Communication Headsets Research Articles

Evaluation of Noise Exposure and Hearing Threshold Levels Among Call Centre Operators

The aim of this study was to evaluate the hearing status of call centre operators in relation to their noise exposure. Conventional pure-tone audiometry and extended high-frequency audiometry were performed in 49 workers, aged 22–47 years (mean ± SD: 32.0 ± 6.0 years), working in call centre from 1.0 to 16.5 years (mean ± SD: 4.7 ± 2.9 years). Questionnaire inquiry aimed at collecting personal data, the information on ommunication headset usage habits, self-assessment of hearing ability and identification of risk factors for noise-induced hearing loss were also carried out. Sound pressure levels generated by the communication headset were determined using the artificial ear technique specified in CSA Z107.56-13 (2013) standard. The background noise prevailing in offices was also measured according to PN-N-01307 (1994) and PN-EN ISO 9612 (2011). Personal daily noise exposure levels in call centre operators varied from 66 to 86 dB (10–90th percentile). About half of the study subjects had normal hearing in the standard frequencies (from 250 to 8000 Hz) in both ears, while only 27.1% in the extended high-frequencies (9–16 kHz). Moreover, both high-frequency and speech-frequency hearing losses were observed in less than 10% of audiograms, while the extended high-frequency threshold shift was noted in 37.1% of analysed ears. The hearing threshold levels of call centre operators in the frequency of 0.25–11.2 kHz were higher (worse) than the expected median values for equivalent (due to age and gender) highly screened population specified in ISO 7029 (2017). Furthermore, they were also higher than predicted for 500–4000 Hz according to ISO 1999 (2013) based on the results of noise exposure evaluation.

Hearing Through Bone Conduction Headsets.

Bone conduction (BC) stimulation has mainly been used for clinical hearing assessment and hearing aids where stimulation is applied at the mastoid behind the ear. Recently, BC has become popular for communication headsets where the stimulation position often is close to the anterior part of the ear canal opening. The BC sound transmission for this stimulation position is here investigated in 21 participants by ear canal sound pressure measurements and hearing threshold assessment as well as simulations in the LiUHead. The results indicated that a stimulation position close to the ear canal opening improves the sensitivity for BC sound by around 20 dB but by up to 40 dB at some frequencies. The transcranial transmission ranges typically between -40 and -25 dB. This decreased transcranial transmission facilitates saliency of binaural cues and implies that BC headsets are suitable for virtual and augmented reality applications. The findings suggest that with BC stimulation close to the ear canal opening, the sound pressure in the ear canal dominates the perception of BC sound. With this stimulation, the ear canal pathway was estimated to be around 25 dB greater than other contributors, like skull bone vibrations, for hearing BC sound in a healthy ear. This increased contribution from the ear canal sound pressure to BC hearing means that a position close to the ear canal is not appropriate for clinical use since, in such case, a conductive hearing loss affects BC and air conduction thresholds by a similar amount.

Noise exposure and hearing status among employees using communication headsets.

The objective of this study was to assess the hearing of employees using communication headsets with regard to their exposure to noise. The study group comprised 213 employees, including 21 workers of the furniture industry, 15 court transcribers and 177 call center operators, aged 19-55 years, working with headsets for a period of up to 25 years. All the participants underwent a standard puretone audiometry, extended high-frequency audiometry (EHFA) as well as transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs). Noise exposure from headsets was evaluated using the microphone in a real ear technique according to PN-EN ISO 11904-1:2008. Personal daily noise exposure levels ranged 57-96 dB and exceeded 85 dB only in 1.4% of the call center operators. Forty-two percent of the participants had bilateral normal hearing in the standard frequency range of 250-8000 Hz, and 33% in the extended highfrequency range of 9-16 kHz. It was found that DPOAEs were present bilaterally in 59% of the participants. Reproducibility of TEOAE at >70% and signal-to-noise ratio at >6 was exhibited by 42% and 17% of them, respectively. The 3 subgroups of workers differed in age, gender, noise exposure and type of headsets in use. However, after adjusting for age and gender, significant differences between these subgroups in terms of hearing were mostly visible in EHFA. A significant impact of age, gender, daily noise exposure level and current job tenure on hearing tests results was also noted among the call center operators and the transcribers. The most pronounced were the effects of age and gender, whereas the impact of the daily noise exposure level was less evident. It seems that EHFA is useful for recognizing early signs of noise-induced hearing loss among communication headset users. However, further studies are needed before any firm conclusions concerning the risk of hearing impairment due to the use of such devices can be drawn. Int J Occup Med Environ Health. 2022;35(5):585-614.

