The Ear

Question 1

Sound waves are incident on a human ear.
Describe how the frequency and amplitude of the vibrations change as the wave is transmitted through the ear to the fluid in the inner ear

Answer 1

Frequency does not change

Amplitude is reduced

Question 2

Sound waves are incident on a human ear

Explain how the components of the ear act to amplify the pressure changes due to the sound wave

Answer 2

Ossicles lever system produces increase in force
Area of oval window much less than area of ear drum
Pressure = F / A so large increase in pressure

Question 3

State what is meant by the threshold of hearing and state the frequency at which the reference threshold is quoted

Answer 3

Lowest intensity of sound detected by human ear 
reference intensity (1.0 × 10–12 W m–2) is taken at 1 kHz

Question 4

Sound intensity levels are usually measured in decibels. Give two reasons why this logarithmic scale is used.

Answer 4

The ear has a logarithmic response

To accommodate a very wide range of sound intensities to which ear can respond

Question 5

Why was it necessary to introduce an adapted scale referred to as the dBA scale, which is used on some sound level matters?

Answer 5

The dBA scale takes account of the frequency dependence of the sensitivity of the ear

Question 6

What is the function of the ear drum

Answer 6

Transfers vibration of sound waves into mechanical oscillations the outer ear to the ossciles of the middle ear

Question 7

What is the function of the ossicles

Answer 7

System of levers to multiply the force (around x 1.5)

Question 8

What is the function of the windows (oval and round)

Answer 8

Allow sound vibrations to enter the fluid of the inner ear

Question 9

What is the function of the cochlea

Answer 9

Converts pressure wave in fluid into electrical signal

Question 10

What are the main differences between the dBA and the dB scales?

Answer 10

dB scale has a flat response with frequency.
dBA scale is frequency compensated.
for dBA, threshold intensities are different for different frequencies

Question 11

What is the main difference between age related hearing loss and noise-induced hearing loss?

Answer 11

loss due to age increases with frequency

loss due to noise is maximum at 4000 Hz

Question 12

State the frequency of sound at which the normal ear is most sensitive

Answer 12

3 kHz

Question 13

State the main features of hearing loss in terms of frequency response for
age-related hearing loss

Answer 13

as f increases, loss increases

Question 14

State the main features of hearing loss in terms of frequency response for
noise-related hearing loss

Answer 14

loss is maximum at 4 kHz

Question 15

Define intensity

Answer 15

power per unit cross-sectional area (in path of wave)

Question 16

State what is meant by attenuation and what causes it.

Answer 16

reduction in intensity/energy/power as wave travels through a medium due to absorption/scattering/diffraction

Question 17

Define the threshold of hearing, Io

Answer 17

Minimum intensity heard by normal / average ear

At frequency of 1kHz

Question 18

Describe how the vibrations of a sound wave are received by the outer ear and transmitted to the inner ear.

Answer 18

longitudinal/pressure waves in the ear canal
forces eardrum into mechanical vibrations.
(Mechanical) vibrations (passed through middle ear) by a lever
system/series of bones/named bones to the oval window
sets up pressure waves in fluid in cochlea

Question 19

Explain how the pressure changes due to the sound wave are amplified by the ear.

Answer 19

force increased by the action of the lever system/series of
bones/named bones; value F × 1.5
area of oval window &laquo_space;area of the eardrum ; value A/20
effect of pinna in increasing intensity in ear canal

Question 20

intensity is proportional to

Answer 20

amplitude squared

Question 21

The ear acts as a

Answer 21

Transducer, converting sound energy into electrical energy

Question 22

Where does the db and dba scale meet?

Answer 22

1000 Hz

Question 23

Draw a graph of intensity against frequency (log)

Answer 23

Intensity scale (10^-2) to 10^2, at 1 is the threshold of feeling
The curve starts at 20 and ends at 20000, with the minimum point at 3000 hz

Question 24

Increase in loudness is proportional to

Answer 24

log(new intensity/original intensity)