Tests to estimate hearing ability can be performed on patients of any age (e.g., at birth before discharge from a hospital or birthing center, as part of a school screening program, or as adults if indicated). Hearing loss audiometry includes quantitative testing for a hearing deficit. An audiometer is used to measure and record thresholds of hearing by air conduction and bone conduction tests. The test results determine if hearing loss is conductive, sensorineural, or a combination of both. An elevated air-conduction threshold with a normal bone-conduction threshold indicates a conductive hearing loss. An equally elevated threshold for both air and bone conduction indicates a sensorineural hearing loss. An elevated threshold of air conduction that is greater than an elevated threshold of bone conduction indicates a composite of both types of hearing loss. A conductive hearing loss is caused by an abnormality in the external auditory canal or middle ear, and a sensorineural hearing loss by an abnormality in the inner ear or of the VIII (auditory) nerve. Sensorineural hearing loss can be further differentiated clinically by sensory (cochlear) or neural (VIII nerve) lesions. Sensorineural hearing loss is permanent. Additional information for comparing and differentiating between conductive and sensorineural hearing loss can be obtained from hearing loss tuning fork tests. Every state and territory in the United States has a newborn screening program that includes early hearing loss detection and intervention (EHDI). The goal of EHDI is to assure that permanent hearing loss is identified before 3 mo of age, appropriate and timely intervention services are provided before 6 mo of age, families of infants with hearing loss receive culturally competent support, and tracking and data management systems for newborn hearing screens are linked with other relevant public health information systems.