Effect of crossed stapedius reflex on vibration of mallear handle in man.

The ear drum was made to vibrate using frequency-modulated sound pulses of 40 ms duration, and the vibration velocity of the tip of the mallear handle (umbo) was measured with laser vibrometry before and during stapedius muscle contractions (elicited by sound of 100 dB HL in the contralateral ear). The stapedius reflex caused: an attenuation of the mallear vibrations below 1 kHz, a slight enhancement of the vibrations between 300 Hz and 1,500 Hz. These effects of the stapedius reflex appear to be caused by an increased stiffness in the structures affecting the mallear vibrations.