To determine an individual’s level of hearing or investigate hearing loss, an assessment needs to take place. There are several types of hearing tests that focus on different aspects of the hearing. Hearing tests can be divided into two types – screening and diagnostic. As the titles suggest, screening identifies if there is a problem and diagnostic identifies what the problem is. Measuring your level of hearing can either be done subjectively (the individual responds to auditory stimuli given by the tester) or objectively (the individual cooperates while the tester measures physiological responses to auditory stimuli).
Pure Tone Audiometry
The most common subjective measure of hearing is pure tone audiometry testing both air and bone conduction. The results are plotted on an audiogram (see below) and this gives an indication of the hearing ability of each ear. our ears will work better at picking up some frequencies than others.
There are also specific tests for the middle ear and tests for the inner ear and auditory pathways. It may take a couple of different tests to exactly pinpoint the true cause of a hearing impairment.
The audiogram above shows that the right ear has a normal hearing range, the left ear has a significant hearing loss which is worse in the higher frequencies.
Middle ear testing
Tympanometry or Acoustic Reflex Measures are procedures to measure the functioning of the middle ear. Tympanometry measures the feedback from sounds put into the ear and reflex measurements focus on the movements of the muscles in the middle ear in response to sound.
There are several objective measurements for testing sensorineural hearing impairments:
- Auditory brainstem response (ABR) measures the response along the auditory pathway by taking measurements from electrodes on the head.
- Auditory Steady State Response (ASSR) is relatively new test and is often done in conjunction with ABR test. This test also measures the brains response to sound.
- Evoked Otoacoustic Emissions are a measurement of the low-intensity sound energy that is generated by the cochlear when it responds to sound. This is measured by sending sound into the ear and placing a microphone in the ear canal to measure the cochlear’s response.
These tests are commonly performed on newborn babies or infants to assess for hearing loss. Along with these tests, children may participate in a behavioural, or play audiometry assessment where the audiologist produces sounds and observes the babies behaviour or response to sounds.
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