HALO CleanSpace PAPR evaluation: Communication, respiratory protection, and usability.

To evaluate a relatively new half-face-piece powered air-purifying respirator (PAPR) device called the HALO (CleanSpace). We assessed its communication performance, its degree of respiratory protection, and its usability and comfort level. This simulation study was conducted at the simulation center of the Royal Melbourne Hospital. In total, 8 voluntary healthcare workers participated in the study: 4 women and 4 men comprising 3 nursing staff and 5 medical staff. We performed the modified rhyme test, outlined by the National Institute for Occupational Safety and Health (NIOSH), for the communication assessment. We conducted quantitative fit test and simulated workplace protection factor studies to assess the degree of respiratory protection for participants at rest, during, and immediately after performing chest compression. We also invited the participants to complete a usability and comfort survey. The HALO PAPR met the NIOSH minimum standard for speech intelligibility, which was significantly improved with the addition of wireless communication headsets. The HALO provided consistent and adequate level of respiratory protection at rest, during and after chest compression regardless of the device power mode. It was rated favorably for its usability and comfort. However, participants criticized doffing difficulty and perceived communication interference. The HALO device can be considered as an alternative to a filtering face-piece respirator. Thorough doffing training and mitigation planning to improve the device communication performance are recommended. Further research is required to examine its clinical outcomes and barriers that may potentially affect patient or healthcare worker safety.

Evaluation of Extended-Wear Hearing Aids as a Solution for Intermittently Noise-Exposed Listeners With Hearing Loss.

Many individuals with noise-related hearing loss continue working in environments where they are periodically exposed to high levels of noise, which increases their risk for further hearing loss. These individuals often must remove their hearing aids in operational environments because of incompatibility with the mandated personal protective equipment, thus reducing situational awareness. Extended-wear hearing aids might provide a solution for these individuals because they can be worn for weeks or months at a time, protect users from high-level noise exposures, and are compatible with communication headsets, earmuffs, and other types of personal protective equipment. The purpose of this study was to evaluate localization ability and speech understanding, feasibility of fitting and use, and acceptability in terms of comfort in a population of noise-exposed, active duty Service members. Participants in the study were active duty Service members who were experienced hearing aid users and were currently using standard hearing aids bilaterally. Participants were fitted with extended-wear hearing aids for up to 14 weeks. Laboratory measures included functional gain, sound localization, and speech recognition (in quiet and in noise). Performance was compared between unaided, standard hearing aids, extended-wear hearing aids, and extended-wear hearing aids combined with a tactical communication device (3M Peltor ComTac). In addition, self-perceived benefit between extended-wear hearing aids and standard hearing aids was compared. The extended-wear hearing aids provided more attenuation of external sound when turned off compared to standard hearing aids. Speech understanding in quiet and in noise was comparable between extended-wear hearing aids and standard hearing aids and was better when a tactical communication device was worn in addition to extended-wear hearing aids. Localization with extended-wear hearing aids was the worst, intermediate with the standard hearing aids, and the best when the ears were unaided. The extended-wear hearing aids and standard hearing aids provided similar self-perceived communication benefits relative to unaided ears. Device failure and issues with extended-wear hearing aids fit and comfort contributed to a high participant withdrawal rate. Overall, the hearing benefits of extended-wear hearing aids for Service members with hearing loss were comparable to those obtained with standard hearing aids, except for sound localization, which was poorer with extended-wear hearing aids. Extended-wear hearing aids provide the additional benefits of protecting the ears from high-level impulsive noise and being compatible with tactical communication and protection systems and other existing personal protective equipment and communication gear. The withdrawal rate in this study, however, suggests that extended-wear hearing aids may not be suitable for active duty Service members in locations where properly trained hearing professionals are not available to replace or re-insert extended-wear hearing aids when needed due to discomfort or device failure.

