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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]

Objective: To determine the effects of current hearing protection/enhancement devices (HPEDs) and tactical communications and protection systems (TCAPS) on auditory detection and identification of three critical military signals associated with potential 'threats.' Design: Utilizing a 6 × 3 within-subject experimental design, 24 normal-hearing Virginia Tech Reserve Officer Training Corps (ROTC) cadets and active duty soldiers participated. Study sample: Five HPEDS and TCAP devices plus the open ear were tested. On each trial, either wearing a device or with open ears, subjects walked along a 3000-foot line of discrete distance markers toward the auditory threat, which was not visible but still within line-of-sight over flat terrain, stopping to listen when instructed. On approach to the threat, the linear distance at first detection was measured, followed by a continued approach until positive identification occurred. Then the subject reversed direction, retreating away from the threat until detection was lost. Results: ANOVA and post hoc tests were applied to determine statistically-significant differences among HPEDs, TCAPS, and the open ear on the objective detection and identification distance measures. Conclusions: The results have serious implications for selection of HPDs, HPEDs, and TCAPS for applications where preservation of auditory situational awareness via the fundamental detection and identification tasks are essential. [ABSTRACT FROM AUTHOR]

Objective: This study was designed to determine the effects of hearing loss, aviation headset type, flight workload complexity, and communication signal quality on pilots' performance in an army rotary-wing flight simulator.Background: To maintain flight status, army aviators who do not meet current audiometric standards require a hearing loss waiver, which is based on speech intelligibility in quiet conditions. Because hearing loss characteristics of hearing-impaired aviators can vary greatly, and because performance is likely also influenced by degree of flight workload and communication demand, it was expected that performance among hearing-impaired aviators would also vary.Method: Participants were 20 army helicopter pilots. Pilots flew three flights in a full motion-based helicopter simulator,with a different headset configuration and varying flight workload levels and communication signal quality characterizing each flight. Objective flight performance parameters of heading, altitude, and airspeed deviation and air traffic control command read-backs were measured.Results: Statistically significant results suggest that high levels of flight workload, especially in combination with poor communications signal quality, lead to deficits in flight performance and speech intelligibility.Conclusion: These results support a conclusion that factors other than hearing thresholds and speech intelligibility in quiet should be considered when evaluating helicopter pilots' flight safety. The results also support a recommendation that hearing-impaired pilots use assistive communication technology and not fly with strictly passive headsets.Application: The combined effects of flight environment with individual hearing levels should be considered when making recommendations concerning continued aviation flight status and those concerning communications headsets used in high-noise cockpits. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess normal hearing listeners' performance in detecting a stationary backup alarm signal and to quantify the linear distance at detection point. Method: Detection distances for 12 participants with normal hearing were measured while they were fitted with 7 hearing protectors and while they were unoccluded (open ear). A standard (narrowband) backup alarm signal and a broadband (pulsed white noise) backup alarm signal from Brigade[1] were used. The method of limits, with distance as the physical measurement variable and threshold detection as the task, was employed to find at which distance the participant could first detect the backup alarms. Results: A within-subject Analysis of Variance (ANOVA) revealed a significant main effect of the listening conditions on the detection distance in feet. Post hoc analyses indicated that the Bilsom L3HV conventional passive earmuff (at 1132.2 ft detection distance) was significantly poorer compared to all other HPDs and the open ear in detection distance achieved, and that there were no statistically-significant differences between the unoccluded ear (1652.3 ft), EB-15-Lo BlastPLGTM (1546.2 ft), EB-15-Hi BlastPLGTM (1543.4 ft), E-A-R/3M Combat ArmsTM earplug-nonlinear, level-dependent state (1507.8 ft), E-A-R/3M HiFiTM earplug (1497.7 ft), and Bilsom ImpactTM dichotic electronic earmuff (1567.2 ft). In addition, the E-A-R/3M Combat ArmsTM earplug-passive steady state resulted in significantly longer detection distances than only the open ear condition, at 1474.1 ft versus 1652.3 ft for the open ear. ANOVA also revealed a significant main effect of the backup alarm type on detection distance. The means were 1600.9 ft for the standard (narrowband) backup alarm signal, and a significantly closer 1379.4 ft was required for the Brigade broadband backup alarm signal. Discussion: For on-ground workers, it is crucial to detect backup alarm signals as far away as possible rather than at close distances since this will provide them more time to react to approaching vehicles. The results of this study suggest that as the attenuation of the hearing protectors increases, precautions should be considered by safety professionals. This is because, as it was the case with the Bilsom passive earmuff and E-A-R/3M Combat ArmsTM earplug-passive steady state, high attenuation minimizes the detection distance and as a result on-foot workers will have less time to react to any approaching vehicle. The main effects of the type of backup alarm signal demonstrated a statistically-significant advantage of the standard backup alarm over the broadband backup alarm on detection distance in feet. The magnitude of the improvement produced by the standard backup alarm was 221.5 feet, a very large margin. For example, with a vehicle backing at 10 mph, the 221.5 ft decrease in detection distance with the Brigade alarm equates to the vehicle arriving 15 seconds sooner at the worker from the point at which its alarm was first heard. [ABSTRACT FROM AUTHOR]

