Objective assessment for the effect of hearing protectors, background noise levels, and backup alarm acoustic features on listeners' abilities to localize backup alarm signals in the horizontal dimension, as well as on their ability to detect backup alarm signals in the distance dimension, is lacking in the acoustics and safety literature. Accordingly, two research experiments were conducted for this dissertation. In the first experiment, the effect of seven hearing protectors, two background pink noise levels (60 dBA and 90 dBA), and two backup alarm signals (standard and spectrally-modified) on the ability of normal hearing listeners to localize backup alarm signals in the horizontal dimension was investigated. Results indicated that a diotic sound transmission earmuff significantly degraded localization accuracy as compared to all other hearing protectors and the open ear condition. In addition, no significant difference existed between the open ear condition and the other hearing protectors in localization accuracy in most of the conditions tested. However, the E-A-R/3M HiFiTM earplug was advantageous in localization performance since it provided a significantly higher percentage correct localization than the Moldex foam earplug, the diotic earmuff, and the dichotic earmuff in 90 dBA pink noise. As for main effects of the other independent variables, the 90 dBA pink noise significantly degraded localization performance as compared to the quiet condition of 60 dBA, and a spectrally-modified backup alarm significantly improved localization performance as compared to the standard (narrowband) backup alarm. Potential application of these results includes the revision of backup alarm standards. In addition, these results provide clear advice for safety professionals to avoid the application of diotic sound transmission earmuffs for workers if localizing backup alarms is important. In the first experiment, listeners' feeling of comfort for each hearing protector was assessed subjectively by using a comfort rating scale. In addition, a subjective assessment for listeners' confidence in their localization decisions was established. Results indicated no significant difference between the hearing protectors in terms of comfort. However, in terms of listeners' confidence in localization decisions, their confidence was significantly degraded when they were fitted with the diotic earmuff. By contrast, they showed significantly more confidence in their localization decisions when they were fitted with the E-A-R/3M HiFi™ earplug as compared to when they were fitted with the Moldex foam earplug, the E-A-R/3M Ultrafit™ earplug, and the Bilsom passive earmuff. In the second experiment, listeners' performance in detecting a stationary backup alarm signal, including both a standard (narrowband) and broadband (pulsed white noise) alarm, was determined while they were equipped with various passive and electronic hearing protection devices. Listeners' performance was quantified by detection distance, which was defined as the distance between the stationary backup alarm device and the position where the listener detected the backup alarm signal. The resultant data demonstrated that normal hearing listeners detected a standard (narrowband) backup alarm signal at significantly longer distances as compared to the broadband (Brigade™) backup alarm signal, thus indicating the earlier forewarning by the standard alarm. In addition, passive hearing protection devices characterized with high attenuation significantly reduced the detection distance. These results may be applied to assist safety professionals in selecting hearing protectors and backup alarm signals that provide on-foot workers with ample time to react to an approaching backing vehicle, thus improving their safety. / Ph. D.

Made available in DSpace on 2016-04-27T18:12:24Z (GMT). No. of bitstreams: 1 Ana Maria Pimenta da Fonseca.pdf: 566657 bytes, checksum: 4943537ba9730854c7867eec02d30707 (MD5) Previous issue date: 2007-10-10 / The goal of this study was to investigate and analyze the civil construction workers audiometric profile upon admission in the State of Bahia (Brazil) from 1999 to 2005. Methods: Audiometric tests (n=5702) were carried out among male workers (age range: 18 to 72) upon admission when applying for several job positions in 43 civil construction companies. Audiograms was classified into three groups: normal , indicating noise-induced hearing loss (NIHL) and other causes , and were later rated as to the presence/absence of audiometric notches. Results: Normal hearing thresholds were found in 3949 (69.3%) workers, 920 (16.2%) of them showed audiograms indicating NIHL, and other alterations were found in 833 (14.6%) subjects. Although 980 (17.2%) workers did not report noise exposure, 4722 (82.8%) subjects reported at least one year of such exposure. The use of hearing protection devices was reported by 2483 (43.5%) subjects in contrast with 3219 (56.0%) workers who did not use it. Workers exposed to chemicals totaled 1084 (19%) against 4618 (81%) nonexposed ones. Audiometric notches were found in 1684 (29.5%) subjects in the normal group, 919 (16.1%) subjects in the NIHL group and 774 (13.4%) subjects in the other causes group. Conclusions: The prevalence of audiometric alterations was found to be 30.7%, among which 16.1% indicated NIHL and 14.6% were rated as other causes . Increased age, more than 5 years of noise exposure, lack of use of hearing protection devices and exposure to chemicals were associated to the hearing losses found in the sample. The prevalence of audiometric notches in this population was 59.3%, of which 30.9% were unilateral and 28.4% were bilateral. Besides being associated to age, exposure time and job position, notches were more prevalent in the NIHL group and in the other causes group / O presente estudo tem como objetivo investigar e analisar o perfil audiométrico nos exames admissionais em trabalhadores da construção civil na Bahia, no período de 1999 a 2005. Método: Foram avaliadas 5702 audiometria admissionais de trabalhadores do gênero masculino, que faziam processo seletivo em 43 empresas da construção civil. A faixa etária estava entre 18 e 72 anos. Os trabalhadores realizaram exames pré-admissonais para as mais diversas funções da construção civil. Os audiogramas foram classificados em três grupos: normais, sugestivos de PAIR e outras causas. Posteriormente, também foram classificados segundo presença ou ausência de entalhe audiométrico. Resultados: 3949 (69,3%) trabalhadores apresentaram limiares dentro da normalidade, 920 (16,2%) apresentaram alteração sugestiva de PAIR e 833 (14,6%) trabalhadores apresentaram outras alterações. Dentre esses, 980 (17,2%) trabalhadores não relataram exposição a ruído e 4722 (82,8%) tinham tempo de exposição a ruído de, no mínimo, um ano. Quanto ao uso de protetor auricular (EPI), 2483 (43,5%) faziam uso e 3219(56,%) não faziam uso. Em relação à exposição a produtos químicos, 1084(19%) estavam expostos e 4618 (81%) não estavam expostos. O entalhe audiométrico esteve presente em 1684 (29,5%) trabalhadores do Grupo Normal, 919 (16,1%) no Grupo PAIR e 774 (13,4%) no Grupo Outros. Conclusões: A prevalência de alterações audiométricas foi de 30,7%, sendo 16,1% sugestivas de PAIR e 14,6% de outras causas. O aumento da idade, tempo de exposição a ruído superior a cinco anos, não uso de protetores e exposição a produtos químicos foram associados às perdas auditivas encontradas na população. A prevalência de entalhe audiométrico na população foi de 59,3%, sendo 30,9% unilateral e 28,4% bilateral. Os entalhes foram associados à idade, tempo de exposição e função exercida; além de ocorrerem mais nos Grupos PAIR e Outros