Search

Objective: To design and develop a Portable Auditory Localization Acclimation Training (PALAT) system capable of producing psychoacoustically accurate localization cues; evaluate the training effect against a proven full-scale, laboratory-grade system under three listening conditions; and determine if the PALAT system is sensitive to differences among electronic level-dependent hearing protection devices (HPDs). Background: In-laboratory auditory localization training has demonstrated the ability to improve localization performance with the open (natural) ear, that is, unoccluded, and while wearing HPDs. The military requires a portable system capable of imparting similar training benefits as those demonstrated in laboratory experiments. Method: In a full-factorial repeated measures design experiment, 12 audiometrically normal participants completed localization training and testing using an identical, optimized training protocol on two training systems under three listening conditions (open ear, TEP-100, and ComTac™ III). Statistical tests were performed on mean absolute accuracy score and front-back reversal errors. Results: No statistical difference existed between the PALAT and laboratory-grade DRILCOM systems on two dependent localization accuracy measurements at all stages of training. In addition, the PALAT system detected the same localization performance differences among the three listening conditions. Conclusion: The PALAT system imparted similar training benefits as the DRILCOM system and was sensitive to HPD localization performance differences. Application: The user-operable PALAT system and optimized training protocol can be employed by the military, law enforcement, and various industries, to improve auditory localization performance in conditions where auditory situation awareness is critical to safety. [ABSTRACT FROM AUTHOR]

INTRODUCTION Driver fatigue is recognized as a major causal factor in accidents involving long-haul commercial drivers. The development of an on-board driver performance/fatigue monitoring system could potentially assist drivers in […], This on-road field investigation employed, for the first time, a completely automated trigger-based data collection system capable of evaluating driver performance in an extended-duration real-world commercial motor vehicle environment. The study examined the use of self-assessment of fatigue (Karolinska Sleepiness Scale) and temporal separation (minimum time to collision, minimum headway, and mean headway) as indicators of driver fatigue. Without exception, the correlation analyses for both the self-rating of alertness and temporal separation yielded models low in associative ability; neither metric was found to be a valid indicator of driver fatigue. In addition, based upon the data collected for this research, preliminary evidence suggests that driver fatigue onset within a real-world driving environment does not appear to follow the standard progression of events associated with the onset of fatigue within a simulated driving environment. Application of this research includes the development of an on-board driver performance/fatigue monitoring system that could potentially assist drivers in identifying the onset of fatigue.

INTRODUCTION In many work environments, the audibility of human speech, warning signals, and other auditory cues by workers is of the utmost importance, but the presence of noise in such […], An experiment was conducted wherein masked thresholds (using ascending method of limits) for a backup alarm were obtained in pink and red noise at 85 and 100 dBA for 12 participants immersed in a probability monitoring task and wearing a conventional passive hearing protection device (HPD, an earmuff or a foam earplug), an active noise reduction (ANR) headset, or no HPD at all (only in 85 dBA noise). Results revealed statistically significant between-HPD differences in red noise (from 2.3 to 3.1 dB) and in the 100-dBA noise level (from 2.6 to 4.3 dB). An additional finding, which corroborates other studies using different protocols, was that masked thresholds in 85-dBA noise were significantly lower (from 3.2 to 4.4 dB) for the occluded conditions (wearing an HPD) than for the open-ear (unoccluded) condition. This result refutes the belief among many normal-hearing workers that the use of HPDs in relatively low levels of noise compromises their ability to hear necessary workplace sounds. Actual or potential applications of this research include (a) the selection of appropriate HPDs for low-frequency-biased noise exposures wherein signal detection is important and (b) gaining insight into the appropriateness of ANR-based HPDs for certain industrial noise environments.

A factorial experiment was conducted to study the pulse parameters believed to have affected the perceived urgency and response time to auditory warning signals. Pulse format, pulse level and inter-pulse interval were considered as independent variables. Subjective perceived urgency was estimated using psycho-physical methods of free-modulus magnitude estimation and paired comparison. Response time substantially fell as perceived urgency rose according to multivariate statistical analyses done.

An experiment was conducted to compare both speech intelligibility and noise attenuation of a conventional passive headset (David Clark H10-76) and an electronic Active Noise Reduction (ANR) headset (Bose Aviation) operated with and without its ANR feature. Modified Rhyme Tests were conducted in pink and tank noise, and with and without bilateral phase reversal between earphones. The Bose ANR unit required a significantly higher speech-to-noise (S/N) ratio in both noise environments than the two passive headset systems to maintain equal intelligibility, in part because of its stronger noise reduction and higher required signal level. Articulation Index calculations corroborated the empirical result that the David Clark afforded comparable intelligibility to the Bose ANR device. Bilateral phase reversal proved to be of no benefit, and pink noise proved to be the harsher environment for speech intelligibility. On a speech intelligibility basis alone, the results do not justify the additional cost of the ANR headset; however, when severe noise exposure is at issue, a properly functioning ANR unit may afford more protection than a similar passive headset without electronics, especially in low-frequency noise spectra.