Augmentations or enhancements to conventional HPDs, that is, those which attenuate noise strictly through static, passive means, are generally delineated into passive (non-electronic) and active (powered electronic) designs. While powered electronic augmentations are reviewed in Casali (a parallel paper elsewhere in this issue), passive augmentations are represented by mechanical networks to achieve flat-by-frequency attenuation; level-dependent leakage pathways that house acoustically-variable occluders to yield minimal attenuation during quiet periods but sharply increasing attenuation upon intense noise bursts (such as gunfire); quarter-wave resonance ducts to bolster attenuation of specific frequencies; selectable cartridges or valves that enable passive attenuation to be adjusted for specific exposure needs; and dynamically adjustable-fit devices that provide adjustment features to enable personalized fit to the user as well as some degree of attenuation control. Intended benefits of passive augmented HPDs (akin to those of active devices as well) include (1) more natural hearing for the user, (2) improved speech communications and signal detection, (3) reduced noise-induced annoyance, (4) improved military tactics, stealth maintenance and gunfire protection, and (5) provision of protection that is tailored for the user's needs, noise exposure, and/or job requirements. This paper provides a technical overview of passive augmented HPDs that were available or have been prototyped circa early-2010. In cases where no empirical research results on the passive augmentations and their performance were available in the research literature, this review relied on patents, corporate literature, and/or the author's experience. For certain augmentations, a limited amount of empirical, operational performance research was available and it is covered herein. Finally, in view that at the juncture of this article the United States (U.S.) Environmental Protection Agency (EPA) was in the process of promulgating a comprehensive new federal law to govern the testing and labeling of hearing protectors of various types, those elements of the proposed law that pertain only to specific passive augmentation technologies are mentioned herein, along with references to relevant standards on hearing protector attenuation testing. [ABSTRACT FROM AUTHOR]

Augmented or enhanced hearing protection devices (HPDs), as contrasted with conventional HPDs, which attenuate noise strictly through static, passive means, have proliferated in the past decade. These advancements in HPDs are generally delineated into passive (non-powered) and active (powered electronic) designs. While passive augmentations are reviewed in a parallel paper elsewhere in this issue, active augmentations include various analog and digital circuits for achieving electronic phase cancellation of noise; electronic modulated sound transmission circuits, which amplify a passband of ambient sound and transmit it through the HPD (ceasing to amplify at a pre-determined noise level); and tactical communications and protection systems (TCAPS), which may include any of the aforementioned electronic elements plus microphone/receiver communications elements. The intended benefits of electronic augmented HPDs, some of which are realized in practice and others not, include more natural hearing for the user, improved speech communications and signal detection, reduced noise-induced annoyance, improved military tactics, stealth and gunfire protection, and provision of protection that is somewhat tailored for the user's needs, noise exposure, and/or job requirements. This paper provides a technical overview of active augmented HPDs that were available or have been prototyped circa early-2010. In some cases, no empirical research on the augmentations and their performance was available in the research literature; in these cases, this review relied on patents, corporate literature, and/or the author's experience. For other technologies, a limited amount of empirical, operational performance research was available and it is covered herein. Finally, in view that at the juncture of this article the United States (U.S.) Environmental Protection Agency (EPA) was in the process of promulgating a comprehensive new federal law to govern the testing and labeling of hearing protectors of various types, those elements of the proposed law pertaining to specific augmentation technologies are mentioned herein, along with that proposed law's cited ANSI standards, as well as ISO standards that address hearing protector attenuation testing. [ABSTRACT FROM AUTHOR]

