The Threshold of the Stapedius Reflex for Pure Tone and Noise Stimuli

The Zwislocki acoustic bridge was used to study the acoustic stapedius reflex in 30 normal young adults. The stimuli were bursts of white noise, narrow bands of noise centered at 2 000 and 4 000 Hz, and pure tones of 250, 2 000 and 4 000 Hz. An electroacoustic data recording system was substituted for the aural monitoring system that is normally used with the Zwislocki bridge; the sensitivity of the system was such that it allowed identification of one to two decibel changes in the probe tone level. The mean threshold values for the pure tones studied were 81 dB SL, while the means associated with the several noise stimuli were 62 dB SL. The thresholds for the noise stimuli were found to be significantly more stable than those for pure tones.