The Audiology clinic is committed to serving adults and children with hearing health care needs. We carry out comprehensive hearing evaluation for patients referred to us at Ahmadi Hospital. In addition to identifying and diagnosing hearing loss among these patients, we have also established the new born hearing screening program, periodical hearing screening program (for hearing conservation of employees exposed to noise) and other services . A battery of tests are conducted at the clinic, which include:
Pure Tone and Speech Audiometry
Audiometry is the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and make use of an audiogram.
Tympanometry is an examination used to test the condition of the middle ear and mobility of the eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal. Tympanometry is an objective test of middle-ear function. It is not a hearing test, but rather a measure of energy transmission through the middle ear. The test should not be used to assess the sensitivity of hearing and the results of this test should always be viewed in conjunction with pure tone audiometry.
The acoustic reflex (or stapedius reflex, attenuation reflex, or auditory reflex) is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high-intensity sound stimuli.
When presented with a high-intensity sound stimulus, the stapedius and tensor tympani muscles of the ossicles contract.The stapedius stiffens the ossicular chain by pulling the stapes (stirrup) of the middle ear away from the oval window of the cochlea and the tensor tympani muscle stiffens the ossicular chain by loading the eardrum when it pulls the malleus (hammer) in toward the middle ear. The reflex decreases the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain. The acoustic reflex normally occurs only at relatively high intensities; activation for quieter sounds can indicate ear dysfunction. The pathway involved in the acoustic reflex is complex and can involve the ossicular chain (malleus, incus and stapes), the cochlea (organ of hearing), the auditory nerve, brain stem, facial nerve and other components. Consequently, the absence of an acoustic reflex, by itself, may not be conclusive in identifying the source of the problem.
An otoacoustic emission (OAE) is a sound which is generated from within the inner ear. Having been predicted by Thomas Gold in 1948, its existence was first demonstrated experimentally by David Kemp in 1978 and otoacoustic emissions have since been shown to arise by a number of different cellular mechanisms within the inner ear. Studies have shown that OAEs disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and the clinic as a measure of inner ear health.
Broadly speaking, there are two types of otoacoustic emissions: spontaneous otoacoustic emissions (SOAEs), which can occur without external stimulation, and evoked otoacoustic emissions (EOAEs), which require an evoking stimulus.
Brain Stem Auditory Potential (BAEP)
In human neuroanatomy, brainstem auditory evoked potentials (BAEPs) are very small electrical voltage potentials which are recorded in response to an auditory stimulus from electrodes placed on the scalp. They reflect neuronal activity in the auditory nerve, cochlear nucleus, superior olive, and inferior colliculus of the brainstem. They typically have a response latency of no more than six milliseconds with an amplitude of approximately one milli volt.
Due to their small amplitude, 500 or more repetitions of the auditory stimulus are required in order to average out the random background electrical activity. Although it is possible to obtain a BAEP to a pure tone stimulus in the hearing range a more effective auditory stimulus contains a range of frequencies in the form of a short sharp click.
Auditory Steady state Responses
The auditory steady state response (ASSR) is an auditory evoked potential (AEP) that can be used to objectively estimate hearing sensitivity in individuals with normal hearing sensitivity and with various degrees and configurations of sensorineural hearing loss (SNHL). The results obtained from ASSR testing can be used to estimate the behavioral pure-tone audiogram. This information is essential in the management of children with hearing loss. The person being tested must be very quiet and still in order to obtain reliable ASSR results. Often, testing is performed under sedation or in natural sleep for babies. Results are obtained by measuring brain activity while the person listens to tones of varying frequency (pitch) and intensity (loudness).
Some tests are carried out exclusively for the pediatric population. These include:
Visual Reinforcement Audiometry
Visual reinforcement audiometry (VRA) is based on the principle that when a child hears a sound, he or she will look to see what that sound was. VRA testing may be performed using earphones or in sound field. When performing VRA techniques, a specialized test room is equipped with toys situated to either side of the child, at about 90 degrees to the right and left. These toys are typically housed inside a dark plastic box and cannot be seen until they are activated by the tester. Upon activation the toy will light up and move inside its box. The tester, located outside the test room, has control of both the auditory signals and the visual reinforcement. The idea is for the child to associate the light-up toy with the sound they are hearing. Once the child is conditioned to look towards the sound, the intensity level of the stimuli will be reduced in increments until a threshold or minimum response level is obtained. The testing will then continue with another frequency tone or in the other ear.
Behavioral Observation Audiometry
Behavioural Observation Audiometry (BOA) involves presenting sounds to a baby and observing their responses and is appropriate from birth through age 7 months. The infant is observed for changes in behavior after presentation of an acoustic stimulus in the sound field. The child's responses may consist of quieting, eye widening, startle, changes in sucking ,etc.
Conditioned Play Audiometry
This method is appropriate for testing children from 30 months through 5 years of age. It is a listening game that uses toys to maintain the child's attention and focus to the listening task. The child is conditioned to perform a play activity (i.e., dropping a block in a bucket) whenever he or she hears a sound. Once the child is conditioned, threshold of hearing can be determined by decreasing signal intensity. Speech reception threshold, or SRT, testing may also be completedWhen the child hears the sound, they drop the block in a bucket. This is no different than raising one's hand in response to the sound, but the toys establish and maintains the child interested in the listening task for much longer than hand-raising alone. This "listening game" is demonstrated to the child by the audiologist, and once the child understands the game testing is underway.
All the above mentioned tests help to identify the type and degree of hearing loss. Once completed, test results and diagnosis are reported and uploaded in the electronic hospital records of each client which makes it is possible to track the progress of hearing loss, assess the outcome of medical treatment, hearing conservation and so on. We also counsel patients regarding their findings, the need for rehabilitation and follow-up.