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Fig. 4. Auditory Localization Facility (ALF), circa 2004.
in Fig. 4. This facility enabled fast and accurate collection of head-related transfer functions (HRTFs) which were impor- tant to synthetic 3-D audio displays. Additionally, the ALF was used to compare human localization performance in a real environment with the synthetic spatial auditory display environment. At this time, AFRL also expanded their research efforts investigating the effects of electronic noise and radio interference on speech intelligibility, where both the talker and listener were in operationally relevant high lev- els (>100 dB) of broadband, ambient, acoustic noise.
In the 1990’s, AFRL collaborated with the US Navy/US Marine Corps and NASA to conduct flight tests of 3-D audio displays on a Navy/Marine Corps AV-8B Harrier and a NASA Glenn Research Center OV-10 Bronco. These were the world’s first flight tests of a synthetic 3-D audio system.5 Basic research was initiated investigating the effect of spa- tial auditory cures on aurally-guided visual search. The ini- tial experiments demonstrated that the human auditory system was very effectively guiding the visual gaze of the subject. The results showed a decreased reaction time in locating and discriminating a small (<1°) target from 30 seconds without the spatial auditory cue to 1.5 – 2 seconds with spatial auditory cueing. The results were also depend- ent on the visual field of view, with smaller, more restricted field of views receiving a larger benefit from the addition of spatial auditory cueing. During the 1990’s, AFRL also col-
laborated with the US Navy to conduct measurements of flight deck operational noise on US Navy aircraft carriers. The results of these noise measurements showed noise lev- els from 130-148 dB and brought a new focus to developing new hearing protection devices with improved noise atten- uation and new programs in hearing protection research that included investigations of the potential impacts of bone conducted noise.
Current efforts
The new millennium brought exciting and challenging projects run by an excellent cadre of scientists and engineers using world-class acoustics facilities and instrumentation. The multi-disciplinary researchers include experts in audiology, biomedical engineering, human factors engineering, human factors psychology, mechanical engineering, physics, and speech and hearing science. This team is focused on research- ing the fundamental underpinnings of human auditory per- ception of simple and complex sound (including speech) and the effects of noise to optimize the design of auditory inter- faces, acoustic models, and communication technologies. The laboratory also hosts visiting scientists. National Research Council (NRC) post-doctoral fellows and laboratory person- nel mentor and host undergraduate and graduate students in science and engineering. Additional collaborations are facili- tated via educational partnership agreements, cooperative
24 Acoustics Today, January 2010