Fourier analysis in the objectivisation of auditory brain stem responses in newborns.

Fourier analysis (FFT) of auditory brain stem responses induced by stimuli of 90, 70 and 40 dB HL was carried out in group of 45 full-term and pre-term neonates. It was stated that with postnatal newborn's development complex IV/V was observed more frequently for the more immature newborn. It influences also the power strength spectrum obtained. In responses with IV/V complex the frequency range is considerable and significantly reduced by about 100-200 Hz. It was observed that general state of newborn at the birth influences the frequency range as well as from the shape of score reproducibility and reliability of spectrum is significantly better. It was noticed also that the shape and form of spectrum in about threshold and threshold responses is significantly similar irrespective of the intensity of threshold stimulus. The shape and form of responses spectra for stimuli of 30-40 dB HL (in a group of children with normal hearing) and of 80-90 dB HL (in a group of children with severe hearing impairment) are identical. The above findings allow us to show the importance of Fourier analysis for objectivisation of subjective evaluation of auditory brain stem responses.