Objective: Design an optimised auditory azimuth localisation training protocol by: (1) differing the number of training stimuli presentations to determine the highest angular accuracy achieved in the fewest training sessions, (2) evaluating the presence of training transfer from a broadband stimulus to untrained military-relevant stimuli and (3) measuring the effect of differing training strategies on localisation accuracy. Design: Two pilot studies of 18 and six subjects, respectively, determined the number of presentations and type of stimuli to be included in a localisation training experiment that evaluated different training strategies. In the pilot studies, participants trained using eight Learning Units (LU) and then tested using untrained stimuli. In the main experiment, 40 participants completed eight LUs using four different learning strategies, with 10 participants randomly assigned to each condition. Sample: All participants were ages 18–42 normal-hearing listeners with thresholds not exceeding 25 dB HL and asymmetry not exceeding 15 dB HL. Results: Transfer of training occurred using three of the four untrained stimuli. The training strategy that resulted in the highest localisation accuracy involved active participation. Conclusions: Training with a broadband stimulus transfers to untrained broadband stimuli. Training involving the active participation strategy resulted in the greatest localisation accuracy. [ABSTRACT FROM AUTHOR]

(1) determine if untrained, normal-hearing listeners could learn, with regimented practice trials, to localise a dissonant tonal complex while wearing electronic hearing protectors and achieve equivalent performance to the unoccluded ear, (2) determine if different protector designs affect the localisation learning curve, and (3) determine if a sequential training regimen could be used to determine whether a device is not amenable to training effects. All subjects completed paired training and testing trials, in 12 Learning Units (LU), first with the open ear., then half with device A, a US Army TCAPS (INVISIO® X50), and the other half with device B (a prototype). Both groups then finished with the opposite device. Ten subjects participated, with thresholds below 25 dBHL, bilateral symmetry below 15 dBHL, and naivety with electronic protectors and localisation testing. Subjects eventually approached their open ear capability with device A, but never reached equivalent open ear nor asymptotic performance with device B. Depending upon a protector's sound transduction, frequency response, and other characteristics, different amounts of training are required to adapt. The training protocol has value in determining device acceptability based on the training burden required, especially when mission-related localisation performance is important. [ABSTRACT FROM AUTHOR]

This simulator-based study examined conventional auditory warnings (tonal, nonverbal sounds) and auditory icons (representational, nonverbal sounds), alone and in combination with a dash-mounted visual display, to present information about impending […]

Objective: To design a test battery and conduct a proof-of-concept experiment of a test method that can be used to measure the detection performance afforded by military advanced hearing protection devices (HPDs) and tactical communication and protective systems (TCAPS).Design: The detection test was conducted with each of the four loudspeakers located at front, right, rear and left of the participant. Participants wore 2 in-ear-type TCAPS, 1 earmuff-type TCAPS, a passive Combat Arms Earplug in its “open” or pass-through setting and an EB-15LE™ electronic earplug. Devices with electronic gain systems were tested under two gain settings: “unity” and “max”. Testing without any device (open ear) was conducted as a control.Study sample: Ten participants with audiometric requirements of 25 dBHL or better at 500, 1000, 2000, 4000, 8000 Hz in both ears.Results: Detection task performance varied with different signals and speaker locations. The test identified performance differences among certain TCAPS and protectors, and the open ear. Conclusions: A computer-controlled detection subtest of the Detection-Recognition/Identification-Localisation-Communication (DRILCOM) test battery was designed and implemented. Tested in a proof-of-concept experiment, it showed statistically-significant sensitivity to device differences in detection effects with the small sample of participants (10). This result has important implications for selection and deployment of TCAPS and HPDs on soldiers and workers in dynamic situations. [ABSTRACT FROM PUBLISHER]

Objective: To determine if training with electronically-modulated hearing protection (EMHP) and the open ear results in auditory learning on a horizontal localization task. Design: Baseline localization testing was conducted in three listening conditions (open-ear, in-the-ear (ITE) EMHP, and over-the-ear (OTE) EMHP). Participants then wore either an ITE or OTE EMHP for 12, almost daily, one-hour training sessions. After training was complete, participants again underwent localization testing in all three listening conditions. A computer with a custom software and hardware interface presented localization sounds and collected participant responses. Study sample: Twelve participants were recruited from the student population at Virginia Tech. Audiometric requirements were 35 dBHL at 500, 1000, and 2000 Hz bilaterally, and 55 dBHL at 4000 Hz in at least one ear. Results: Pre-training localization performance with an ITE or OTE EMHP was worse than open-ear performance. After training with any given listening condition, including open-ear, performance in that listening condition improved, in part from a practice effect. However, post-training localization performance showed near equal performance between the open-ear and training EMHP. Auditory learning occurred for the training EMHP, but not for the non-training EMHP; that is, there was no significant training crossover effect between the ITE and the OTE devices. Conclusion: It is evident from this study that auditory learning (improved horizontal localization performance) occurred with the EMHP for which training was performed. However, performance improvements found with the training EMHP were not realized in the non-training EMHP. Furthermore, localization performance in the open-ear condition also benefitted from training on the task. [ABSTRACT FROM AUTHOR]