Active noise reduction was first proposed as a solution for environmental noise over fifty years ago. The use of active noise reduction (ANR) systems, however, was not demonstrated until much later. Recent advances in technology have made the use of active noise reduction systems in personal hearing protection devices (HPDs) practical. Through the use of advanced electronics technology, ANR equipped devices offer the potential to provide increased low frequency attenuation for hearing conservation applications. In order to use ANR equipped devices in an Occupational Safety and Health Administration (OSHA) sanctioned hearing conservation program, a testing standard for ANR equipped HPDs needs to be developed. Existing HPD testing standards offer the most promise for developing an acceptable standard for testing ANR-equipped HPDs. The microphone in real ear (MIRE) testing method is one method that offers a practical method for determining the performance of ANR devices for use in hearing conservation programs. A modified version of this method was successfully used in this study to determine the performance profile of an open-back ANR equipped headset. The results of this and other studies that have used a modified MIRE testing method can be used to support the acceptance of this method as the basis of an approved standard for testing ANR-equipped hearing protection devices. / Master of Science

Noise-induced hearing loss and tinnitus are the two most prevalent service-connected disabilities for veterans receiving compensation (Department of Veterans Affairs, 2010). While it is possible to protect against noise-induced hearing damage with hearing protection devices (HPDs) and hearing protection enhancement devices (HPEDs), military personnel resist using HPDs/HPEDs that compromise their situational awareness, including ability to localize enemy gunfire. Manufacturers of a new generation of "pass-through" level-dependent HPEDs claim these devices preserve normal or near-normal hearing. A research study was conducted to evaluate localization of suprathreshold gunshot's report (from blank ammunition) with one passive (3M's Single-Ended Combat Arms earplug) and three electronic level-dependent HPEDs (Peltor's Com-Tac II electronic earmuffs and Etymotic's EB 1 and EB 15 High-Fidelity Electronic BlastPLG earplugs), in comparison to the open ear in an in-field test environment with ambient outdoor noise and in 82 dBA diesel truck noise with nine normal and four impaired hearing participants. Statistical analysis showed worse localization accuracy and response time with the Com-Tac II earmuffs than with the other tested HPEDs. Performance with all HPEDs was worse than that with the open ear, except on right-left confusions, in which the Com-Tac II stood alone as worst, and in response time, for which the EB 1 earplug was equivalent to the open ear. There was no significant main effect of noise level. There was generally no significant effect of hearing ability. However, participants with impaired hearing had more right-left confusions than those with normal hearing. Subjective ratings related to localization generally corroborated objective localization performance. Three follow-up experiments were performed: (1) an assessment of the effect of microphone position on localization with the EB 15, which showed a limited advantage when the microphone was positioned near the opening of the ear canal compared to when it was facing outwards; (2) an assessment of Etymotic's QuickSIN test as a predictor localization performance, which showed little correlation with localization performance; and (3) an assessment of the acoustic properties of the experiment site, which was inconclusive with regards to the direction of dominant sound energy from gunshots from each of the shooter positions. / Ph. D.

Noise exposure is a common hazard to workforce in general although at varying degrees depending on the occupation, as many workers are exposed for long periods of time to potentially hazardous noise. Every year, twenty-two million workers are exposed to potentially damaging noise at work. In 2015 U.S. businesses paid over $1.5 million in penalties for not protecting workers from noise. (OSHA, 2016). There may be a direct or indirect consequence of the possibilities of overexposure to noise notwithstanding the compulsory hearing protection requests for the occupations with potential hazards, and these exposures usually arise from the various types of heavy repair equipment and tools related to the job functions. In the United States ten million people have noise related hearing loss (CDC, 2016) and damage done to the ear is not noticed until earing diminishes significantly. One of the noisiest occupations there are include the flight ground crews and flight maintenance personnel otherwise categorized as Ground Operation Workers. These categories of workers have varying functions in the noisiest area at the ramp, and this exposes them to noise that could lead to hearing impairment or permanent ear damage. This study was focused on workers on the ramps at the international airport of a large US city. These workers also are known as ground handling staff, and these employees perform different tasks on the airline ramp, which include unloading luggage from the airline, picking up and moving luggage from the belt room, and to loading baggage onto the airline. This study was conducted using personal dosimeters which were calibrated before and after each sampling event out on four different employees over a period of four days and the collected data were downloaded to a personal computer for further analysis. From the results of this study, the highest noise exposures occurred on a ground operation worker 3 (GOW3) with an 8-hr TWA exposure of 85.6 dBA using OSHA PEL measurement specifications and this occurred on the fourth day of sampling which was a Saturday. The second highest exposure occurred on ground operation worker 1 (GOW1) on the fourth day with an 8-hr TWA exposure of 85.0 dBA. For ground operations worker 2 (GOW2) and ground operation worker 4 (GOW4), the highest exposure occurred on the second day with 79.8 dBA and 73.4 dBA as their time weighted averages, respectively. None of the workers exposures exceeded the OSHA permissible exposure limit of 90 dBA. The United States Navy uses the OSHA noise standard to evaluate noise exposure on ships and all Navy installations. According to University of South Florida institutional review Board, this study is categorized as a program evaluation that has no intervention with human subjects. The workers that participated in this study did so voluntarily.

