本科毕业论文-市售护耳器实际降噪值评估.doc

学学 号：号：201095110124 毕毕 业业 论论文文 graduate thesis 论文题目：市售护耳器实际降噪值评估论文题目：市售护耳器实际降噪值评估 2015 年年 06 月月 02 日日 摘 要 - 摘摘 要要 目的：收集企业常用的 6 种耳塞，对 6 名女性志愿者进行听阈测试，通过 对各种耳塞的各频段降噪值测量，评估护耳器的实际 a 声级降噪值，对护耳器 的实际降噪效果进行评价，为建设项目职业病危害评价中护耳器的防护效果评 价和企业护耳器选用提供有益的参考。 方法：本文选择双耳气导听阈0.05 0.988.930.05 华北理工大学公共卫生学院 -13- 由表 3-10 可知，耳塞的实际 a 声级降噪值与 snr 值之间没有明显的关联 性，与 nrr 值之间有一定的关联性。 讨 论 -14- 4 讨论 目前评价耳塞降噪效果常用的是 snr、nrr 值这两个指标，snr 值和 nrr 都是基于粉红噪声谱而计算的11,粉红噪声指声压的功率谱密度与频率成 反比的噪声，其能量从低频向高频不断衰减。近年有学者14对耳塞的频谱特征 进行了研究，提出了不同耳塞具有最优防噪频段。有关用真耳听阈法来估计耳 塞的实际 a 声级降噪值的情况，目前尚未见报道。 本研究利用纯音气导听阈测听法对受试者裸耳和分别佩戴 6 种耳塞时的听 阈进行测试，得到耳塞的实际 a 声级降噪值，由表 3-8 和表 3-9 可知，各种耳 塞的实际 a 声级降噪值与由 snr 值或 nrr 值估计的 a 声级降噪值比较，差 异均具有统计学意义（p0.05） ，并且实验得到耳塞的实际 a 声级降噪值比由 snr 值或 nrr 值估计的 a 声级降噪值要高。可能的原因有：本实验是用纯 音测定戴耳塞前后的听阈，而 snr 值和 nrr 值是以粉红噪声为背景测得的， 并且在测试过程中加入了掩蔽。耳塞在应用过程中可能存在一个保护率的问 题由于本实验方法比较新颖，在之前的研究中未被提及，在设计、实施和计 算过程中有些地方还不够准确和完善。 理论上耳塞的 snr、nrr 值越大，耳塞的防噪效果就越好。但本研究结 果表明耳塞的实际 a 声级降噪值并不是随着 snr 值的增加而增加。可能的原 因为： 26 号耳塞都是泡棉耳塞，其降噪值的差别主要取决于耳塞的形状。3 号 耳塞 1100 子弹型耳塞和 5 号耳塞 ear 312-1250 earsoft 高降噪子弹型耳塞的 降噪效果较好，因为它是子弹型轮廓设计比较贴合人的耳道形状，佩戴比较舒 适，实际应用中职业人群在佩戴时会比较接近标准佩戴，因此能取得较好的降 噪效果。 2 号耳塞 ear 312-1213 class 圆柱型耳塞和 4 号耳塞 ear 311-1126 classic superfit 带标记圆柱型带线耳塞均为圆柱型，比较不容易戴到耳道的深处且容 易弹出会影响耳塞的实际降噪效果，可能由此导致 snr 值为 29db 的 2 号耳塞 的实际降噪效果与 snr 值为 25db 的 1 号耳塞的实际降噪效果区别不大，snr 值为 33db 的 4 号耳塞的实际降噪效果反而低于 snr 值为 31db 的 3 号耳塞的 实际降噪效果。 6 号耳塞 ear 318-1005 push ins 免揉搓泡棉带线耳塞虽然佩戴方便无需揉 搓，但是佩戴时会有疼痛感因此在实际应用中不容易正确佩戴，导致降噪效果 下降，出现其 snr 值虽然很高但是降噪效果反而不好的现象。 本研究结果表明，随着 nrr 值的增加，耳塞的实际 a 声级降噪值也随之 讨 论 -15- 增 华北理工大学公共卫生学院 -16- 加，说明用 nrr 值来估计耳塞的防噪效果可能更贴近耳塞在实际应用中 能够达到的防噪效果。 结 论 -17- 5 结论 实验得到的实际 a 声级降噪值比由耳塞的 snr 值和 nrr 值估计的实际 a 声级降噪值要高；用 nrr 值来评价耳塞的防噪效果更贴近耳塞的实际应用。 参考文献 -18- 参考文献 1 王福军,王国庆,牟学军.工业企业噪声污染现状及治理措施j.黑龙江环境通 报,2001,25(3):41-42. 2 杨震宇,刘移民.噪声健康效应研究进展j.中国职业医学,2006,33(3):217-219. 3 邱毅,杨超敏.职业性噪声聋防治研究进展j.应用预防医学,2012,18(1):59-62. 4 picrd m, gi rard sa, simard m, et al. association of work-related accidents with noise exposure in the work place and noise-induced hearing loss based on the experience of some 240,000 person-years of observationj.accident analysis he wondered how in the world he came to belong there. indeed his penning and publishing this essay caused his excommunication from high society and also caused him a lot of legal trouble. the legal trouble came as a result of the fact that he was speaking out against the government. i like to reference such texts from time to time as an example both of the fact that history does repeat itself and that this world is not so big that what applies to one society does not in any way touch another society. on a much smaller scale,emersons essay affects me very deeply. not as an urging to become self reliant im nothing if not that! in his text he expounds on the idea that one must give their life a purpose. and that is the true topic of this entry. these last four years have been so easy: teach for a grand total of six hours a week, and the rest of my time is mine. since ive been here i have been tasked with nothing more challenging than learning my students names and figuring out what to do with them for the brief time each week that i stand in front of them. i do not consider the challenges of learning to live here part of a purposeful life. i consider those issues existential in nature. one of the problems with my life in america was that i felt it had no purpose. i went to work every day and even did what i could to make my colleagues work lives easier, but i simply could not digest the fact that that was my sole purpose in life. with no family to support, i was the sole beneficiary of my employment: the paycheck, the benefits, the incentives and the rewards were mine alone. not much of a purpose in being self-serving, is there? while i was a student, i felt i was leading a purposeful life. learning new things, broadening my horizons, expanding my life e