The effect of ear-canal air pressure on click-evoked otoacoustic emissions was measured for pressures ranging from 200 to -200 daPa and stimulus levels ranging from 60-90 dB PeSPL. Positive and negative ear-canal pressures (relative to ambient pressure) reduced the emission amplitude by 3-6 dB. A spectral analysis of the emissions revealed that the effect of ear-canal air pressure is that of a high-pass filter with a cutoff frequency of 2600 Hz and a slope of 4 dB/oct. The spectral changes are the expected effect of an increase in stiffness of the middle ear and were independent of pressure polarity and click level. Ear-canal air pressure substantially reduced the reproducibility of the emission waveform, in many cases rendering the emission indistinguishable from background noise. The implication of these findings for hearing screening applications is that a high false alarm rate may occur in normal-hearing patients with intratympanic air pressures that are significantly different from ambient pressure.

Hearing adults produced signed and spoken monologues under conditions of quiet or 80 dB SPL of noise and with their vision unobstructed or obstructed. Their signs were videotaped and a random sample of 24 frames was analyzed in each condition through a computer program that determined the overall distance of the hand from a marker placed on the signer's torso. Vocal intensity was digitized from the tape recordings and analyzed by computer for 1 min of continuous speech in each condition. The visual obstruction had no effect either on the distance of the signs or on the vocal intensity of their speech. The subjects increased vocal intensity by about 55% when the noise was introduced (the usual Lombard effect), but the noise had no effect on the distance of the signs. Sign performance was not influenced by visual feedback, and sign and speech were independent communication systems, even in bilingual speaking and signing subjects.

This study investigated the effects of reduced visibility on the distance of signing hands from the bodies of adult signers who are deaf and on their rates of sign production. Subjects were videotaped as they signed with partners in each of three experimental conditions: unimpeded, moderately impeded, and severely impeded visibility. Visual impedance was created by placing screens between signing partners. The distance of a hand from the body, in terms of lateral, vertical, and forward-depth dimensions, was determined from digitized measurements of single video frames randomly selected from those in which the subject was actively signing. Sign rate was calculated as the number of signs produced in a given segment of time. Signs produced in the severely impeded visibility condition were found to be made at a slower rate and with a mean hand position further forward and vertically higher than signs produced in the unimpeded visibility condition.