为了使可听噪声的时域结果直接应用于噪声评价中,根据声级计的基本原理和直流电晕放电产生可听噪声的随机性特点,叙述了将可听噪声时域测量结果转化为声压级的方法,即采用功率谱分析方法来计算可听噪声声压的有效值,同时实现对噪声信号...为了使可听噪声的时域结果直接应用于噪声评价中,根据声级计的基本原理和直流电晕放电产生可听噪声的随机性特点,叙述了将可听噪声时域测量结果转化为声压级的方法,即采用功率谱分析方法来计算可听噪声声压的有效值,同时实现对噪声信号进行时间计权、A计权及倍频分析等,从而实现了由时域数据获得频域声压级的目的。基于实验室内搭建的单点电晕放电可听噪声测试平台,获得了单点电晕放电产生的可听噪声的时域波形,将该方法与Labview噪声分析工具箱的分析结果进行对比,验证了本文方法的正确性。最后对单点电晕放电产生可听噪声的频域特性及声压级特性进行了分析。研究结果表明,单点直流电晕放电产生的可听噪声的声压级在可听的频率范围内(20 Hz^20 k Hz),随着电压增加而有所增加;电晕噪声在高频段(1 k Hz以上)内的A计权声压级相对较大。研究方法和所得结论可为对电晕放电产生可听噪声特性的深入研究奠定基础。展开更多
Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we...Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action.Thirteen young males performed isometric actions with the upper limb at different force levels.sEMG activities of the biceps brachii were recorded during the actions.Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions.sEMG activities were analyzed using the one-third band octave method,and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale.The results showed that the relationship could be expressed by a conic curve,and could be used to evaluate muscle fatigue during machine operation.展开更多
文摘为了使可听噪声的时域结果直接应用于噪声评价中,根据声级计的基本原理和直流电晕放电产生可听噪声的随机性特点,叙述了将可听噪声时域测量结果转化为声压级的方法,即采用功率谱分析方法来计算可听噪声声压的有效值,同时实现对噪声信号进行时间计权、A计权及倍频分析等,从而实现了由时域数据获得频域声压级的目的。基于实验室内搭建的单点电晕放电可听噪声测试平台,获得了单点电晕放电产生的可听噪声的时域波形,将该方法与Labview噪声分析工具箱的分析结果进行对比,验证了本文方法的正确性。最后对单点电晕放电产生可听噪声的频域特性及声压级特性进行了分析。研究结果表明,单点直流电晕放电产生的可听噪声的声压级在可听的频率范围内(20 Hz^20 k Hz),随着电压增加而有所增加;电晕噪声在高频段(1 k Hz以上)内的A计权声压级相对较大。研究方法和所得结论可为对电晕放电产生可听噪声特性的深入研究奠定基础。
文摘Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action.Thirteen young males performed isometric actions with the upper limb at different force levels.sEMG activities of the biceps brachii were recorded during the actions.Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions.sEMG activities were analyzed using the one-third band octave method,and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale.The results showed that the relationship could be expressed by a conic curve,and could be used to evaluate muscle fatigue during machine operation.