An experiment was conducted to study earmuff wearers’ signal detection in noise performance and perceptions of comfort and acceptability with two amplitude-sensitive earmuffs as compared to their conventional counterparts. Passive and electronic amplitude-sensitive earmuffs were tested, represented by the EAR Ultra 9000 and the Peltor T7-SR, respectively. Directly comparable earmuffs, the EAR 2000 and Peltor H7A, were used as conventional controls. The effect of the Peltor T7-SR’s gain on noise exposure and the attenuation of all earmuffs was also assessed. Signal detection performance was assessed via masked threshold determination in three levels of pink noise (75, 85, and 95 dBA), using a digitized back-up alarm as the detection stimulus. A modified Hughson-Westlake procedure was used to obtain 10 trials for each earmuff under each noise level. Comfort and acceptability were investigated via questionnaire. Real-ear-at-threshold (REAT) attenuation measures were recorded at 500 and 1000 Hz to ensure consistent earmuff fitting and measurements were made of the effect of subjects’ Peltor T7-SR gain settings in each noise level using a KEMAR manikin. Results indicated that only the noise level significantly influenced subjects mean masked thresholds; masked threshold increased linearly with noise level. The lack of a significant earmuff main effect or interaction could have resulted from the step size used to present the stimulus, the noise type or levels used, or the number of experimental conditions/sessions. No earmuffs were judged significantly different in comfort or acceptability. Noise level and gain status (on vs. off) were found to influence the measures taken on the noise level under the Peltor T7-SR, but the increase in noise dose with the gain control on was small. The estimates of attenuation obtained were reasonable for the devices tested. / Master of Science

