Types of Hearing Test
No child is too young for a hearing test! Infants are now routinely screened for potential hearing loss before they leave the hospital. The type of test used to assess a child’s hearing status depends on the age and cognitive function of the child. Infants are tested in two ways: behaviorally and/or electrophysiologically.
Behavioral observation assessment (BOA) testing is conducted by an audiologist specially trained to detect bodily reactions to sound i.e. cessation of activity, body movement, eye widening, eye opening, or change in sucking rate.
The Auditory Brainstem Response (ABR)
As children mature, so does their ability to respond to sound. At approximately six to seven months of age, normally-developing children are able to turn toward a sound source. Children at this level are tested either using earphones or in the sound booth without earphones but using speakers. Sounds used for testing typically include low pitch to high pitch tones that are included in the speech range. Turning toward the sound source is reinforced with a lighted toy. This type of testing is called visual reinforcement audiometry (VRA) and is generally quite accurate in determining hearing levels.
By approximately 2 1/2 – 3 years of age most children can be tested using a technique called conditioned play audiometry. Earphones are placed on the child and she/he is conditioned to play various games when the test tone is heard.
Traditional or standard audiometry is used with older children and adults. This method requires the patient to press a response button or raise a hand when the test test tone is heard.
Basic audiogram : This test determines the patient’s hearing ability relative to normal adult hearing levels to determine if there is a hearing loss, where it occurs and its type or classification. This information is critical to determine if medical or surgical intervention is possible or if hearing aids may help. Enhanced communication strategies may also be discussed during this session.
Special tests :
Tympanometry or acoustic immittance testing is often an integral part of the test battery. This test is used to assess the status of the middle ear and related structures. Tympanometry measures the movement of the ear drum (tympanic membrane). This information is used in the diagnosis of middle ear disease or other problems that might restrict ear drum movement.
Acoustic reflexes are measured in order to determine whether the middle ear muscles are properly reacting to loud sounds. This test can also be used to assist in testing of hearing in young children and/or to identify other otologic problems.
Auditory Brainstem Response Audiometry (ABR), or Brainstem Auditory Evoked Response (BAER), is an objective procedure used to measure the function of the brainstem in response to sound. The results can provide general information regarding hearing sensitivity. This test can also be used for neuro-diagnostic purposes, to determine if the brainstem is transmitting sound properly. A series of clicks or tones are presented to the patient while she/he rests or sleeps. Electrodes are placed on the head to detect the response of the brainstem to the sounds; the electrodes do not cause any pain or discomfort.
Bone Conduction BERA : With BC ABR we can also test patients with congential External and Middle malformations. Additional use of BC BERA with AC BERA can also indicate type of Hearing loss. This test not only confirm a conductive loss but also helps to calculate the amount of hearing loss due to the conductive component.
Electro Cochleography (EcochG) : Electrocochleography is used to diagnose Meniere’s Disease.We use non invasive gold plated tiptrodes.
Otoacoustic Emissions (OAEs : DPOAEs & TEOAEs) – Otoacoustic emissions (OAE) are inaudible sounds emitted by the cochlea when the cochlea is stimulated by a sound. When sound stimulates the cochles, the outer hair cells vibrate. The vibration produces an inaudible sound that echoes back into the middle ear. The sound can be measured with a small probe insertedinto the ear canal. Persons with normal hearing produce emissions. Those with hearing loss greater than 25-30 db does not emitted. OAEs can detect blockage in the outer ear canal,middle ear fluid, and damage to the outer hair cells in the cochlea.
Auditory Steady State Evoked Potentials (SSEPs) : Latest technology for hearing assessment of an infant as old as 7 day. Results are in the form of automated audiograms generated by the special software.