Detectability of the acoustically evoked composite response (40 HZ potential) near threshold

In 56 persons with normal hearing and 10 patients with sensorineural hearing loss, acoustically evoked potentials were recorded at stimulus repetition rates of 10/s, 20/s, 30/s and 40/s. With a sufficiently low lower amplifier cut-off frequency, one obtains at the repetition rate of 40/s a composite response described by Galambos et al. (1981) as 40 Hz potential, which consists of the ABR evoked by the given stimulus and superposed MLR-waves evoked by the preceding stimuli. In both groups the amplitude mean value of the potentials recorded at the stimulus rate 40/s was significantly higher than at lower rates. The detectability of the near-threshold response for the subjects with normal hearing was distinctly higher than the responses recorded at lower rates.