Abstract: Neonates are tested for hearing deficiencies. A printed record is made of changes in heart beat rate in response to various sound stimuli. Relevant information such as heart beat rate, frequency of the stimulating sound, intensity of the stimulating sound, and related clock information is printed out in digital form. In a modification, changes in time between heart beats are extrapolated so that, in effect, changes in heart beat rate may be quickly determined on a go-no-go basis. These tests are particularly useful on infants under the age of eight months so that corrective measures may be taken prior to expiration of a critical period of development in the infant's life.