Evaluation of noise exposure and risk of hearing impairment in employees using communication headsets or headphones

The aim of the study was to assess the noise exposure and risk of noise-induced hearing loss (NIHL) among users of communication headsets (CHs) or headphones. Noise measurements and questionnaire surveys were carried out in 74 workers (aged: 31.8±7.3 years), including military aviation personnel (N = 12), transcribers (N = 18) and call center operators (N = 44). Sound pressure levels (SPLs) emitted by CHs (or headphones) were determined using the microphone in the real ear (MIRE) technique and artificial ear techniques according to PN-EN ISO 11904-1:2008 and CSA Z107.56-13, respectively. The risk of NIHL was evaluated in accordance with PN-ISO 1999:2000. The diffused-field-related A-weighted equivalent-continuous SPLs measured under CHs (or headphones) using the MIRE and artificial ear techniques reached values of 67-86 dB (10-90th percentile) and 68-89 dB (10-90th percentile), respectively. The study subjects used these devices 1.5-8 h (10-90th percentile) per day. Exposure to such noise levels for 40 years of employment causes the risk of hearing impairment (mean hearing threshold level for 2, 3 and 4 kHz > 25 dB) up to 10-12% (MIRE technique) or 19-22% (artificial ear technique). Individual daily noise exposure levels in study group varied 71-85 dB (10-90th percentile). A number of workers complained of problems with understanding speech in noisy environment (28.4%) and hearing whisper (16.2%) and experienced post-work temporary hearing symptoms (16.2-25.7%) as well. The users of CHs and headphones should be included in the hearing conservation program. Further studies are also needed among employees of other industries. Med Pr. 2019;70(1):27-52.

An indirect calculation method for estimating occupational sound exposure from communication headsets.

Measurement of noise exposure from communication headsets is challenging due to the need for specialized equipment, methods, and training. Canadian standard Z107.56-13 [(2013). Measurement of Noise Exposure (Canadian Standards Association, Mississauga, Canada)] introduced a calculation procedure to promote a simpler method that stakeholders in hearing loss prevention could readily apply using widely accessible sound level equipment. The original procedure specified a fixed signal-to-noise ratio (SNR) of 15 dB above the protected background noise when estimating the speech listening level through the headset communication channel. The relationship between background noise level, noise type, headset noise reduction (NR), and speech listening level is revisited in this study. In a noise simulation room, 24 participants were asked to adjust the headset volume while listening to speech and executing a visual reaction task. Results indicate that the growth in speech listening levels with noise is not adequately represented by a fixed SNR, and that one-sided listening increases speech levels by about 5-7 dB in quiet and in noise compared to two-sided listening. Moreover, use of an octave-band procedure with derating to estimate headset NR best captured the speech listening level data. A revised calculation procedure based on linear regression modeling is described with parameters adjusted separately for one-sided and two-sided headsets.

