The testing, or evaluation of hearing, is performed by our Audiologist, Steven W. Sick M.S., CCC-A. The evaluation includes a battery of tests that are listed below. These tests are quick, painless, and easy to perform. One test, the audiogram, is a subjective test that measures your best possible hearing, while the other tests are subjective and complement the audiogram, providing an accurate assessment of the degree and cause of the hearing impairment. This will allow us to implement the best possible treatment plan.
The following is a description of each test included in our diagnostic battery:
A graph of your hearing levels, measuring the softest sounds you can hear. This graph is laid out like a piano keyboard, with low to high frequencies (pitches) going from left to right. Loudness, measured by decibel (dB) is arranged with soft sounds on the top to loud sounds on the bottom. The graph is completed using marks that represent each ear: black “X” representing the left ear, and a red “O” representing the right ear. (provide link or photo of audiogram) Using this chart, the amount of hearing loss is determined. The further the marks representing each ear are towards the bottom of the graph, the greater the hearing loss.
The audiogram is obtained using equipment called an audiometer, which allows for different pitches and loudness levels to be presented to the patient via calibrated headphones. The patient responds to each tone presentation by pressing a button or raising his/her hand when hearing the tone – even if the tone is barely heard. Remember, the goal is to obtain the best possible hearing.
Bone conduction testing is also performed during the audiometric evaluation. In this test, a bone conduction vibrator is positioned behind the ear on the mastoid bone. This test evaluates the functioning of the inner ear system. As with headphones, tones are presented at different pitches and loudness levels, again determining the softest level at which the patient can hear the tone. The bone conduction results are represented by angles: a black “>” for left and a red “<” for right. Along with tones obtained via headphones, results obtained by the bone conduction vibrator assist the audiologist in determining the cause of the hearing loss.
Speech discrimination testing is also performed during the audiogram. This score is a representation of how well an individual can repeat single syllable words at a comfortable loudness level in each ear. This score is a general indicator of the functioning of the auditory nerve and auditory cortex, and is also used as a predictor as to how well an individual who has hearing loss will function with hearing aids. Another speech recognition test, the Speech Reception Threshold, evaluates the lowest or softest level at which the patient can correctly repeat 2 syllable words.
Degrees of Hearing Loss
Based on the results of the audiogram, the degree of hearing loss can be determined. The degree of hearing loss over the range of frequencies (pitches) along with the ability to understand speech is obtained. The degree of hearing loss is categorized as follows:
Normal – (-10dB to 20dB)
Mild – (25dB to 40dB)
Moderate – (45dB to 60dB)
Severe – (65dB to 90dB)
Profound – (95dB or greater)
An example of a patient with high frequency hearing loss.
Sound Field Testing
For infants and children, or difficult to test patients who are unable to understand the behavioral task required for the audiogram (raising hand when hearing the tone), Sound Field Testing is performed. During this procedure, the child sits on the parent’s lap. Sounds are presented via speakers in a sound proof room. The audiologist watches the child’s responses to the sounds. The audiologist also looks for responses such as eye blinks, eye shifting, body movements, and ceasing of body movements. Older children will turn toward the sound. When turning toward the sound, the child will see a lighted toy as a reward for finding the sound.
This is a subjective procedure that examines the functioning of the middle ear and mobility of the tympanic membrane (eardrum) and ossicular chain (3 tiny bones in the middle ear space called the malleus, incus, and stapes, or hammer, anvil and stirrup). Results are obtained by creating variations of air pressure within the ear canal while generating a tone into the ear canal by using a small probe in the ear canal. The sound strikes the tympanic membrane, causing vibration of the middle ear system. Some of this sound is reflected back and measured by the instrument. The more stiff the middle ear system, the more sound reflects back. In normal middle ear functioning, the air pressure in the ear canal is the same as within the middle ear cavity. Thus, the maximum sound is transmitted through the middle ear. With a stiff middle ear system (i.e., middle ear effusion, or fluid within the middle ear space), more sound is reflected back and measured. Ultimately, Eustachian tube functioning is evaluated, as the Eustachian tube, located behind the nose/throat area and channeling to the middle ear space, must ventilate our middle ear.
Stapedius Reflex Testing
Another measurement of middle ear functioning done in conjunction with Tympanometry, this procedure measures the muscle contraction that occurs within the middle ear system. With semi-loud tone stimuli, the stapedius and tensor tympani muscles, located within the middle ear space and attaching to the malleus and stapes, contracts. This contraction pulls the stapes away from the oval window (that connects to the ossicular chain to the cochlea), and the malleus away from the eardrum, thus decreasing the vibration energy to the cochlea. Thus, the stapedius reflex acts as a “protection system”, and occurs with normal functioning of the middle ear system. Absence of this reflex is an indicator of middle ear pathology, such as middle ear effusion, otosclerosis, or cholesteatoma. Absence of stapedius reflexes can also be an indicator or predictor of sensorineural hearing loss. Being a subjective test, like tympanometry, this is a valuable testing procedure for the difficult to test population.
Distortion Product Otoacoustic Emissions
Otoacoustic emissions are tiny sounds, or sound energy, that emerge from the inner ear shortly following exposure to external sound. Using a small, comfortable probe tip in the ear canal, sound stimuli consisting of 2 simultaneous tones of different pitches are sent into the cochlea. The resulting sound energy from the hair cells of the cochlea are reflected back into the ear canal, where they are measured by the instrument. Thus, cochlear hair cell functioning can be obtained. This information is used to screen hearing of infants, children, and difficult to test patients. Results from Distortion Product Otoacoustic Emissions can also estimate hearing sensitivity and differentiate between sensory (cochlear damage) and neural (auditory nerve, or VIIIth nerve damage) causes of hearing loss.
Auditory Brainstem Response (ABR) Testing
This procedure is a neurological test that measures electrical or neurological signals that are induced by the auditory, or VIIIth nerve within the brainstem as it responds to sound. Thus, the ABR is an objective test that evaluates the functioning of the auditory nerve. The auditory nerve may be affected by a benign tumor called an acoustic neuroma that arises near the auditory nerve. Sometimes, a loss of mylin, or a layer of insulation that covers the auditory nerve can cause loss of functioning. In most cases, these types of auditory nerve disorders will affect only one ear. Thus, if hearing loss affects one ear, or hearing loss is more pronounced in one ear, ABR is usually indicated. Results of the ABR also help to determine if a sensorineural hearing loss is due to cochlear damage or auditory nerve damage, and can be a good predictor of success for hearing aid use. The ABR is a painless, non-invasive test involving attachment (or taping) of electrodes to the forehead and behind each ear, along with small insert phones to provide the sound stimuli. The ABR results are obtained while the patient is relaxing, or even asleep. Being subjective, painless, and easy to administer, the ABR can be used to screen hearing of infants, young children, and difficult to test patients.