# 'A' Level Medical Option Questions - The Ear

Q10.

(a) State the frequency of sound at which the normal ear is most sensitive.

3 kHz

(1 mark)

(b) State the main features of hearing loss in terms of frequency response for

(i) age-related hearing loss,

A sound level perception curve steadily decreases towards higher frequencies - as frequency increases the loss increases

(ii) noise-related hearing loss.

There is a 'dip' in a sound level perception curve at about 4 kHz - loss is concentrated around 4 kHz

(2 marks)

(c) At the site of a machine in a factory, a sound meter was used to measure the sound level. The relative intensity level with the machine operating was 86 dB. The sound intensity reaching the meter when the machine was not operating was 7.0 × 10–5 Wm–2.

I0 = 1.0 × 10–12 W m–2

(i) Show that with the machine operating, the sound intensity reaching the meter was about 4 × 10–4 Wm–2.

When the machine was operating and there was background noise.

intensity level = 10 log10(I/Io)

86 = 10 x log10 (I/(1.0 x 10-12))

I = 108.6 x 1.0 x 10-12

I = 3.98 x 10-4 QED

(ii) Calculate the relative intensity level due to the machine alone.

I = 4.0 x 10-4 - 7.0 × 10–5 = 3.3 x 10-4

intensity level = 10 log10(I/Io)

= 10 log10(3.3 x 10-4/1.0 x 10-12)

intensity level = 85 dB

(4 marks)

(Total 7 marks)