Speech-in-noise research: From classrooms to Canadian Armed Forces operational environments

The importance of speech intelligibility in learning and occupational environments is evidenced by the abundance of research in room acoustics and auditory communication. In addition to environmental factors such as background noise and reverberation, individual factors including the presence of hearing loss, wearing of hearing aids and hearing protection devices (HPDs), and language proficiency must be considered. Previous work in these areas has provided a benchmark for the study of communication in complex, high noise environments. For Canadian Armed Forces (CAF) members, the high noise levels inside aircraft, armoured vehicles and sea vessels demand the use of HPDs and integrated radio communication systems. This presentation will summarize our research on speech understanding in noise and multi-talker environments using different communication headsets, simulated hearing loss and language proficiency. We will focus on our recent studies of communication between native (L1) and non-native (L2) English speakers, which is applicable to the CAF due to the relatively high percentage of L2 membership. L2 speakers obtained lower scores on speech-in-noise tests than L1 speakers for both radioed and face-to-face speech, despite having a high level of language proficiency. Preliminary results of an investigation of cognitive load for L2 listeners will also be presented.

Noise exposure and hearing status among call center operators.

Introduction:The overall objective of the study was to assess noise exposure and audiometric hearing threshold levels (HTLs) in call center operators.Materials and Methods:Standard pure-tone audiometry and extended high-frequency audiometry were performed in 78 participants, aged 19 to 44 years (mean ± standard deviation: 28.1 ± 6.3 years), employed up to 12 years (2.7 ± 2.9 years) at one call center. All participants were also inquired about their communication headset usage habits, hearing-related symptoms, and risk factors for noise-induced hearing loss (NIHL). Noise exposure under headsets was evaluated using the microphone in a real ear technique as specified by ISO 11904-1:2002. The background noise prevailing in offices was also measured according to ISO 9612:2009.Results and Discussion:A personal daily noise exposure level calculated by combining headset and nonheadset work activities ranged from 68 to 79 dBA (74.7 ± 2.5 dBA). Majority (92.3%) of study participants had normal hearing in both ears (mean HTL in the frequency range of 0.25–8 kHz ≤20 dB HL). However, their HTLs in the frequency range of 0.25 to 8 kHz were worse than the expected median values for equivalent highly screened otologically normal population, whereas above 8 kHz were comparable (9–11.2 kHz) or better (12.5 kHz). High-frequency hearing loss (mean HTLs at 3, 4, and 6 kHz >20 dB HL) and speech-frequency hearing loss (mean HTLs at 0.5, 1, 2, and 4 kHz >20 dB HL) were noted in 8.3% and 6.4% of ears, respectively. High-frequency notches were found in 15.4% of analyzed audiograms. Moreover, some of call center operators reported hearing-related symptoms.Conclusions:Further studies are needed before firm conclusions concerning the risk of NIHL in this professional group can be drawn.

Communication in military environments: Influence of noise, hearing protection and language proficiency

Military training and international operations require different nationalities to communicate in a common language, where there are potential challenges with non-native (L2) speech communication. An experiment of speech communication in military noise was conducted for co-located (face-to-face [F2F]) and distributed (using communication headsets) talker-listener pairs. Half of the twenty-four participants were monolingual English speakers (native group, NA) and the remaining half had obtained English fluency after the age of eight years (non-native group, NN). Two tests of speech understanding were used: the Modified Rhyme Test (MRT) and the Speech Perception in Noise test (SPIN). In the F2F condition, the participants wore a communication headset (earmuff) with the power off for occluded listening. Three levels of armoured vehicle noise were used, 55, 60 and 65dBA, for speech-to-noise ratios ranging from −10 to +5dB. In the radio condition, the pairs were separated by a visual barrier and used the communication headset for the tests in 80dBA armoured vehicle noise. The results showed that the NN group had difficulty with the SPIN test in the radio and F2F conditions. This result was attributed to the open-response set of the SPIN. Headset occlusion likely contributed to the lower scores for the NN listeners in the F2F condition. There was a main effect of talker for the MRT in the F2F and radio conditions, and for the SPIN in the radio condition, suggesting that foreign accent reduced the intelligibility for both the NA and NN groups. The results were surprising considering the high L2 proficiency of the NN group. Training methods for improving L2 communication in operational settings should be further investigated.

