长阻抗管过渡过程对于测量声学参数的影响研究  

An Investigation on the Influence of Settling Process of Long Impedance Tube on the Measurement of the Acoustic Parameters

作　　者：周静雷[1] 沈勇[1] 邹健[1] 

机构地区：[1]南京大学声学研究所,近代声学国家重点实验室,南京210093

出　　处：《南京大学学报（自然科学版）》2005年第4期398-406,共9页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(10474046)

摘　　要：提出了用单传声器以扫频获得传递函数来精确测量长阻抗管末端试件声学参数的测量方法.用正弦信号代替随机信号作为测试信号,可以显著的提高测量精度.但是对于长阻抗管,因为过渡过程时间较长,所以要消除过渡过程的不利影响.首先从理论上证明了冲击响应与扫频测量过渡过程时间之间的关系,接着提出根据冲击响应用施罗德积分来计算过渡过程时间的方法,然后从理论上分析了过渡过程时间与试件声学参数之间的关系,最后对多种试件进行测试,确定了过渡过程时间同声学参数之间的定量关系.理论分析和实验结果都表明,长阻抗管过渡过程时间随着试件吸声系数的增加而减小.为了保证测量精度,需要合理设定测量系统的延迟时间,以避免过渡过程的不利影响.Introduces the sweeping method to obtain the transfer function for measuring the acoustic parameters of the sample at the end of the long impedance tube with a single microphone. A single microphone can eliminate the elaborate calibrating procedure and any error associated with phase-mismatching. Though the transfer function method using random signals as the test signal can get the measured results very fast, the results do not seem to be satisfying. By using sine wave to replace random signals, the measurement accuracy can be improved evidently. But a new problem occurs and it should be attached importance to. In application, when the sound source of the impedance tube starts to work, the standing wave field in the long impedance tube will tend to be stabilizad after the sound wave is reflected between the sound source and the samples for many times. This process is called the settling process, and the time which it takes is called the settling time (t-s). If the length of the tube is a bit long (For example the length of the tube is about 6.2 m, then it will take the sound wave 0.018 second to transfer from the sound source to the sample), t-s will be also long and can not be ignored. Because the theory of the transfer function method is based on the steady sound field, the negative influence of the settling process must be avoided to ensure the accuracy of the measurement. Firstly, this paper proves the relation between the impulse response and the settling time of the sweeping measurement. The settling time of the impulse response equals the one of the sine signal response. Secondly, a method using Schroeder integral to calculate the settling time from the impulse response is introduced. Using Schroeder integral has many advantages because it can avoid many insurmountable difficulties. Thirdly, the relation between the settling time and the acoustic parameters of the samples is analyzed in theory. The settling time tends to decrease with the in crease of the sound absorption coefficient. Finally, many sample

关 键 词：单传声器 传递函数法 过渡过程 测量 

分 类 号：O42[理学—声学]