To put it simply, a hearing test is used to determine the sensitivity of a person’s hearing. Based on the test result, audiologists and ENTs will evaluate whether therapy is needed, and if so, what would be most beneficial for the patient. Ideally hearing tests aren’t just performed when someone is experiencing perceived problems with their hearing, but also as a routine measure for early intervention.
Testing the hearing of newborn babies is now a regular part of the clinical assessment. Identifying hearing loss early ensures interventions can be implemented from a very young age, assisting with the development of language, speech, and communication skills.
Regular hearing tests, screenings and check-ups should also be part of every adult’s health regime. Unfortunately, most adults don’t tend to seek out a hearing test until they become aware of a problem, despite recommendations that all adults under 50 should have their hearing checked at least once a decade, and following this, on an annual basis.1
Preparing for the audiometric test
Prior to performing an audiometry test, it’s recommended that an otoscopic examination is carried out to check the condition of the outer ear and the tympanic membrane (ear drum). Otoscopy will help detect whether there is a tympanic membrane perforation, stenosis, cerumen (ear wax) or foreign bodies within the ear canal. For complete accuracy, audiometric tests should be carried out on clean ear canals to ensure the sound can reach the middle ear without any restrictions.
Before the test, the patient is often asked to complete a questionnaire regarding their medical history, any previous noise exposure, and any current symptoms they may be experiencing.
Tests should be carried out in a room where background noise levels are no more than 30 dBA, or, for optimal test conditions, in an audiology booth. If it isn’t possible to perform the hearing test in an audiology booth, noise-reducing enclosures (such as Audiocups), can be used to reduce the overall noise levels and create more reliable hearing thresholds.
The types of audiometry tests
Hearing tests usually include tone audiometry as well as speech audiometry measurement. This allows experts to distinguish between a conductive hearing loss and a sensorineural hearing disorder. A screening audiometry test usually takes less than 3 minutes to perform and can determine whether further diagnostic testing is required.
Using pure tone audiometry for air and bone conduction
Air conduction audiometry is the gold standard of hearing screening. Once the air conduction test has been carried out, it might be necessary to carry out a bone conduction test for further investigation into the hearing diagnosis. During the hearing test, the patient will either wear a set of air conduction headphones, or a bone conduction vibrator, in order to hear a range of sounds. The sounds are directed to each ear, one at a time. For ease, the headphones are colour-coded with blue for the left ear, and red for the right ear.
The patient is given instructions to either raise their hand, or press a response button, whenever they hear a tone. Some of the sounds presented will be soft and barely audible so it’s essential that the patient listens carefully. Their response to the test tones will indicate when they can and can’t hear the tone. The quietest sounds at which the individual can hear at each frequency is called a threshold.
The test procedure can be adapted according to the age of the patient and their attention span. In some cases, it might be better to test fewer frequencies accurately than to try and test the full range.
The aid of masking assistant
Masking is also something that can be used with an air or bone conduction test when investigating asymmetrical hearing loss. In this instance, a masking noise is played into the ‘good‘ ear in order to keep the cochlea busy, so it doesn’t assist the hearing in the test ear. This method is used to identify the correct hearing threshold of the ear with the worst hearing.
Interpreting test results
Following the test, results will be shown on a graph called an audiogram. The audiogram will show the quietest sounds the individual can hear at each frequency. The vertical axis of the audiogram shows the decibel intensity range/volume of the sound and the horizontal axis shows the frequency/pitch of the sound. See example below:
Using speech audiometry
Speech audiometry tests are used for diagnosis. Depending on the findings of the tone audiogram, the speech tests will then evaluate the recognition and detection threshold of the patient.
Speech audiometry is usually used whilst fitting a hearing aid to help identify the benefits of the hearing system. It can also be used to help detect specific types of hearing loss. It has become more common to perform speech audiometry (particularly in noise) for occupational health purposes, because pure tone tests tend not to provide enough evidence about a patient’s ability to understand speech.
The type of speech test used depends on several factors, including the occasion, the age of the patient, and/or the country. Speech tests will also vary in language, overall test time, and procedure. The level of background noise is also a consideration when performing the test.
The patient is either positioned in a free field environment where the signal(s) are presented via a loudspeaker, or alternatively the signal(s) may be presented via headphones. The subject is asked to repeat the word that they hear so that the professional completing the test can identify the speech recognition threshold (SRT), the speech detection threshold (SDT) or the word recognition score (WR).
Diagnostic audiometry equipment
Amplivox supply a range of diagnostic audiometers which provide air and bone conduction, masking, and also allow for speech audiometry testing, regardless of language. Files can be presented via live speech, or via headphones with the use of a CD or MP3.
For more information on our extensive range of class-leading diagnostic audiometers please visit our webpage, contact our customer support team on +44 (0)1865 880 846 or email.
1Ear Exams: When and Why Do I Need One? (webmd.com)