The Microphone in Real Ear or MIRE protocol, standardized as ANSI S12.42-1995, does not specify a standardized location for measurement microphone placement in the human ear. Prior research is mixed as to the potential benefits and/or shortcomings of placing the measurement microphone outside versus inside the ear canal. This study captured and compared spectral attenuation data at three different microphone locations: in the concha of the outer ear, in the ear canal-shallow, and in the ear canal-deep (with a probe tube microphone positioned near the tympanic membrane), using human test participants across five active noise reduction (ANR) headphones of differing design. ANR headphones were used because this paper is an excerpt of a larger research effort designed to assess attenuation measurement methods and instrumentation. Research goals were to determine whether spectral sound pressure levels (SPL) differed significantly at the three microphone locations tested and whether any changes in frequency significantly affected SPL measured at each location; the results showed small, but statistically significant differences between microphone locations, but with frequency-specificity. The results provide assistance to practitioners in determining where to place measurement microphones to best suit their particular needs when using MIRE for hearing protector attenuation testing. [ABSTRACT FROM AUTHOR]

Operational hearing protection and maintenance of audibility of signals and speech are considered force multipliers in military operations, increasing Soldier survivability and lethality. The in-field research described in this paper was conducted to examine operational performance effects of three different hearing enhancement protection systems (HEPS) that are intended to provide both protection and audibility. The experiment utilized operationally-defined measures in full-scale, simulated combat scenarios with Army ROTC Cadet Soldiers as subjects. The Soldiers' operational performance was evaluated in two missions: reconnaissance and raid (attack on enemy camp). Both missions had substantial hearing requirements, including communications, signal detection/recognition, and distance judgments. Operational performance was measured by objective metrics of Squad performance, including the distances required to detect an enemy insurgent camp under each HEPS, and by subjective metrics, such as the Army's dimensions of combat-related mission success as evaluated by Army Officers who served as training leaders/observers. Other subjective ratings were obtained after each training exercise from both the Officers and the Soldiers, including detailed impressions about each HEPS after extended use. Two of the three HEPS were electronic sound transmission devices (comprising an ambient sound pass-through filtering and amplification circuit): a Peltor Comtac II circumaural headset (NRR=21; 16 dB maximum gain); and a Communications Enhancement Protection System (CEPS) (NRR=29; 36 dB maximum gain). One passive, level-dependent HEPS was used, the yellow end of the Combat Arms Earplug, which provides amplitude-sensitive attenuation that sharply increases when the ambient sound is above about 110 dB (e.g., due to a gunshot), but which provides an NRR of 0 and very little attenuation below 1000 Hz in lower ambient noise levels. In the military mission entailing location of and attack on an enemy camp, the CEPS device resulted in the longest (earliest) average auditory detection distance of the camp (400 feet), followed by the Peltor (233 feet) and then the Combat Arms Earplug (150 feet), in comparison to detection by the unprotected, normal ear at about 220 feet. Commanding officers' ratings of mission performance and overall success slightly favored the electronic HEPS, but these ratings were dependent upon the particular mission undertaken. Ergonomics and usability issues abounded with the electronic HEPS, and the Soldiers' subjective ratings showed variability across all three devices, with device preference depending upon the particular dimension being rated (e.g., comfort vs. hearing ability). Clearly, the results of this in-field experiment demonstrate that more development is needed to achieve the levels of hearing performance and user acceptance from the HEPS that is desirable and needed for combat conditions. In this vein, it is important to note that HEPS designs are continually evolving, and certain upgrades to the three devices evaluated in the late 2006 timeframe of this study have occurred and further evaluations are thus warranted. [ABSTRACT FROM AUTHOR]

The mandate of ASA Working Group S12/WG11 has been to develop ''laboratory and/or field procedure(s) that yield useful estimates of field performance'' of hearing protection devices (HPDs). A real-ear attenuation at threshold procedure was selected, devised, tested for one earmuff and three earplugs via an interlaboratory study involving five laboratories and 147 subjects, and incorporated into a new standard that was approved in 1997 [Royster et al., ''Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise,'' J. Acoust. Soc. Am. 99, 1506-1526; ANSI, S12.6-1997, ''American National Standard method for measuring real-ear attenuation of hearing protectors'' (American National Standards Institute, New York, 1997)]. The subject-fit methodology of ANSI S12.6-1997 relies upon listeners who are audiometrically proficient, but inexperienced in the use of HPDs. Whenever a new method is adopted, it is important to know the effects of variability on the power of the measurements. In evaluation of protector noise reduction determined by experimenter-fit, informed-user-fit, and subject-fit methods, interlaboratory reproducibility was found to be best for the subject-fit method. Formulas were derived for determining the minimum detectable difference between attenuation measurements and for determining the number of subjects necessary to achieve a selected level of precision. For a precision of 6 dB, the study found that the minimum number of subjects was 4 for the Bilsom UF-1 earmuff, 10 for the E.A.R Classic earplug, 31 for the Willson EP100 earplug, and 22 for the PlasMed V-51R earplug. [ABSTRACT FROM AUTHOR]

