases.

Question 7

What is ultrasound used for?

Answer 7

• the communications between some animals
• foetal scanning - to safely see inside the body
• very high frequency ultrasound (about 1.5 MHZ) is used to see fine detail
• sonar - used by ships to determine the depth of water

Question 8

How does solar work?

Answer 8

Solar is a technique used by ships to detemine the depth of water. It works by having pulses of ultrasound reflected off the bottom of the seabed. The time delay between sending the pulse and receiving the echo is used to then calculate the distance traveled.

Question 9

What is echolocation?

Answer 9

Echolocation is the same method as solar used by ships, but instead it is used by dolphins and bats to find their prey.

Question 10

What is infrasound produced by?

Answer 10

Infrasound is produced naturally by volcanoes, avalanches, ocean waves, hurricanes, earthquakes, meteorite explosions and animal movements. It is also produced by human activity, such as drilling oil, and nuclear and chemical explosions.

Question 11

How far can infrasound travel?

Answer 11

Infrasound can travel hundreds of kilmetres through the Earth and atmosphere.

Question 12

What do humans use infrasound for?

Answer 12

to detect and monitor:

• animal movements in remote locations
• volcanic activity and meteorite strikes

Question 13

How can the distance travelled by ultrasound pulse be calculated?

Answer 13

distance travelled by ultrasound pulse = speed of ultrasound x time delay

Question 14

Are sound waves transverse or longitudinal?

Answer 14

Sound waves are longitudinal.

Question 15

What frequency will a high pitched sound have?

Answer 15

A high pitched sound will have a high frequency.