Pure Tone Audiometry (PTA) makes use of single frequency tones or “pure tones” given via air and bone conduction pathways, across a range of frequencies. Every time the subject hears the test tone, they are required to respond by raising their hand or pressing the response button. The intensity of the tone is varied until the audiologist can determine the lowest sound level at which the patient responds at least 50% of the time. This level is known as the audiometric threshold for that particular frequency. Once the thresholds for all the frequencies are obtained, the audiogram can be plotted, which gives information about the type and severity of hearing loss.
Speech Audiometry checks the patient’s ability to identify and repeat speech stimuli at different sound intensities. The results of these tests in conjunction can identify majority of the problems related to the cause of hearing loss.
Tympanometry or Impedance Audiometry assesses the middle ear functioning by varying the pressure in the ear canal. It can determine if there is a buildup of fluid, wax buildup, eardrum perforations or tumors.
Acoustic Reflex Testing measures involuntary muscle contractions of the middle ear and is used to determine the location of your hearing problem (the ossicles, cochlea, auditory nerve, etc.) as well as the type of hearing loss.
Otoacoustic Emissions (OAE) is an objective test that can be used for screening as well as diagnostic purpose across all age ranges. OAE tests the functioning of the cochlear hair cells, specifically the outer hair cells, in response to acoustic stimuli.
Brainstem Evoked Response Audiometry (BERA) is an objective test.It is a non-invasive procedure that uses electrodes placed on the mastoid and forehead areas to detect electrical activity from the auditory nerve to the inferior colliculus. For both this procedure , the subject is required to remain quiet and as still as possible in order to avoid picking up false responses, known as artifacts.
Other subjective special tests for differential diagnosis include Short Increment Sensitivity Index (SISI) test that checks for recruitment (which is a condition in which small increments in sound are perceived at an exaggerated level, caused due to damage to the cochlear hair cells, which are otherwise not noticeable by normal ears), and Speech Perception in Noise (SPIN) to know how well an individual can understand speech in the presence of background noise.