10.3 Hearing

Question 1

How is sound produced?

Answer 1

Sound is produced by the vibration of an object.

Question 2

What is frequency?

Answer 2

Frequency is the number of vibrations per second made by a vibrating object.

Question 3

Frequency’s unit?

Answer 3

hertz (Hz)

Question 4

Correlation between object vibration and pitch.

Answer 4

The fast an object vibrates, the higher the frequency of sound produced, the higher the pitch

Question 5

How does the tuning fork have a lower pitch?

Answer 5

The longer the tuning fork, the lower the frequency, the lower the pitch.

Question 6

How is sound transmitted?

Answer 6

When an object vibrates in the air, it pushed on the surrounding air particles and causes them to vibrate

Question 7

Noise?

Answer 7

Noise is any sound that is unwanted and disturbing

Question 8

In a busy city like Hong Kong, noise may…

Answer 8

come from traffic, construction work, human voices or loud music, causing noise pollution.

Question 9

Loudness of sound is indicated by

Answer 9

Sound level, decibel (dB)

Question 10

What tool to measure sound level?

Answer 10

decibel meter

Question 11

Noise exceeding how many will have harmful effect on hearing

Answer 11

85 dB

Question 12

Harmful effects on our ear depends on

Answer 12

Sound level and duration of exposure

Question 13

Tinnitus is

Answer 13

Constant ringing in ears– damaged sensory hair cells in cochlea sending confusing signals to the brain

Question 14

Prolonged exposure to noise may cause

Answer 14

Mental stress, sleep disturbance and hearing loss

Question 15

Protect sound of hearing

Answer 15

1. Keep volume low when listening with earphones
2. Shorten time of staying in noisy environment
3. Wear ear plugs/protectors
4. Don’t pick ears with hard objects

Question 16

Sound must travel through a medium:

Answer 16

Solid, liquid or gas. Sound is transmitted through vibration of particles in these media.

Question 17

Why can’t sound travel in vacuum?

Answer 17

No air
No air particles
No particles to transmit vibration hence sound

Question 18

Speed of sound travelling in different media

Answer 18

Fastest in solid and slowest in gas

Question 19

Why does sound travels the fastest in solid, slowest in gas??

Answer 19

Solid particles are close together
Pass vibrations quickly

Gas particles are far apart
Pass vibrations slowly

Question 20

Outer ear consists of

Answer 20

Pinna, ear canal

Question 21

Middle ear consists of

Answer 21

Eardrum, ear bones

Question 22

Inner ear consists of

Answer 22

Cochlea, auditory nerves

Question 23

Pinna

Answer 23

Funnel shape. Collects sound from surroundings, direct sound into ear canal.

Question 24

Ear canal

Answer 24

Sound travels through to middle ear

Question 25

Eardrum

Answer 25

Thin membrane. Sound causes it to vibrate, vibration transmitted to ear bones

Question 26

Ear bones

Answer 26

Amplify the vibrations of eardrum, transmitted to inner ear

Question 27

Cochlea

Answer 27

Coiled structure. Inside, sensory hair cells: detect vibration and send signals

Question 28

Auditory nerves

Answer 28

Signals from sensory hair cells sent to the brain via here.

Question 29

Human's audible frequency range

Answer 29

20 Hz to 20k Hz

Question 30

Frequency application

Answer 30

Ultrasound - check condition of foetus - detect cracks in welded metal objects