Acoustic reflex patterns according to different intensity and different duration of white noise (WN) stimuli.

The data were gathered by connecting the output from a middle ear impedance meter (Amplaid 702) to the computer and averaging section of the Amplaid MK VI which was also used as an acoustic stimuli generator. The stimuli consisted of white noise bursts having different peak equivalent sound pressures (115, 105, 95, 85 dB SPL) and different durations (from 1000 to 3 msec). The parameters examined were: stapedius muscle contraction latency time; muscle fibre recruitment time, i.e. the interval between the onset of contraction and its maximum; duration of contraction; amplitude of maximum contraction. An evaluation was also made as to the "efficiency" of contraction, expressed as the function of duration and amplitude. The authors discuss the different patterns of "efficiency" curve achieved at various intensity levels by stimuli of different duration.