Thyroid hormone plays an important role in hearing development The exact incidence of hearing impairment in untreated congenital hypothyroid newborns (CH) is unknown. This paper presents the results of the measuring of the transient-evoked otoacoustic emissions (TEOAE) on a population of 29 newborns positive to the screening test for hypothyroidism. TEOAE were recorded in all newborns in 1 month after birth and before starting the L-thyroxin treatment. We performed both temporal and time-frequency analysis of the responses by means of wavelet transform 68 newborns who had no risk factor for hearing loss served as control. The comparison of the characteristics of temporal and frequency content of the responses of the two groups showed no statistically significant difference (p=0.01).