A LevelPhysicsAQARevision NotesMedical PhysicsPhysics of the EarDefects of Hearing

Defects of Hearing (AQA A Level Physics): Revision Note

Exam code: 7408

Katie M

Written by: Katie M

Reviewed by: Tim

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Defects of hearing

  • Deterioration of hearing can occur due to:

    • age

    • exposure to excessive and prolonged noise

    • genetic factors and disease

  • Depending on the type of hearing loss, the response is different for different frequencies of sound

  • Hearing loss due to ageing:

    • occurs at all frequencies

    • with the greatest losses at higher frequencies

  • Hearing loss due to excessive noise:

    • occurs in the frequency range the person was exposed to

    • with the greatest loss at 4 kHz

Line graph of hearing loss in decibels against frequency from 0–15 kilohertz. Normal ear remains at 0 dB. A machine-induced loss peaks at about 28 dB at 4 kHz. Age loss increases to about 55 dB by 11 kHz.
Depending on the type of hearing loss, different responses to frequencies of sound are found to deteriorate

  • The degree of hearing loss can be tested by obtaining equal loudness curves and comparing the results with the curves for normal hearing

  • The same, but inverted, curve can be obtained using the dBA scale

Paired line graphs of hearing-response curves A, B and C against frequency in hertz: intensity level in decibels on the left and intensity level in dBA on the right. A is green, B blue and C red; C has a notch near 4 kilohertz.
Curve A shows the response for a young person with no hearing loss. Curve B shows the response for an older person with hearing loss due to ageing. Curve C shows the response for a young person with hearing damage due to excessive noise

Worked Example

A hearing test was used to obtain threshold hearing audiograms for a group of people. The diagram below shows the audiogram obtained for a person with normal hearing.

Line graph of intensity level from 0–110 dB against frequency from 0–15 kilohertz. The curve falls from about 78 dB at 30 hertz to 5 dB at 3 kilohertz, then rises to 35 dB at 15 kilohertz.

On the graph, sketch curves to show:

(a) a curve labelled X to show a person suffering from hearing loss due to excessive noise [2]

(b) a curve labelled Y to show a person suffering from hearing loss due to old age. [1]

Answer:

Part (a)

Line graph of intensity level from 0–110 dB against frequency from 0–15 kilohertz. The curve falls from about 78 dB at 30 hertz to 5 dB at 3 kilohertz, then rises to 35 dB at 15 kilohertz. Green curve X is added to the normal-hearing curve, falling from about 90 dB at 110 hertz to 27 dB near 2 kilohertz, peaking at 60 dB at 4 kilohertz, then rising to 98 dB.

  • Curve X: hearing loss increases up to 4 kHz [1 mark] then decreases after this frequency [1 mark]

Part (b)

Line graph of intensity level from 0–110 dB against frequency from 0–15 kilohertz. The curve falls from about 78 dB at 30 hertz to 5 dB at 3 kilohertz, then rises to 35 dB at 15 kilohertz. Green curve X is added to the normal-hearing curve, falling from about 90 dB at 110 hertz to 27 dB near 2 kilohertz, peaking at 60 dB at 4 kilohertz, then rising to 98 dB. Green curve Y showing age-related hearing loss is added showin a smooth curve above normal hearing that rises at high frequencies.

  • Curve Y: loss increases as frequency increases [1 mark]

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Author
Reviewer
Katie M

Author: Katie M

Expertise: Curriculum Expert

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

Tim

Reviewer: Tim

Expertise: Content Creator

Timothy graduated with a first class degree in Mathematics and Physics from the University of Warwick. After working as a postgraduate researcher, Timothy has worked as a content creator for various online revision platforms, creating physics resources for a range of levels and exam boards.