Abel Sharon M, Boyne Stephen, Roesler-Mulroney Heidi
Individual Readiness Section, Defence Research and Development Canada, Toronto, Ontario, Canada.
Noise Health. 2009 Oct-Dec;11(45):199-205. doi: 10.4103/1463-1741.56213.
Conventional hearing protection devices result in decrements mainly in the ability to distinguish front from rearward sound sources. The aim of this study was to investigate the effect of wearing an earplug with advanced communications capability, in combination with an army helmet, on horizontal plane speaker identification. Ten normal-hearing male subjects were tested in a semi-reverberant sound proof booth under eight conditions defined by combinations of two levels of ear occlusion (unoccluded and occluded by the earplug) and four levels of the helmet (head bare and fitted with the helmet modified to give no, partial and full ear coverage). Percent correct speaker identification was assessed using a horizontal array of eight loudspeakers surrounding the subject at one meter. These were positioned close to the midline and interaural axes of the head, at ear level. The stimulus was a 75-dB SPL, 300-ms broadband white noise. Both degree of ear coverage and ear occlusion significantly determined outcome. Overall percent correct ranged from 93.6% (bareheaded) to 79.7% (full ear coverage) with the ears unoccluded, and from 83.4%-77.5% with ear occlusion. Both variables affected the prevalence of mirror image confusions for positions 30 degrees apart in front and back of the interaural axis. With ear occlusion, front given back errors were more likely than back given front errors, increasing with degree of ear coverage to 49% and 25.4%, respectively. These errors also increased with ear coverage with the ears unoccluded, but were similar. Both degree of ear coverage and ear occlusion significantly impacted horizontal plane speaker identification, particularly for sources close to the interaural axis. However, overall percent correct was higher than observed in a previous study with conventional and level-dependent hearing protection devices, using the same array.
传统的听力保护装置主要会降低区分前后声源的能力。本研究的目的是调查佩戴具有先进通信能力的耳塞并结合军用头盔对水平面扬声器识别的影响。10名听力正常的男性受试者在半混响隔音室中，在由两种耳塞堵塞程度（未堵塞和被耳塞堵塞）和四种头盔配置（头部裸露以及佩戴经改装可提供无耳部覆盖、部分耳部覆盖和完全耳部覆盖的头盔）组合定义的八种条件下进行测试。使用围绕受试者一米处的八个扬声器的水平阵列来评估扬声器识别的正确百分比。这些扬声器位于靠近头部的中线和双耳轴处，与耳部齐平。刺激声为75分贝声压级、300毫秒的宽带白噪声。耳部覆盖程度和耳塞堵塞程度均显著影响测试结果。在耳部未堵塞的情况下，总体正确百分比范围为93.6%（头部裸露）至79.7%（完全耳部覆盖），而在耳塞堵塞的情况下为83.4% - 77.5%。这两个变量都影响了在双耳轴前后30度位置处镜像混淆的发生率。在耳塞堵塞的情况下，前方声源误判为后方声源的错误比后方声源误判为前方声源的错误更常见，随着耳部覆盖程度的增加，分别增至49%和25.4%。在耳部未堵塞的情况下，这些错误也随着耳部覆盖程度的增加而增加，但两者相似。耳部覆盖程度和耳塞堵塞程度均显著影响水平面扬声器识别，特别是对于靠近双耳轴的声源。然而，总体正确百分比高于先前使用相同阵列对传统和与水平相关的听力保护装置进行的一项研究中的观察结果。