Auditory situation awareness (ASA) is essential for safety and survivability in military operations where many of the hazards are not immediately visible. Unfortunately, the Hearing Protection Devices (HPDs) required to operate in these environments can impede auditory localization performance. Promisingly, recent studies have exhibited the plasticity of the human auditory system by demonstrating that training can improve auditory localization ability while wearing HPDs, including military Tactical Communications and Protective Systems (TCAPS). As a result, the U.S. military identified the need for a portable system capable of imparting auditory localization acquisition skills at similar levels to those demonstrated in laboratory environments. The purpose of this investigation was to develop and validate a Portable Auditory Localization Acclimation Training (PALAT) system equipped with an improved training protocol against a proven laboratory grade system referred to as the DRILCOM system and subsequently evaluate the transfer-of-training benefit in a field environment. In Phase I, a systems decision process was used to develop a prototype PALAT system consisting of an expandable frame housing 32-loudspeakers operated by a user-controlled tablet computer capable of reproducing acoustically accurate localization cues similar to the DRILCOM system. Phase II used a within-subjects human factors experiment to validate whether the PALAT system could impart similar auditory localization training benefits as the DRILCOM system. Results showed no significant difference between the two localization training systems at each stage of training or in training rates for the open ear and with two TCAPS devices. The PALAT system also demonstrated the ability to detect differences in localization accuracy between listening conditions in the same manner as the DRILCOM system. Participant ratings indicated no perceived difference in localization training benefit but significantly preferred the PALAT system user interface which was specifically designed to improve usability features to meet requirements of a user operable system. The Phase III investigation evaluated the transfer-of-training benefit imparted by the PALAT system using a broadband stimulus to a field environment using gunshot stimulus. Training under the open ear and in-the-ear TCAPS resulted in significant differences between the trained and untrained groups from in-office pretest to in-field posttest. / Doctor of Philosophy / Auditory situation awareness (ASA) is essential for safety and survivability in military operations where many of the hazards are not immediately visible. Unfortunately, the Hearing Protection Devices (HPDs) required to operate in these environments can impede sound localization performance. Promisingly, recent studies have exhibited the ability of the human auditory system to learn by demonstrating that training can improve sound localization ability while wearing HPDs. As a result, the U.S. military identified the need for a portable system capable of improving sound localization performance at similar levels to those demonstrated in laboratory environments. The purpose of this investigation was to develop and validate a Portable Auditory Localization Acclimation Training (PALAT) system equipped with an improved training protocol against a proven laboratory grade system referred to as the DRILCOM system and subsequently evaluate the transfer-of-training benefit in a field environment. In Phase I, a systems decision process was used to develop a prototype PALAT system consisting of an expandable frame housing 32-loudspeakers operated by a user-controlled tablet computer capable of reproducing similar sounds as the DRILCOM system. Phase II used a within-subjects human factors experiment to validate whether the PALAT system could impart similar sound localization training benefits as the DRILCOM system. Results showed no significant difference between the two localization training systems at each stage of training or in training rates for the open ear and with two HPDs. The PALAT system also demonstrated the ability to detect differences in localization accuracy between listening conditions in the same manner as the DRILCOM system. Participant ratings indicated no perceived difference in localization training benefit but significantly preferred the PALAT system user interface which was specifically designed to improve usability features to meet requirements of a user operable system. The Phase III investigation evaluated the transfer-of-training benefit imparted by the PALAT system using a broadband stimulus to a field environment using gunshot stimulus. Training under the open ear and in-the-ear TCAPS resulted in significant differences between the trained and untrained groups from in-office pretest to in-field posttest.

Noise levels in modern industrial and military environments are constantly increasing, requiring the improvement of current hearing protection devices. The improvement of passive hearing protection devices lies in examining the performance of major contributors to reduction of noise attenuation. The finite element method can be used to fully explore single hearing protection (SHP) and double hearing protection (DHP) systems, and the major performance mechanisms can be observed numerically as well as visually in modern postprocessing software. This thesis focuses on developing and evaluating double hearing protection finite element models, and exploring the behavior mechanisms responsible for reduced noise attenuation. The double hearing protection model studied consists of an earmuff preloaded to a barrier covered to simulate human flesh, and a foam earplug installed inside a rigid cylinder designed to simulate the human ear canal. Pressure readings are taken at the bottom of the simulated ear canal assembly. Advanced finite element models are used to reconcile differences between the experimental and finite element results, and to investigate the behavior of the modeled system. The foam earplug material properties for the finite element model are required in the same shear state of stress and boundary condition configuration as the experimental DHP setup, therefore a novel material extraction method is used to obtain this data. The effects of radial compression preload on the earplugs are considered, and the resulting foam earplug shear material properties are input into the finite element DHP model where the effects of the updated foam material properties are observed. / Master of Science

