The effects of audibility and age on masking for sentences in continuous and interrupted noise were examined in listeners with real and simulated hearing loss. The absolute thresholds of each of ten listeners with sensorineural hearing loss were simulated in normal-hearing listeners through a combination of spectrally-shaped threshold noise and multi-band expansion for octave bands with center frequencies from 0.25-8 kHz. Each individual hearing loss was simulated in two groups of three normal-hearing listeners ͑an age-matched and a non-age-matched group͒. The speech-to-noise ratio ͑S/N͒ for 50%-correct identification of hearing in noise test ͑HINT͒ sentences was measured in backgrounds of continuous and temporally-modulated ͑10 Hz square-wave͒ noise at two overall levels for unprocessed speech and for speech that was amplified with the NAL-RP prescription. The S/N in both continuous and interrupted noise of the hearing-impaired listeners was relatively well-simulated in both groups of normal-hearing listeners. Thus, release from masking ͑the difference in S/N obtained in continuous versus interrupted noise͒ appears to be determined primarily by audibility. Minimal age effects were observed in this small sample. Observed values of masking release were compared to predictions derived from intelligibility curves generated using the extended speech intelligibility index ͑ESII͒ ͓Rhebergen et al. ͑2006͒. J. Acoust. Soc. Am. 120, 3988-3997͔.

This work is aimed at developing a design for the use of a microphone array with binaural hearing aids. The goal of such a hearing aid is to provide both the spatial-filtering benefits of the array and the natural benefits to sound localization and speech intelligibility that accrue from binaural listening. The present study examines two types of designs for fixed-processing systems: one in which independent arrays provide outputs to the two ears, and another in which the binaural outputs are derived from a single array. For the latter, various methods are used to merge array processing with binaural listening. In one approach, filters are designed to satisfy a frequency-dependent trade between directionality and binaural cue fidelity. In another, the microphone signals are filtered into low-and high-frequency components with the lowpass signals providing binaural cues and the highpass signal being the single output of the array processor. Acoustic and behavioral measurements were made in an anechoic chamber and in a moderately reverberant room to evaluate example systems. Theoretical performance was calculated for model arrays mounted on an idealized spherical head. Results show that both single-and dual-array systems provided targetintelligibility enhancements (2-4 dB improvements in speech reception threshold) relative to binaural cardioid microphones. In addition, the binaural-output systems provided cues that assist in sound localization, with resulting performance depending directly upon the cue fidelity. Finally, the sphere-based calculations accurately reflected the major features of the actual head-mounted array results, both in terms of directional sensitivity and output binaural cues.

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An approach to hearing aid design is described, and preliminary acoustical and perceptual measurements are reported, in which an acoustic beam-forming microphone array is coupled to an eye-glasses-mounted eye-tracker. This visually guided hearing aid (VGHA)—currently a laboratory-based prototype—senses direction of gaze using the eye tracker and an interface converts those values into control signals that steer the acoustic beam accordingly. Preliminary speech intelligibility measurements with noise and speech maskers revealed near- or better-than normal spatial release from masking with the VGHA. Although not yet a wearable prosthesis, the principle underlying the device is supported by these findings.

BlindAid is a virtual environment (VE) system that enables blind people to more easily learn about new environments on their own. The system is implemented on a desktop personal computer with a Phantom  haptic interface and three-dimensional spatialized audio. In addition to providing blind users with non-visual stimuli similar to what they will depend on in the actual environment, the system is designed to enhance and accelerate the user's understanding of the unknown environment by giving him/her the ability to interact with the VE in ways that are not possible in the real world. The BlindAid system was developed and evaluated as part of an experimental study related to how people who are blind build cognitive maps of their physical environment and how recent advances in VE technology might support orientation and mobility (O&M) training. The current system is able to provide a visual display and record the user's actions in the VE for later review by researchers and O&M instructors. The paper focuses on the technical development of the system with some results from an initial evaluation by four blind volunteers.