Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military,it is required to be considered to accurately predict earmuff attenuation.Besides unwanted air l...Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military,it is required to be considered to accurately predict earmuff attenuation.Besides unwanted air leakage,under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios(SNRs)and balance between attenuation and speech intelligibility.This work is to develop an improved lumped parameter model(LPM)to predict earmuff attenuation with consideration of air leakage.Air leakage paths are introduced into conventional LPM without air leakage,and air leakage path impedance is analytically described by Maa’s microperforated tube impedance.Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM.Finally,the validity of improved LPM is verified experimentally.The results indicate that the improved LPM can predict earmuff attenuation with air leakage,and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.展开更多
This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at thresho...This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at threshold (REAT) under freefield condition. The five devices were examined singly, and four of them in combination. The performance of double hearing protection (earplug plus earmuff)were investigated experimentally using the same method for a number of combinations. All tests were conducted on 7 subjects, and two replications per subject. The obtained data of the earmuffs tested show that earmuff (A) posscsses the lowest attenuation and is characterized by highest standard deviation. On the other hand, the foam plug provides the higher attenuation and the lower standard deviation. When the foam plug was combined with either carmuff (B or C) an improvement of attenuation was similar, i. e. the choice of earmuff is not important. This combination yields higher attenuation than that produces for either device alone, but does not simply yield overall attenuation equal to the sum of the individual of each device. However, when situation was reversed, the combination of either earplug (foam or molded) with single earmuff yields variation in attenuation below 2 kHz. At and above 2 kHz, the combination results were comparcd to the bone conduction limits which was reported by different authors. At these frequencies, all tests of plug plus earmuff combinations that were studied provided attenuation approximately equal to the bone conduction limits of human skull. Finally, the attenuation estimates derived in this study werc less than comparable data published by the respective manufacturers.展开更多
为研究冲击波作用下的人耳动态响应特性,设计并开展基于某单兵火箭类武器发射环境的有/无佩戴护听器装置试验研究。在分析发射冲击波特性的基础上,设计制作人耳测试装置模型,形成耳内冲击波防护试验测试方法。通过在射手位置处布设人耳...为研究冲击波作用下的人耳动态响应特性,设计并开展基于某单兵火箭类武器发射环境的有/无佩戴护听器装置试验研究。在分析发射冲击波特性的基础上,设计制作人耳测试装置模型,形成耳内冲击波防护试验测试方法。通过在射手位置处布设人耳测试装置模型以获取人耳内压力-时间变化曲线,并采用超压传感器测量对比位置处的自由场冲击波压力。利用小波分析法对测到的数据进行分析,对比分析2种发射冲击波安全限值的评价方法。研究结果表明:发射时的高声强冲击波具有不稳定性,超压峰值高,持续时间短,具有多个脉冲;高声强冲击波频带宽,成分复杂,有明显的低频率高声压特性;无护听器装置时耳内压力有所增强;佩戴护听器装置后可大幅度削弱冲击波对人耳的作用,正射手右耳超压峰值削弱95.7%、声压级峰值削弱14.8%;改进后的国家军用标准GJB 2A—1996“常规兵器发射或爆炸时脉冲噪声和冲击波对人员听觉器官损伤的限值”和美军标MIL-STD-1474E“Department of defense design criteria standard noise limits”中AHAAH模型2种方法得到的单日允许射击数范围接近,对佩戴护听器装置后的冲击波测量曲线评估的方法是可行的。研究结果可为单兵火箭类武器发射冲击波测试系统优化及改进提供理论基础和实践指导。展开更多
为了滤掉有害的环境噪声,研究一种个人噪声防护耳罩。应用频域归一化X滤波最小均方(Filtered-X NLMS)算法的单点频变步长特性,结合定点DSP(Digital Signal Processor)处理器,设计出适用于有源消噪耳罩的单通道自适应反馈式结构,自适应...为了滤掉有害的环境噪声,研究一种个人噪声防护耳罩。应用频域归一化X滤波最小均方(Filtered-X NLMS)算法的单点频变步长特性,结合定点DSP(Digital Signal Processor)处理器,设计出适用于有源消噪耳罩的单通道自适应反馈式结构,自适应算法的良好降噪效果在仿真实验中得到验证。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11934009 and 11874216)。
文摘Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military,it is required to be considered to accurately predict earmuff attenuation.Besides unwanted air leakage,under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios(SNRs)and balance between attenuation and speech intelligibility.This work is to develop an improved lumped parameter model(LPM)to predict earmuff attenuation with consideration of air leakage.Air leakage paths are introduced into conventional LPM without air leakage,and air leakage path impedance is analytically described by Maa’s microperforated tube impedance.Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM.Finally,the validity of improved LPM is verified experimentally.The results indicate that the improved LPM can predict earmuff attenuation with air leakage,and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.