In order to provide a fabric sound evaluation system for designing auditory-sensible fabrics, sound parameters are obtained, including the level pressure of total sound (LPT), sound color factors (ΔL and Δf), three coefficients (ARC, ARF, ARE) of autoregressive models based on the fast fourier transform spectrum, loudness(Z) and sharpness(Z) from Zwicker's psychoacoustic models, and mechanical properties from KES values for wool suiting fabrics. As psychophysical characteristics, subjective sensations of softness, loud ness, sharpness, clearness, roughness, highness, and pleasantness of the fabric sounds are evaluated by the free modulus magnitude estimation. Tropical wool has the lowest loudness(Z) and the highest ΔL value among the fabrics. Melton, a thicker and heavier woolen, shows a trend similar to saxony and flannel for sound parameters. Wool suiting fabrics have higher scores for loudness and highness rather than clearness and pleasant ness, except for tropical wool, which has the highest scores for pleasantness among the fabrics. Using the modified stepwise regression of Kawabata, all sensations are predicted by both sound parameters and mechanical properties. The sound sensation of wool suiting fabrics is related mainly to tensile, surface, and shear properties in mechanical measure ments and with autoregressive coefficients as sound parameters. [ABSTRACT FROM PUBLISHER]

A flight simulator-based study was conducted to examine fourteen distinct mental workload estimation measures, including opinion, secondary task, physiological, and primary task measures. Both the relative sensitivity of the measures to changes in mental workload and the differential intrusion of the changes on primary task performance were assessed. The flight task was varied in difficulty by manipulation of the presentation rate and complexity of a hazard-perception task that required each of 48 licensed pilots to rely heavily on their perceptual abilities. Three rating scales (Modified Cooper-Harper, Multi-descriptor, and Workload-Compensation-Interference/Technical Effectiveness), two secondary task measures (time estimation and tapping regularity), one physiological measure (respiration frequency), and one primary task measure (danger-condition response time) were reliable indicants of workload changes. Recommendations for applying the workload measures are presented. [ABSTRACT FROM PUBLISHER]

The mandate of ASA Working Group S12/WG11 has been to develop 'laboratory and/or field procedure(s) that yield useful estimates of field performance' of hearing protection devices (HPDs). A real-ear attenuation at threshold procedure was selected, devised, tested via an interlaboratory study, and incorporated into a draft standard that was approved in 1997 [J. D. Royster et al., 'Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise,' J. Acoust. Soc. Am. 99, 1506-1526 (1996); ANSI S12.6-1997, 'American National Standard Methods for Measuring Real-Ear Attenuation of Hearing Protectors' (American National Standards Institute, New York, 1997)]. The real-world estimation procedure utilizes a subject-fit methodology with listeners who are audiometrically proficient, but inexperienced in the use of HPDs. A key factor in the decision to utilize the subject-fit method was an evaluation of the representativeness of the laboratory data vis-à-vis attenuation values achieved by workers in practice. Twenty-two field studies were reviewed to develop a data base for comparison purposes. Results indicated that laboratory subject-fit attenuation values were typically equivalent to or greater than the field attenuation values, and yielded a better estimate of those values than did experimenter-fit or experimenter-supervised fit types of results. Recent data which are discussed in the paper, but which were not available at the time of the original analyses, confirm the findings. © 1998 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

This paper describes research conducted by Working Group 11 of Accredited Standards Committee S12, Noise, to develop procedures to estimate the field performance of hearing protection devices (HPDs). Current standardized test methods overestimate the attenuation achieved by workers in everyday use on the job. The goal was to approximate the amount of attenuation that can be achieved by noise-exposed populations in well-managed real-world hearing conservation programs, while maintaining acceptable interlaboratory measurement variability. S12/WG11 designed two new laboratory-based protocols for measuring real-ear attenuation at threshold, with explicit procedures for subject selection, training, supervision, and HPD fitting. After pilot-testing, S12/WG11 conducted a full-scale study of three types of earplugs and one earmuff tested by four independent laboratories using both protocols. The protocol designated as ''subject-fit'' assessed the attenuation achieved by subjects who were experienced in threshold audiometry, but naive with respect to the use of hearing protection, when they fit HPDs by following manufacturers' instructions without any experimenter assistance. The attenuation results from the subject-fit method corresponded more closely to real-world data than results from the other protocol tested, which allowed the experimenter to coach subjects in HPD use. Comparisons of interlaboratory measurement variability for the subject-fit procedure to previous interlaboratory studies using other protocols indicated that the measurements with the new procedure are at least as reproducible as those obtained with existing standardized methods. Therefore, the subject-fit protocol was selected for consideration for use in future revisions of HPD attenuation test standards. © 1996 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented which discusses topics within the issue including various aspects of small caliber firearm noise exposures, firearm noise that is not typically experienced by persons using firearms at a target range or when hunting, and noise exposure risks.