Evaluation of a calculation method of noise exposure from communication headsets

Specialized standardized methods for the measurement of noise exposure from communication headsets or sound sources close to the ear include the Microphone in Real Ear and manikin techniques, as specified in ISO 11904-1/2. The 2013 version of Canadian standard Z107.56 introduced a simpler calculation method to increase accessibility to communication headset exposure assessments for the widest range of stakeholders in hearing loss prevention. The calculation method only requires general and widely accessible sound measurement equipment and basic computational steps that account for the main determinants of exposure such as the background noise around the user, the sound attenuation of the communication headset, and the expected communication duration and effective listening signal-to-noise ratio. This paper reviews recent research on the effects of the spectral and temporal characteristics of the background noise and the headset configuration on the speech listening level. Results indicate that the listening level is largely insensitive to spectral and temporal variations in the background noise and that A-weighted noise level is a good predictor of listening level once headset attenuation is taken into account. It is also found that one-sided headsets increase exposure by 6-7 dB compared to two-sided headsets due to binaural summation.

The effect of sensorineural hearing loss and tinnitus on speech recognition over air and bone conduction military communications headsets

Military personnel are at risk for hearing loss due to noise exposure during deployment (USACHPPM, 2008). Despite mandated use of hearing protection, hearing loss and tinnitus are prevalent due to reluctance to use hearing protection. Bone conduction headsets can offer good speech intelligibility for normal hearing (NH) listeners while allowing the ears to remain open in quiet environments and the use of hearing protection when needed. Those who suffer from tinnitus, the experience of perceiving a sound not produced by an external source, often show degraded speech recognition; however, it is unclear whether this is a result of decreased hearing sensitivity or increased distractibility (Moon et al., 2015). It has been suggested that the vibratory stimulation of a bone conduction headset might ameliorate the effects of tinnitus on speech perception; however, there is currently no research to support or refute this claim (Hoare et al., 2014). Speech recognition of words presented over air conduction and bone conduction headsets was measured for three groups of listeners: NH, sensorineural hearing impaired, and/or tinnitus sufferers. Three levels of speech-to-noise (SNR = 0, −6, −12 dB) were created by embedding speech items in pink noise. Better speech recognition performance was observed with the bone conduction headset regardless of hearing profile, and speech intelligibility was a function of SNR. Discussion will include study limitations and the implications of these findings for those serving in the military.

Speech recognition performance of listeners with normal hearing, sensorineural hearing loss, and sensorineural hearing loss and bothersome tinnitus when using air and bone conduction communication headsets

Military personnel are at risk for hearing loss due to noise exposure during deployment (Norin et al., 2011). Despite mandated use of hearing protection, hearing loss and tinnitus are prevalent due to reluctance to use hearing protection. Bone conduction (BC) headsets can offer good speech intelligibility for normal hearing (NH) listeners while allowing the ears to remain open in quiet environments and the use of hearing protection when needed. Tinnitus sufferers often show degraded speech recognition; however, it is unclear whether this is a result of decreased hearing sensitivity or increased distractibility. It has been suggested that vibratory stimulation of BC might ameliorate tinnitus; however, there is currently no research to support or refute this claim (Hoare, et al., 2014). Speech recognition of words presented over AC and BC headsets was measured for three groups of listeners: NH, sensorineural hearing impaired, and/or tinnitus sufferers. Three levels of speech-to-noise (SNR = 0,−6,−12) were c...

Comparison of different types of hearing protection devices for use during weapons firing

