Transcranial conduction of acoustic-reflex-eliciting signals.

Conduction of a broad-band signal from a supra-aural earphone to an acoustic-immittance instrument coupled to the contralateral ear canal was studied using three commercial immittance instruments. Results indicated that portions of the broad-band signal reached the contralateral ear canal at presentation levels of 100-110 dB SPL. At levels as low as 100 dB SPL, the signal was detected by at least one of the acoustic-immittance instruments. At higher sound pressure levels the transmitted signal caused deflections of the acoustic-immittance meter similar to those associated with an acoustic-reflex response. However, these artifacts could be differentiated from acoustic-reflex responses in several respects and could be prevented by high-pass filtering of the broad-band test signal.