Sound Practice Questions

Complete the sentence.

Sound with a frequency greater than .......................... Hz is called ultrasound.

State one use of ultrasound, other than sonar.

State one use of infrasound.

A drummer hits the skin of a drum. The skin moves rapidly up and down and a sound is heard by people standing nearby.

Describe how the vibrating drum skin causes a sound wave to travel through the air.

State whether each sound in the table is infrasound, audible sound or ultrasound.

The rumble made by the elephant is very loud, but a person standing close to the elephant cannot hear it.

Explain why.

Give one reason why ultrasound is used for this test rather than audible sound.

The time between the pulse leaving the probe and the echo returning to the probe is $1.7 \times 10^{-4}$ s.

Calculate the depth $d$ of the crack below the surface of the axle.

$d$ = .............................................................. m

Describe how the human ear detects a sound wave.

A bat produces a sound of frequency 40 000 Hz. A person standing next to the bat cannot hear it.

Explain why the human ear cannot detect this sound.

Calculate the wavelength of the sound wave in air.

wavelength = .............................................................. m

The sound wave passes from the air into the water.

State what happens to the frequency of the sound wave.

Calculate the wavelength of this sound wave in the water.

wavelength = .............................................................. m

Describe how ultrasound is used to produce an image of the foetus.

Give one reason why ultrasound is used for this scan rather than X-rays.

Give one reason why low frequency waves are used for this, rather than high frequency waves.

Explain how detecting these waves at the Earth's surface gives scientists evidence about the Earth's core.

Describe how a sound wave in the air makes the diaphragm of the microphone vibrate.

The microphone produces no signal for sounds with a frequency above 18 000 Hz.

Explain why the microphone only works over a limited range of frequencies.

Calculate the depth of the seabed below the boat.

depth = .............................................................. m

Calculate the height of the shoal of fish above the seabed.

height = .............................................................. m

The echo received from the shoal of fish is much weaker than the echo received from the seabed.

Suggest why.

Explain why the worker hears two separate bangs.

The second bang is heard 4.71 s after the first bang.

Calculate the speed of sound in the steel rail.

Give your answer to 2 significant figures.

speed = .............................................................. m/s

Calculate the wavelength of the ultrasound in soft tissue.

wavelength = .............................................................. m

A different scanner uses ultrasound of frequency $7.5 \times 10^{6}$ Hz. This scanner is only used to image structures close to the skin surface.

Explain why a higher frequency is used for structures close to the skin surface.