Clinical hearing assessments

General hearing assessment
Pure tone audiometry (PTA)
Tympanometry
Stapedial reflex measurement
Transient evoked otoacoustic emission recordings (TOAE)

A general hearing assessment

A full hearing assessment can be carried out by an audiologist (or sometimes by an ear nose and throat doctor) in the hospital clinic, your GP or a private hearing aid dispenser [NHS Choice, 2013b]. However, some GPs may not have all the equipment required to carry out a full assessment. In such cases, your GP can make an NHS referral for you.

There are two main aims of a general hearing assessment. These are:

  • To regularly monitor the development of a baby’s or a young child’s hearing [NHS Choices, 2013b].
  • Assessing the hearing of someone who is experiencing hearing problems or has a hearing impairment [NHS Choices, 2013b].

Taking your history

In all cases, the individual’s history is taken before the hearing assessment begins. The types of questions asked are as follows:

  • Whether you have any pain or discharge in your ear
  • Whether you are experiencing tinnitus in either one or both ears
  • Whether you are experiencing any dizziness
  • Whether you are experiencing any hearing loss
  • Whether you have any previous medical problems related to your hearing or a history of hearing impairments in your family

After asking these questions, the examiner will then look into your ears to assess your ear canal for any blockage. The examiner will then proceed to carrying out the specific hearing assessments.

A hearing test takes approximately 30 minutes to complete and looks at each part of your ear to see whether it is contributing to your current hearing status [NHS Choices, 2013b].

The ear can be categorised into three parts:

  • The outer ear:
  • The middle ear:
  • The inner ear:

Outer ear assessments:
The outer ear is assessed for ear wax build up, as it can obstruct the ear canal. The ear drum is also routinely assessed.

Middle ear assessments:
Pressure in the middle ear is assessed as well as the functioning of the middle ear muscles.

Inner ear assessments:
This is where the auditory nerve and the sensorineural cells of the ear are located. Their ability to convert sound into electrical signals is assessed.

Pure tone audiometry (PTA)

Why the test is carried out

A PTA is more commonly known as a hearing test and is used to identify a person’s hearing thresholds. Different sounds are played at different volumes through headphones and a bone conductor (type of headband) [John Hopkins Medicine, 2007]. This enables the examiner to determine the degree, type and configuration of hearing loss, providing the basis for diagnosis and management.

How the test is performed

This assessment is carried out via the following steps:

  • The individual sits in a chair facing away from the equipment and has headphones placed over their ears
  • The audiologist then presents sounds of decreasing volume through the headphones
  • Once the individual hears the sound, they must press a button or raise their finger until they can no longer hear the sound
  • Once the testing using the headphones is complete a second headband may be used to test in the same way but for fewer sounds. This is called a Bone Conductor (BC) and is placed behind the ear

A PTA is often performed using a computer, however the computer does not analyse the results so the patient’s response is crucial. It is important that the individual fully understands the test and asks questions if they are at all unsure.

Tympanometry

Why the test is carried out

Tympanometry is not a hearing test, but rather a measure of ear drum movement. The ear drum is the membrane that separates the ear canal from the middle ear. This test measures how the ear drum moves in response to variable air pressures, introduced into the ear canal via the tip of the device.

How the test is performed

This assessment is carried out via the following steps:

  • The individual sits in a chair
  • An appropriate sized probe is inserted into the ear canal to create an acoustic seal
  • Variable air pressure is introduced into the ear canal via the probe; this can cause a slight blocked feeling during the test
  • Ear drum mobility is then automatically recorded in the form of a graph called a tympanogram. The final graph produced illustrates the overall functioning of the ear drum

Tympanometry takes a few minutes to complete.

Stapedial reflex measurement

Why the test is carried out

The stapedial reflex is a contraction of muscles in the middle ear, in response to a loud sound. This reflex occurs in both ears at the same time and can be measured in either one ear or both. The stapedial reflex response can help to confirm where the hearing problem is located by activating earlier than normal, later than normal or by not being present at all.

How the test is performed

This assessment is carried out via the following steps:

  1. The individual sits still and in silence
  2. A probe, the same as the one used for tympanometry, is placed in the ear that is going to be tested
  3. Another probe may be placed in the other ear, this depends on the type of test being performed
  4. Often, audiologists perform tympanometry first (See above). If not, they go straight to step 5
  5. The audiologist presents sounds of varying volume for 1-2 seconds in duration
  6. Once a reflex is detected via the probe, the examination ends

Together tympanometry and stapedial reflex measurements take approximately 5 minutes to perform.

Transient evoked otoacoustic emission recordings (TOAE)

Why the test is carried out

Otoacoustic emissions are sounds that are generated in the cochlea (part of the inner ear). The cochlea contains inner and outer hair cells that react when a sound vibration is received. A message is then sent  to the brain via the basilar membrane and the auditory nerve, indicating that a sound has been heard. A TOAE is able to record certain activity that takes place in the cochlea when it responds to sound. The assessment can be carried out on individuals who are asleep or even babies; a behavioural response is not required.

How the test is performed

This assessment is carried out via the following steps:

  • An appropriate sized probe is inserted into the ear canal to create an acoustic seal.
  • Brief click sounds are presented to the ear through the probe.
  • Otoacoustic emissions are recorded via the microphone embedded in the probe.

The probe creates an acoustic seal in the ear canal in order to maximise the capture of the otoacoustic emissions and eliminate background noise. A microphone within the probe detects the otoacoustic emissions.

At present OAE confirms cochlear function is normal. It does not confirm if a sound can be heard or processed by the individual. The auditory nerve could be damaged or firing incorrectly yet the OAE would be normal.

The test is completed for both ears in a few minutes.

 


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Created: July 2014
Review due: May 2016

First published: Tuesday 22 July 2014
Updated: Tuesday 22 December 2015