Introduction: Hearing protection devices (HPDs) are not rated for impulse noise, which makes it difficult to select an appropriate device for use during weapons firing. Measurements of different types of HPDs (level independent, level dependent, earplugs, and earmuffs) were performed following American National Standards Institute/Acoustical Society of America S12.42 procedures. Methods: A rifle producing a peak level of 154 decibels of sound pressure level was used as the noise source for the measurements. The devices tested were E-A-R Classic earplugs, Combat Arms double-end earplugs, ETY·Plugs earplugs (standard fit), Peltor H10A earmuffs, and Peltor PowerCom Plus earmuffs. The earmuffs were also tested in combination with the E-A-R Classic earplugs and with ballistic glasses. Results: The earplug and earmuff combinations provided the most protection, followed by the level-independent earplugs, earmuffs, and level-dependent earplugs. Wearing of ballistic glasses reduced the effectiveness of the earmuffs. Discussion: Although the results provide information about the level of protection that is possible for several types of HPDs, the best choice of HPD depends on the operational setting. The combination of level-independent earmuffs and earplugs was the most effective, but it is not a practical solution when communication is required. Earplugs should be worn in cases in which earmuffs interfere with sighting the weapon or are incompatible with other gear such as a helmet or glasses. Future work should include different types of communication headsets and different combinations of HPDs.

Calculating total daily noise exposure using aircrew flight equipment noise attenuation and fight segment noise data

The workplace of military aircrew is louder and more varied than most industrial environments. In the recent revision of MIL-STD-1474E, Noise Limits, octave band level design limits for helicopters have been replaced by a broader requirement based on noise exposure at the ear. This change brings 1474E into alignment with DoD hearing conservation policies which require that total daily noise exposure does not exceed an Leq of 85 dBA during an 8 hour period. Although these polices also require use of hearing protection whenever levels exceed 85 dBA, there is currently little written guidance for how to use hearing protector attenuation data to estimate exposure at the ear over the course of a typical mission profile. This paper will explain how attenuation data for flight helmets and communication headsets has been used by the Naval Air Systems Command to estimate noise exposure for crew and passengers in various types of aircraft.

스마트 웨어러블 지뢰탐지 장치 연구

current mine detector can`t division the section if it is conducted and it needs too much labor force and time. in addition to, if the user don`t move the head of sensor in regular speed or move it too fast, it is hard to detect a mine exactly. according to this, to improve the problem using one direction ultrasonic wave sensing signal, that is made up of human body antenna part, main micro processor unit part, smart glasses part, body equipped LCD monitor part, wireless data transmit part, belt type power supply part, black box type camera, Security Communication headset. the user can equip this at head, body, arm, waist and leg in removable type. so it is able to detect the powder in a 360-degree on(under) the ground whether it is metal or nonmetal and it can express the 2D or 3D film about distance, form and material of the mine. so the battle combats can avoid the mine and move fast. also, through the portable battery and twin self power supply system of the power supply part, combat troops can fight without extra recharge and we can monitoring the battle situation of distant place at the command center server on real-time. and then, it makes able to sharing the information of battle among battle combats one on one. as a result, the purpose of this study is researching a smart wearable mine detector which can establish a smart battle system as if the commander is in the site of the battle.

Comparison of impulse peak insertion loss measured with gunshot and shock tube noise sources

The National Institute for Occupational Safety and Health in cooperation with scientists from 3M and the U.S. Army Aeromedical Research Laboratory conducted a series of Impulse peak insertion loss (IPIL) tests of the acoustic test fixtures from the Institute de Saint Louis (ISL) with a 0.223 caliber rifle and two different acoustic shock tubes. The Etymotic Research ETYPlugs™ earplug, 3M™ TacticalPro™ communication headset and the dual protector combination were tested with all three impulse noise sources. The spectra, IPIL, and the reduction of different damage risk criteria will be presented. The spectra from the noise sources vary considerably with the rifle having peak energy at about 1000 Hz. The shock tubes had peak levels around 125 and 250 Hz. The IPIL values for the rifle were greater than those measured with the two shock tubes. The shock tubes had comparable IPIL results except at 150 dB for the dual protector condition. The treatment of the double protection condition is complicated because the earmuff reduces the shock wave and reduces the effective level experienced by the earplug. For the double protection conditions, bone conduction presents a potential limiting factor for the effective attenuation that can be achieved by hearing protection.

Strategies to combat auditory overload during vehicular command and control.