文摘This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at threshold (REAT) under freefield condition. The five devices were examined singly, and four of them in combination. The performance of double hearing protection (earplug plus earmuff)were investigated experimentally using the same method for a number of combinations. All tests were conducted on 7 subjects, and two replications per subject. The obtained data of the earmuffs tested show that earmuff (A) posscsses the lowest attenuation and is characterized by highest standard deviation. On the other hand, the foam plug provides the higher attenuation and the lower standard deviation. When the foam plug was combined with either carmuff (B or C) an improvement of attenuation was similar, i. e. the choice of earmuff is not important. This combination yields higher attenuation than that produces for either device alone, but does not simply yield overall attenuation equal to the sum of the individual of each device. However, when situation was reversed, the combination of either earplug (foam or molded) with single earmuff yields variation in attenuation below 2 kHz. At and above 2 kHz, the combination results were comparcd to the bone conduction limits which was reported by different authors. At these frequencies, all tests of plug plus earmuff combinations that were studied provided attenuation approximately equal to the bone conduction limits of human skull. Finally, the attenuation estimates derived in this study werc less than comparable data published by the respective manufacturers.
文摘为研究冲击波作用下的人耳动态响应特性,设计并开展基于某单兵火箭类武器发射环境的有/无佩戴护听器装置试验研究。在分析发射冲击波特性的基础上,设计制作人耳测试装置模型,形成耳内冲击波防护试验测试方法。通过在射手位置处布设人耳测试装置模型以获取人耳内压力-时间变化曲线,并采用超压传感器测量对比位置处的自由场冲击波压力。利用小波分析法对测到的数据进行分析,对比分析2种发射冲击波安全限值的评价方法。研究结果表明:发射时的高声强冲击波具有不稳定性,超压峰值高,持续时间短,具有多个脉冲;高声强冲击波频带宽,成分复杂,有明显的低频率高声压特性;无护听器装置时耳内压力有所增强;佩戴护听器装置后可大幅度削弱冲击波对人耳的作用,正射手右耳超压峰值削弱95.7%、声压级峰值削弱14.8%;改进后的国家军用标准GJB 2A—1996“常规兵器发射或爆炸时脉冲噪声和冲击波对人员听觉器官损伤的限值”和美军标MIL-STD-1474E“Department of defense design criteria standard noise limits”中AHAAH模型2种方法得到的单日允许射击数范围接近,对佩戴护听器装置后的冲击波测量曲线评估的方法是可行的。研究结果可为单兵火箭类武器发射冲击波测试系统优化及改进提供理论基础和实践指导。
文摘为了滤掉有害的环境噪声,研究一种个人噪声防护耳罩。应用频域归一化X滤波最小均方(Filtered-X NLMS)算法的单点频变步长特性,结合定点DSP(Digital Signal Processor)处理器,设计出适用于有源消噪耳罩的单通道自适应反馈式结构,自适应算法的良好降噪效果在仿真实验中得到验证。