An experiment was conducted to determine the effects of different acoustic characteristics of the testing environment on the measured attenuation of hearing protection devices (HPDs) when using a standard real-ear attenuation at threshold (REAT) protocol. In the experiment, three earmuffs and three earplugs were tested in two diffuse sound fields implemented in two different sound environments with different loudspeaker configurations. In the first case, the testing environment was reverberant, with frequency-specific reverberation time characteristics as specified in ANSI $3.19- 1974, "Method for the Measurement of Real-Ear Protection of Hearing Protectors and Physical Attenuation of Earmuffs" and with three loudspeakers, one in each principal plane of the room. In the other case, a diffuse sound field was established within an anechoic chamber (free-field), as permitted by ANSI S12.6-1984 "Method for the Measurement of the Real-Ear Attenuation of Hearing Protectors" using four loudspeakers, one at each vertex of a tetrahedron with the subject's head center position at the centroid. Each of the environments met the requirements of the applicable ANSI standard as well as the requirements of standards adopted by several foreign countries. The experimental design allowed a direct comparison of the testing environments (reverberant vs. free-field) permitted by the two aforementioned ANSI standards. Results indicate that for both earmuffs and earplugs, the environment in which a REAT evaluation is performed has a statistically significant impact on the results of the evaluation. These results have implications for ongoing standards development efforts not only in the United States but also abroad since the testing environments investigated in this research are either required or allowed by several international standards. These international standards include: International Standard ISO 4869-1981, Canadian Standard CSA Z94.2-M1984, British Standard BSI 5108:1983, and Swedish Standard SS 882151 (1981). The impact of outlier dismissal on the results of REAT tests of HPDs was also investigated and found to have minimal impact on the results obtained in this experiment. However, this result is most likely case-specific and it is doubted that any generalizations can be made concerning outlier tests and their impact on HPD evaluations. As a side issue, it was also determined that ear canal size is highly correlated with attenuation achieved using premolded earplugs with attenuation decreasing with increasing ear canal size. No consistent gender effects were found in the analysis, indicating that gender alone may not be an important factor in determining how much attenuation can be obtained with a given HPD. Finally, the lack of a significant trial effect points to the absence of a strong practice effect over the three trials of a REAT evaluation, at least for subjects who are highly practiced in the REAT procedures. / Master of Science

Orientador: João Candido Fernandes / Banca: Edson Antonio Capello Sousa / Banca: Andrea Cintra Lopes / Resumo: O objetivo desta pesquisa foi determinar os níveis de atenuação de Dispositivos de Proteção Auditivos (DPAs), usando um teste chamado Resposta Auditiva de Estado Estável (RAEE). O teste RAEE é um exame eletrofisiológico que usa elétrodos para captar a atividade elétrica do tronco encefálico, sem depender da resposta do indivíduo, eliminando a subjetividade, assim como aspectos ligados à atenção, tempo de resposta, níveis de audição, etc. Neste método foram avaliados dez indivíduos, por meio da RAEE, estimulando-se o sistema de audição, primeiro sem protetor e, subsequentemente, com dois tipos de protetores auditivos, a saber um de inserção intra-auricular outro circunauricular de uso comum no mercado. Os resultados evidenciaram valores inferiores àqueles expressos no Certificado de Aprovação: para o plug, uma diferença de 10,3 dB, e para a concha, 4,3 dB. Na repetição dos testes, encontrou-se uma boa repetitividade, com diferença entre zero e 5 dB para 75% das frequências testadas. / Abstract: The purpose of this research was to determine the levels of attenuation of Hearing Protection Devices (HPDs) using a test called Auditory Steady-State Response (ASSR). The ASSR test is an electrophysiological examination that uses electrodes to capture the electrical activity of the auditory nerve and the brainstem without depending on the individual's response, thus eliminating the subjectivity of personal factors such as attention, response time, hearing ability, etc. This paper presents the results of a ten test which evaluated the hearing threshold of individuals, by first stimulating the hearing system without a protector and subsequently with a hearing protector. The results of this study were lower than those expressed in the Certificate of Approval: to plug a gap of 10.3 dB and dB the ear mufflers. The repetition of tests found a good repeatability with a difference between zero and 5 dB for 75% of the frequencies tested. / Mestre

