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Pure tone eudiometry (PTA) is one of the key hearing test used to identify hearing threshold levels of an individual. It helps us in determining the degree, type and configuration of a hearing loss. Patient is asked to respond to the pure tone stimuli presented at different frequencies & hence PTA is a subjective, behavioral measurement of one’s hearing threshold. As such PTA is administered on adults and children old enough to cooperate with the test procedure. PTA is performed in sound treated rooms with calibrated audiometers by a professional Audiologist. Both Air conduction & bone conduction thresholds are detected by this test.
Immitance audiometry is a test in which one’s middle ear is analyzed. It is a very quick, simple, reliable and relatively objective method of determining one’s middle-ear function, detecting the presence of middle ear fluid or ear drum perforation etc. Acoustic-immitance measurements provide sophisticated data that give us valuable information concerning the middle ear mechanism as a whole.
Speech Audiometry coupled with PTA testing provides more credible results for determining the patient’s hearing and communication status as it helps to ascertain the patient’s ability to understand speech.
With the help of Speech Audiometry, we determine the threshold of speech which is the lowest level at which speech is audible or intelligible. The lowest level at which the speech signal can be heard 50 percent of the time is the speech /detection threshold (SDT) or Speech Awareness Threshold (SAT).
Another undermining factor is the SRT or the speech recognition threshold which is the lowest level at which a speech signal is intelligible enough to be recognized 50 percent of the time. The SRT is usually obtained by asking the patient to repeat the spondee words (Bi syllabic words with equal emphasis on both the syllables).
Otto acoustic emission test helps us to assess the functioning of the hair cells in the cochlea. OAE test is a simple, quick and non-invasive test, for detecting hearing defects in newborn babies and in children who are too young to cooperate with the conventional hearing tests. It is considered as the test for the universal new born hearing screening program. Periodic early childhood hearing screening programs are also conducted incorporating OAE technology.
The brainstem evoked response audiometry (BERA) is an objective neurophysiologic method for evaluating hearing threshold and diagnosing retro cochlear lesions.
In a BERA test, brain stem potentials (as wave forms) are elicited in response to audio logical click stimuli. These waves are recorded by electrodes placed over the scalp of an individual.
BERA test is an effective tool for assessing hearing thresholds of difficult to test population like new born, children, bed ridden patients, mentally challenged patients, patients with behavioral problems etc.