There are a variety of diagnostic tests used to determine the type and extent of a patient’s hearing loss. The most common tests used by audiologists are:
Pure-tone testing is used to determine the faintest tones a patient can hear at a range of pitches. Patients wear earphones and each time they detect a tone, they raise their hand. This can also be performed with a bone vibrator, which instead of emitting audible sounds sends tiny vibrations in to the inner ear. Comparing the results from both versions of this test helps pinpoint the part of the ear responsible for hearing loss.
Children at birth can only be evaluated with objective tests (such as EEG), but by 6 months of age, a child’s hearing can be checked with this test. Earphones are not used; instead, the sound is broadcasted though speakers in a specially designed booth. To confirm which sounds a child heard, they are trained to either look in the direction of the sound or to perform an action, such as putting a toy in a box, each time they detect a sound.
The results from this test are recorded on an audiogram. This chart is a visual representation of the loudness (decibels) of each pitch (hertz) the individual can detect.
Speech testing consists of two measurements, a patient’s speech-detection threshold (SDT) and their speech-recognition threshold (SRT). The SDT determines the lowest level of speech a patient can hear. A list of words is read aloud to the patient and they indicate if they heard each word. The SRT also determines the lowest level of speech a patient can hear, but this time the patient is required to repeat the words back to the tester. These tests are performed in both a quiet and a noisy environment.
The results from this test are used to confirm the results from pure-tone testing. They can also help to predict how well a patient may do with amplification and can provide information about any underlying issues with the nerve, which may cause the hearing loss to be progressive in nature.
Acoustic Immittance Testing
Tympanometry is used to see how the middle ear, eardrum and Eustachian tube are functioning. Air pressure is pushed into the ear canal, which causes the eardrum to move back and forth.
This test presents loud tones to each ear and measures how the middle ear reacts. This test is able to predict hearing levels and evaluate neuronal pathways to determine whether there is an underlying issue.
Auditory Brainstem Response (ABR)
This test measures the pathways in the brain responsible for hearing. Electrodes are placed around the patient’s forehead and ears; in order to get a good reading the patient is asked to lie down and stay still for the duration of the two-hour test. The patient’s brain wave reaction to sound is measured.
While a non-invasive test, sedation is typically needed if this test must be performed on a child that cannot stay still.
There are a few variations of this test used to specifically evaluate the patient’s equilibrium: Electrocochleography (ECoG) and Vestibular Evoked Myogenic Potentials (VEMP).
This is a group of tests used to evaluate the patient’s balance system. The tests record the patient’s eye movement with infrared goggles in response to various stimuli (lights and position changes). Such tests include: rotary chair testing, sensory organization or postural stability testing, Dynamic Visual Acuity, active head rotation and Electronystagmography (ENG)
Otoacoustic Emission Testing (OAEs)
Otoacoustic emissions are the sounds given off by the inner ear when stimulated by sound. This test is used to determine if there is damage to the hair cells in the cochlea and to determine a possible cause for ringing in the ears (tinnitus). Since the emissions are nearly inaudible, a small plug is placed into the ear in order to detect the ear’s reaction to a series of clicks.
This test is also typically used as part of a newborn hearing screening.