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-18Bitstream added on 2014-06-13T18:34:56Z : No. of bitstreams: 1 queiroz_jl_me_bauru.pdf: 1056571 bytes, checksum: 740ab85f7a95dbf39493eb3d2218a8b5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo desta pesquisa foi determinar os níveis de atenuação de Dispositivos de Proteção Auditivos (DPAs), usando um teste chamado Resposta Auditiva de Estado Estável (RAEE). O teste RAEE é um exame eletrofisiológico que usa elétrodos para captar a atividade elétrica do tronco encefálico, sem depender da resposta do indivíduo, eliminando a subjetividade, assim como aspectos ligados à atenção, tempo de resposta, níveis de audição, etc. Neste método foram avaliados dez indivíduos, por meio da RAEE, estimulando-se o sistema de audição, primeiro sem protetor e, subsequentemente, com dois tipos de protetores auditivos, a saber um de inserção intra-auricular outro circunauricular de uso comum no mercado. Os resultados evidenciaram valores inferiores àqueles expressos no Certificado de Aprovação: para o plug, uma diferença de 10,3 dB, e para a concha, 4,3 dB. Na repetição dos testes, encontrou-se uma boa repetitividade, com diferença entre zero e 5 dB para 75% das frequências testadas. / The purpose of this research was to determine the levels of attenuation of Hearing Protection Devices (HPDs) using a test called Auditory Steady-State Response (ASSR). The ASSR test is an electrophysiological examination that uses electrodes to capture the electrical activity of the auditory nerve and the brainstem without depending on the individual's response, thus eliminating the subjectivity of personal factors such as attention, response time, hearing ability, etc. This paper presents the results of a ten test which evaluated the hearing threshold of individuals, by first stimulating the hearing system without a protector and subsequently with a hearing protector. The results of this study were lower than those expressed in the Certificate of Approval: to plug a gap of 10.3 dB and dB the ear mufflers. The repetition of tests found a good repeatability with a difference between zero and 5 dB for 75% of the frequencies tested.

Os equipamentos de proteção individual devem ser utilizados após a implantação de medidas administrativas, de medidas de proteção coletiva, alterações de projeto ou em situações de emergência. Podem ser considerados como a última barreira entre um trabalhador e uma condição perigosa. A seleção destes equipamentos deve ser cuidadosa e este trabalho objetivou a criação de um programa de computador para auxiliar os profissionais responsáveis pelo processo de seleção de protetores auditivos, uma posterior comparação entre as saídas do programa com os equipamentos disponibilizados para os trabalhadores das empresas analisadas e uma análise crítica dos documentos obtidos das empresas. Foi efetuada uma revisão bibliográfica das metodologias de seleção de protetores auditivos, criando-se um fluxograma decisório, com pontos de interação com o usuário para a coleta de dados. Foram utilizados programas de prevenção de riscos ambientais de 7 empresas de mineração, identificadas as atividades cujos níveis de ruído se encontravam acima dos limites legais permitidos, determinando-se a necessidade ou não da utilização de protetores auditivos. Os dados foram introduzidos no programa, obtendo-se uma lista de equipamentos adequados para cada atividade selecionada. Compararam-se os equipamentos selecionados pelo programa com os equipamentos oferecidos pelas empresas, identificando-se as vantagens do programa. Observou-se também a baixa qualidade dos documentos emitidos pelas empresas que, em geral, não atenderam aos requisitos mínimos dispostos na legislação. Verificou-se que, quando selecionados corretamente, os equipamentos selecionados pelas empresas estavam contidos na lista de saída do programa, concluindo-se que o programa permitiu maior flexibilidade na escolha dos equipamentos de proteção auditiva, podendo se refletir em vantagens ergonômicas para os trabalhadores e econômicas para as empresas. / Personal protective equipment should only be used after engineering, administrative and work practices or in emergency situations. For this reason, PPE may be considered the last line of defense between workers and a hazardous situation. This work aims to create computer software to assist safety personnel in the PPE selection process, to compare the results produced by this software with the equipment provided by the companies when data from exposures were input and a critical analysis of the documents provided by the companies. A search for the PPE selection methods was conducted, generating a flowchart for hearing protector selection that was implemented in a web site. Data from risk management programs of 7 Brazilian mining companies were used as input to the software once the high risk of noise exposure activities were identified. A list of adequate equipment was then generated by the software and this list was compared to the list of equipments provided by each company. After a critical analysis the software advantages were found to be the higher flexibility in the choice of hearing protectors brought by the much larger list of adequate equipment. Additional advantages include the smaller amount of time spent looking for the correct choice and the ability to provide multiple choices of equipment for workers to choose from, which increases the comfort and thus the compliance to the PPE program. The quality of the documents provided by the companies was found to be low and lacking several requirements of Brazilian Law. The created software was found to be a useful tool, further testing and improvements are needed to increase its usability and to consolidate it as an asset to health and workplace safety professionals.