The effect of masking on the acoustic reflex threshold
This study investigated the effect of masking noise on the threshold for s tape dial reflex. It has been shown that masking which shifts the hearing threshold causes a loudness function typical of recruitment. It was hypothesized that the stapedial reflex threshold remains the same in a masked situation as in the unmasked situation. It was suggested that this demonstrates recruitment in that the presence of noise reduces the range between hearing thresholds and stapedial reflex thresholds. Ten subjects, with no known hearing loss or pathology involving the ear or reflex arc were used in this study. A 1000 Hz tone was used as the pure tone stimulus and narrow band noise centered at 1000 Hz was used as the masking stimulus. Pure tone thresholds were obtained without masking. The amount of masking necessary to shift the pure tone threshold. 30 dB was then found. Stapedial reflex thresholds were found without masking and in the presence of the masking stimulus at the intensity required to shift the hearing threshold 30 dB. The differences in stapedial reflex thresholds obtained with masking and without masking were evaluated for significance, as were the differences in intensity above hearing threshold in each case needed to elicit the stapedial reflex. It was found that there was no significant difference in the stapedial reflex thresholds when those obtained without masking were compared with those obtained in the presence of masking. There was a significant reduction in intensity above hearing threshold at which stapedial reflex occurred when the results in the masked situation were compared with those obtained in the unmasked situation. It was concluded that the stapedial reflex threshold is not affected by the 30 dB effective masking used in this study, but that this masking stimulus can be applied to simulate a sensori-neural hearing loss and recruitment in the study of stapedial reflex thresholds.