An artifact in acoustic reflex measurement: some further observations

This study was designed to clarify characteristics of an artifact that has been reported to be a potential source of misleading information when determing acoustic reflex thresholds elicited by low-frequency tones. The study was conducted in two parts. Experiment 1 was concerned with an investigation of acoustic interactions in a sealed cavity between the probe tone from a commercial electroacoustic impedance bridge and interfering tones of various frequencies. Experiment 2 consisted of measurements of sound pressure levels in the sealed external ear canal of the probe ear when the contralateral ear was stimulated by air-conducted pure tones. The results indicated that acoustic reflex thresholds in 250-Hz tones probably cannot be determined for most persons unless special measures are taken to prevent the artifact. The artifact should not occur when the eliciting stimulus is 500 Hz, however.