Biomedical subjects

D R Begault

Publications and source records attributed to D R Begault.

8 recordsLinked to original sources

PubMed2001

Direct comparison of the impact of head tracking, reverberation, and individualized head-related transfer functions on the spatial perception of a virtual speech source.

A study of sound localization performance was conducted using headphone-delivered virtual speech stimuli, rendered via HRTF-based acoustic auralization software and hardware, and blocked-meatus HRTF measurements. The independent variables were chosen to evaluate commonly held assumptions in the literature regarding improved localization: inclusion of head tracking, individualized HRTFs, and early and diffuse reflections. Significant effects were found for azimuth and elevation error, reversal rates, and externalization.

Acoustics↗

PubMed1998

Survey of commercial airline pilots' hearing loss.

64 commercial airline pilots (ages 35-64 yr, Mdn: 53) were surveyed regarding hearing loss and tinnitus. Within specific age groups, the proportions responding positively exceed the corresponding proportions in the general population reported by the National Center for Health Statistics.

Adult↗

PubMed1998

Virtual acoustics, aeronautics, and communications.

An optimal approach to auditory display design for commercial aircraft would utilize both spatialized (3-D) audio techniques and active noise cancellation for safer operations. Results from several aircraft simulator studies conducted at NASA Ames Research Center are reviewed, including Traffic alert and Collision Avoidance System (TCAS) warnings, spoken orientation "beacons" for gate identification and collision avoidance on the ground, and hardware for improved speech intelligibility. The implications of hearing loss among pilots is also considered.

Acoustics↗

PubMed1996

Three-dimensional audio versus head-down traffic alert and collision avoidance system displays.

The advantage of a head-up auditory display for situational awareness was evaluated in an experiment designed to measure and compare the acquisition time for capturing visual targets under two conditions: standard head-down Traffic Alert and Collision Avoidance System display and three-dimensional (3-D) audio Traffic Alert and Collision Avoidance System presentation. (The technology used for 3-D audio presentation allows a stereo headphone user to potentially localize a sound at any externalized position in 3-D auditory space). Ten commercial airline crews were tested under full-mission simulation conditions at the NASA-Ames Crew-Vehicle Systems Research Facility Advanced Concepts Flight Simulator. Scenario software generated targets corresponding to aircraft that activated a 3-D aural advisory (the head-up auditory condition) or a standard, visual-audio TCAS advisory (map display with monaural audio alert). Results showed a significant difference in target acquisition time between the two conditions, favoring the 3-D audio Traffic Alert and Collision Avoidance System condition by 500 ms.

Accidents, Aviation↗

PubMed1994

Multichannel spatial auditory display for speech communications.

A spatial auditory display for multiple speech communications was developed at NASA/Ames Research Center. Input is spatialized by the use of simplified head-related transfer functions, adapted for FIR filtering on Motorola 56001 digital signal processors. Hardware and firmware design implementations are overviewed for the initial prototype developed for NASA-Kennedy Space Center. An adaptive staircase method was used to determine intelligibility levels of four-letter call signs used by launch personnel at NASA against diotic speech babble. Spatial positions at 30 degrees azimuth increments were evaluated. The results from eight subjects showed a maximum intelligibility improvement of about 6-7 dB when the signal was spatialized to 60 or 90 degrees azimuth positions.

Auditory Perception↗

PubMed1993

Headphone localization of speech.

Three-dimensional acoustic display systems have recently been developed that synthesize virtual sound sources over headphones based on filtering by head-related transfer functions (HRTFs), the direction-dependent spectral changes caused primarily by the pinnae. In this study 11 inexperienced subjects judged the apparent spatial location of headphone-presented speech stimuli filtered with non-individualized HRTFs. About half of the subjects "pulled" their judgments toward either the median or the lateral-vertical planes, and estimates were almost always elevated. Individual differences were pronounced for the distance judgments; 15% to 46% of stimuli were heard inside the head, with the shortest estimates near the median plane. The results suggest that most listeners can obtain useful azimuth information from speech stimuli filtered by nonindividualized HRTFs. Measurements of localization error and reversal rates are comparable with a previous study that used broadband noise stimuli.

Adult↗

PubMed1993

Head-up auditory displays for traffic collision avoidance system advisories: a preliminary investigation.

The advantage of a head-up auditory display was evaluated in a preliminary experiment designed to measure and compare the acquisition time for capturing visual targets under two auditory conditions: standard one-earpiece presentation and two-earpiece three-dimensional (3D) audio presentation. Twelve commercial airline crews were tested under full mission simulation conditions at the NASA-Ames Man-Vehicle Systems Research Facility advanced concepts flight simulator. Scenario software generated visual targets corresponding to aircraft that would activate a traffic collision avoidance system (TCAS) aural advisory; the spatial auditory position was linked to the visual position with 3D audio presentation. Results showed that crew members using a 3D auditory display acquired targets approximately 2.2 s faster than did crew members who used one-earpiece headsets, but there was no significant difference in the number of targets acquired.

Accidents, Aviation↗

PubMed1991

Preferred sound intensity increase for sensation of half distance.

Two experiments are reported that examine the preferred increase in intensity for creating a percept of half auditory distance from a reference. The results of both experiments indicate that the use of an inverse square law (increments of 6 dB) is not the best signal-processing method for this purpose. The application of the results is potentially useful towards the software design of 3-D auditory display systems that manipulate the perceived distance of auditory inputs in relationships to actual distances of physical objects.

Adult↗