Programs that offer hearing threshold tests for the purpose of identifying individuals whose ability to perceive sound falls outside the normal range. People who fail the screening test need an in-depth evaluation by an audiologist.

Programs that establish the nature and extent of an individual's hearing loss in order to devise an appropriate treatment plan. Evaluations may include pure tone and speech audiometry which measure hearing in terms of reception of calibrated test tones or spoken words which are presented at controlled levels of intensity; impedence tests which measure the integrity of the middle ear system and rule out conductive pathology; and auditory brain stem tests which utilize equipment similar to an EKG to measure neurological activity in response to auditory stimuli.

A disruption in the normal hearing process that may occur in the outer, middle, or inner ear, which prevents sound waves from being converted to electrical signals and nerve impulses from being transmitted to the brain to be interpreted. Included are conductive hearing loss that results from abnormalities of the external ear and/or the ossicles of the middle ear; sensorineural hearing loss that results from malfunction of inner ear structures (i.e., cochlea); and central auditory dysfunction that results from damage or dysfunction at the level of the eighth cranial nerve, auditory brain stem, or cerebral cortex. Hearing loss may be present at birth (congenital) or become evident later in life (acquired); and may or may not preclude the normal development of language. The severity of hearing loss is measured in decibles (dB). The threshold or 0 dB mark for each frequency refers to the level at which typical young adults perceive a tone burst 50% of the time. Hearing is considered normal if an individual's thresholds are within 15 dB of normal thresholds. Severity of hearing loss is graded as mild (26-40 dB), moderate (41-55 dB), moderately severe (56-70 dB), severe (71-90 dB) and profound (90 dB).