Objective: To investigate the effect of controlled low-speed wind-noise on the auditory situation awareness performance afforded by military hearing protection/enhancement devices (HPED) and tactical communication and protective systems (TCAPS).Design: Recognition/identification and pass-through communications tasks were separately conducted under three wind conditions (0, 5, and 10 mph). Subjects wore two in-ear-type TCAPS, one earmuff-type TCAPS, a 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 subjects were recruited from the student population at Virginia Tech. Audiometric requirements were 25 dBHL or better at 500, 1000, 2000, 4000, and 8000 Hz in both ears.Results: Performance on the interaction of communication task-by-device was significantly different only in 0 mph wind speed. The between-device performance differences varied with azimuthal speaker locations.Conclusions: It is evident from this study that stable (non-gusting) wind speeds up to 10 mph did not significantly degrade recognition/identification task performance and pass-through communication performance of the group of HPEDs and TCAPS tested. However, the various devices performed differently as the test sound signal speaker location was varied and it appears that physical as well as electronic features may have contributed to this directional result. [ABSTRACT FROM PUBLISHER]

A disparity exists between the advertised and realized attenuation of noise by hearing protective devices. The disparity has been accredited to many factors, including overfitting by experimenters and misuse by workers. This study compared attenuation data for three earplugs and one earmuff obtained from an interlaboratory (IL) study using a subject-fit method with data on the same protectors reported in the literature from work-site (WS) studies where workers fitted the hearing protection and with manufacturer-reported (MR) data on NRR labels. The IL method required subjects who where audiometrically competent, but inexperienced with hearing protectors, to fit hearing protectors relying solely upon guidance from the manufacturers' written instructions. Results indicated that there were no differences in attenuations between laboratories. Confidence interval testing was performed comparing the IL mean attenuations and variances to WS means and standard deviations and to MR means and standard deviations. Results indicated that the IL data were more consistent with the WS data than with the MR data. In all cases the IL data were significantly less than the MR data. Depending upon protector type, the IL data were equivalent to or greater than the WS data. [ABSTRACT FROM AUTHOR]

Objective: A controlled field experiment was conducted to evaluate localization of suprathreshold gunshot reports (from blank cartridges) with four hearing protection-enhancement devices (HPEDs) in comparison to the open ear with ambient outdoor noise and in 82 dBA diesel military heavy truck noise. Design: Five measures of localization accuracy and response time for eight shooter positions in azimuth were measured. Study sample: Nine normal-hearing and four impaired-hearing participants were tested. Results: Statistical analysis showed worse accuracy and response time performance with the electronic earmuffs (Peltor Com-Tac II™ in full gain position) than with the other tested HPEDs (Etymotic EB 1 and EB 15 High-Fidelity Electronic BlastPLG™ electronic earplugs, both set to Lo gain positions; and 3M Single-Ended Combat Arms™ passive earplug in level-dependent, 'open' position). Performance with all HPEDs was worse than that with the open ear, except on right-left confusions, in which the earmuff stood alone as worst, and in response time, for which the EB 1 was equivalent to the open ear. There was no significant main effect of noise on performance. Hearing impairment increased right-left confusions. Subjective ratings related to localization generally corroborated objective localization performance. Conclusions: None of the tested HPEDs preserved 'normal' localization performance. [ABSTRACT FROM AUTHOR]

ANSI working group S12/WG11 has been tasked with developing laboratory and/or field procedures that yield useful estimates of the real-world attenuation of hearing protection devices. The first goal selected was the development of a laboratory-based real-car attenuation at threshold (REAT) protocol that would estimate the protection that can be, or is being, obtained in the top 10%-20% of today's hearing conservation programs. A protocol was developed based upon ANSI S 12.6-1984, but with modified subject selection, fitting, and training procedures that were described explicitly and in substantially greater detail than in the standard. Pilot testing of two earplugs in four laboratories with ten naive subjects per facility showed subject-fit attenuation results comparable to available real-world studies. Although subjects achieved significantly greater attenuation after the experimenter demonstrated how to insert the devices (informed user fit), the interlaboratory reproducibility of the group data was not significantly improved. The indications are that a subject-fit protocol, in which experimenter involvement is minimized, yields the best estimates of real-world attenuation, and still provides acceptable reproducibility. The pilot results suggested refinements in the design of a full-scale interlaboratory comparison which should begin in the later part of 1990. [ABSTRACT FROM AUTHOR]