Strategies to combat auditory overload were studied. Normal-hearing males were tested in a sound isolated room in a mock-up of a military land vehicle. Two tasks were presented concurrently, in quiet and vehicle noise. For Task 1 dichotic phrases were delivered over a communications headset. Participants encoded only those beginning with a preassigned call sign (Baron or Charlie). For Task 2, they agreed or disagreed with simple equations presented either over loudspeakers, as text on the laptop monitor, in both the audio and the visual modalities, or not at all. Accuracy was significantly better by 20% on Task 2 when the equations were presented visually or audiovisually. Scores were at least 78% correct for dichotic phrases presented over the headset, with a right ear advantage of 7%, given the 5 dB speech-to-noise ratio. The left ear disadvantage was particularly apparent in noise, where the interaural difference was 12%. Relatively lower scores in the left ear, in noise, were observed for phrases beginning with Charlie. These findings underscore the benefit of delivering higher priority communications to the dominant ear, the importance of selecting speech sounds that are resilient to noise masking, and the advantage of using text in cases of degraded audio.

A human factors subsystems approach to trauma care.

A physician-centered approach to systems design is fundamental to ameliorating the causes of many errors, inefficiencies, and reliability problems. To use human factors engineering to redesign the trauma process based on previously identified impediments to care related to coordination problems, communication failures, and equipment issues. This study used an interrupted time series design to collect historically controlled data via prospective direct observation by trained observers. We studied patients from a level I trauma center from August 1 through October 31, 2011, and August 1 through October 31, 2012. A range of potential solutions based on previous observations, trauma team engagement, and iterative cycles identified the most promising subsystem interventions (headsets, equipment storage, medication packs, whiteboard, prebriefing, and teamwork training). Five of the 6 subsystem interventions were successfully deployed. Communication headsets were found to be unsuitable in simulation. The primary outcome measure was flow disruptions, with treatment time and length of stay as secondary outcome measures. A total of 86 patients were observed before the intervention and 120 after the intervention. Flow disruptions increased if the patient had undergone computed tomography (CT) (F1200 = 20.0, P < .001) and had been to the operating room (F1200 = 63.1, P < .001), with an interaction among the intervention, trauma level, and CT (F1200 = 6.50, P = .01). For total treatment time, there was an effect of the intervention (F1200 = 21.7, P < .001), whether the patient had undergone CT (F1200 = 43.0, P < .001), and whether the patient had been to the operating room (F1200 = 85.8, P < .001), with an interaction among the intervention, trauma level, and CT (F1200 = 15.1, P < .001), reflecting a 20- to 30-minute reduction in time in the emergency department. Length of stay was reduced significantly for patients with major mortality risk (P = .01) from a median of 8 to 5 days. Deployment of complex subsystem interventions based on detailed human factors engineering and a systems analysis of the provision of trauma care resulted in reduced flow disruptions, treatment time, and length of stay.

Understanding speech when wearing communication headsets and hearing protectors with subband processing.

An adaptive, delayless, subband feed-forward control structure is employed to improve the speech signal-to-noise ratio (SNR) in the communication channel of a circumaural headset/hearing protector (HPD) from 90 Hz to 11.3 kHz, and to provide active noise control (ANC) from 50 to 800 Hz to complement the passive attenuation of the HPD. The task involves optimizing the speech SNR for each communication channel subband, subject to limiting the maximum sound level at the ear, maintaining a speech SNR preferred by users, and reducing large inter-band gain differences to improve speech quality. The performance of a proof-of-concept device has been evaluated in a pseudo-diffuse sound field when worn by human subjects under conditions of environmental noise and speech that do not pose a risk to hearing, and by simulation for other conditions. For the environmental noises employed in this study, subband speech SNR control combined with subband ANC produced greater improvement in word scores than subband ANC alone, and improved the consistency of word scores across subjects. The simulation employed a subject-specific linear model, and predicted that word scores are maintained in excess of 90% for sound levels outside the HPD of up to ∼115 dBA.