Sound and ultrasound

Question 1

describe the process of human ears detecting sounds: (4)

Answer 1

• Sound waves enter the ear canal and cause the eardrum to vibrate.
• Three small bones transmit these vibrations to the cochlea.
• This produces electrical signals which pass through the auditory nerve to the brain,
• where they are interpreted as sound.

Question 2

what is the frequency of a sound wave related to?

what are high and low frequency sound waves? (2)

Answer 2

the pitch that is heard

• high frequency sound waves are high pitched
• low frequency sound waves are low pitched

Question 3

what is the amplitude of a sound wave related to?

what are high and low amplitude sound wave? (2)

Answer 3

the volume of the sound

• high amplitude sound waves are loud
• low amplitude sound waves are quiet

Question 4

what is the cochlea only stimulated by?

-what does this mean for humans?

Answer 4

a limited range of frequencies.

-humans can only hear certain frequencies.

Question 5

what is the range of normal human hearing?

what are sound waves above/ below this range called?

Answer 5

20 Hertz (Hz) to 20,000 Hz (20 kHz)
-infrasound and ultra sound

Question 6

what do ultra sound waves have?

Answer 6

a frequency higher than the upper limit for human hearing – above 20,000 Hertz (Hz)

Question 7

explain why a dog can hear the ultrasound produced by a dog whistle, but humans cannot.

Answer 7

Different species of animal have different hearing ranges

Question 8

typical uses of ultrasounds: (4)

Answer 8

• breaking kidney stones
• cleaning jewellery
• foetal scanning
• detecting cracks in machinery

Question 9

describe how sound waves are used in these two applications:

breaking kidney stones & cleaning jewellery

Answer 9

the vibrations caused by the ultrasound shake apart the dirt or kidney stones, breaking them up.

Question 10

what does ultra sound imaging create?

-give an example of this

Answer 10

a picture of something that cannot be seen directly,

-an unborn baby in the womb, or faults and defects inside manufactured parts.

Question 11

what do foetal scanning & detecting cracks in machinery rely on?

Answer 11

what happens when ultrasound waves meet the boundary between two different materials

Question 12

describe what happens when ultrasound waves meet the boundary between two different materials: (3)

Answer 12

• some of the ultrasound waves are reflected at the boundary
• the time taken for the waves to leave a source and return to a detector is measured
• the depth of the boundary can be determined using the speed of sound in the material and the time taken

Question 13

equation for measuring the depth of a boundary:

Answer 13

d = v × t

depth (m) = wave speed x time

Question 14

what can high frequency sound waves be used for? (2)

Answer 14

detecting objects in deep water

to measure water depth

Question 15

what can be used to calculate the distance of the reflecting surface or object?

what is this process called?

Answer 15

• the time between a pulse of sound being transmitted and detected
• the speed of sound in water

-echo sounding

Question 16

what is echo sounding applied in?

for what purpose?

Answer 16

• in sonar systems

- to find shipwrecks, submarines and shoals of fish

Question 17

what can infrasound be used to do?

-using what?

Answer 17

investigate the internal structure of our planet

-using the seismic waves produced by earthquakes that can be classed as infrasound waves

Question 18

what are the 4 layers of the earth?

Answer 18

crust, mantle, inner core and outer core

Question 19

describe the paths of seismic waves and why are they this way?

Answer 19

-paths are curved as the waves refract due to the gradually changing density of the layers.

Question 20

what can seismic waves only travel through?

how do we know this? (2)

Answer 20

-solids.

• because they are not detected on the opposite side of the Earth
• which suggests that the mantle has solid properties, but the outer core must be liquid.

Question 21

what can P-waves travel through?

where are they detected?

Answer 21

• solids and liquids.

- on the opposite side of the Earth.

Question 22

in relation to P-waves, what do the refractions between layers cause?

what can we deduce from them?

Answer 22

-two shadow zones, where no P-waves are detected –

the size and positions of these shadow zones indicate there is a solid inner core.