Audiological Assessment

Pure Tone Audiometry (PTA): This is a subjective test performed in older children and adults, which involves the use of single frequency tones, also known as ‘pure tones’ that are transmitted either through the air or bone conduction pathways across various frequencies. Upon hearing the tone, test subjects are required to respond by raising their hand or pressing the response button. The audiologist continues to vary the intensity in order to determine the lowest sound level (known as the audiometric threshold for that particular frequency) at which the patient responds at least 50% of the time. After obtaining the thresholds for all the frequencies, the audiologist proceeds to plot an audiogram which measures the type and severity of hearing loss.

Speech Audiometry: This is a subjective test performed in older children and adults, which helps identify a majority of problems that result in hearing loss. The test involves checking the patient’s ability to distinguish and repeat speech stimuli at different sound intensities. 

Acoustic Immittance Testing: This is an objective test performed in individuals of all age groups, that evaluates the function of the tympanic membrane and the muscle reflexes surrounding it. Moreover, it also helps localize the site of lesion. It is an umbrella term that includes tests such as tympanometry or impedance audiometery and Acoustic Reflex Threshold (ART). Tympanometry is a measurement of the tympanic membrane (eardrum) and middle ear function that helps determine the presence of tumours, perforations or a buildup of fluid or ear wax. By varying pressure in the ear canal, the response (mobility) of the tympanic membrane to this sound at different levels is measured. The Acoustic Reflex Threshold (ART) on the other hand, is used to determine the type and location of your hearing problem (the ossicles, cochlea, auditory nerve, etc). The test involves the evaluation of involuntary muscle contractions in the middle ear. Ipsilateral and contralateral evaluation of acoustic reflexes is performed to assess the integrity of the acoustic reflex pathway. 

Otoacoustic Emissions (OAE): This is an objective screening and diagnostic test that helps measure the cochlear hair cell function, particularly the outer ones. OAEs are sounds generated by the cochlea in response to auditory (acoustic) stimuli. The absence of OAEs may signal hearing loss a possible blockage in the outer or middle ear. 

Brainstem Evoked Response Audiometry (BERA): Also known as Auditory Brainstem Response (ABR), this is an objective test used to assess the estimation of hearing sensitivity, neural integrity and synchrony. It is a non-invasive procedure that involves placing electrodes on the mastoid and forehead and administering sound stimuli such as clicks through inserted earphones. These help detect the electrical stimulation activity from the auditory nerve to the inferior colliculus. In order to avoid picking up false stimuli, the patient is required to remain as quiet and still as possible throughout the test.

Visual Reinforcement Audiometry (VRA): This is a subjective test conducted among infants and toddlers as young as five months of age. It involves the use of a conditioned localization response and visual reinforcement to measure hearing. It is recommended for babies up to 24 months of age and typically involves two phases: the conditioning phase, where baby is conditioned to respond to the sound by looking at the visual reinforcer, and the testing phase, where an actual threshold is considered once the baby is conditioned.

Tangible Reinforcement Operant Conditioning Audiometry (TROCA): This is a subjective test that is used among children in the 2-4 year age group, particularly those with developmental difficulties. The test involves assessing the child’s response to a tone, either by pushing a button or through any other simple motor response. A tangible reinforcement is provided after each response to encourage the child.

Condition Play Audiometry (CPA): This is a subjective test typically used for preschool between the ages of 2 and 5 years. CPA is a fun test involving the use of toys to direct the child’s attention on the listening task, eventually turning it into a game. The first part of the task is to condition the child by allowing him/her to drop the ball into the bucket each time they hear the sound. Once comfortable, the testing phase is initiated, where the actual thresholds of the child are considered. 

Other subjective special tests for differential diagnosis: These include Short Increment Sensitivity Index (SISI) test and the Speech Perception in Noise (SPIN) test. The former checks for recruitment — a condition caused by damage to the cochlear hair cells that changes the perception of small increments in sound, causing them to be perceived at much more exaggerated levels. The latter on the other hand, evaluates how well an individual can comprehend speech in the presence of background noise.