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寻求不依赖于实验室标准传声器的灵敏度而直接溯源至国际单位制基本单位的声压量值复现技术是声学计量的长期目标,对声压量值摆脱实物基准具有重要意义,激光多普勒测速技术是实现这一目标的有效途径.以行波管内平面波声场为测量对象,建立无固定频移的激光多普勒测速系统,采用光子相关光谱分析法解调多普勒信号,获得声管内示踪粒子的振动速度,根据平面波声压与质点振动速度的线性关系,复现声管测量点处的声压.以工作标准传声器的测量结果为参考,评估测量方案的可行性和测量结果的准确性,分析影响测量准确性的主要因素.测量结果表明,声波频率为315Hz,声压级在100dB~110dB范围内间隔1dB变化时,测量偏差小于0.5dB;声压级为105dB,声波频率为315,400,500,800Hz时测量偏差小于0.3dB.
It is of long-term goal to seek acoustical metrology to find out the sound pressure value recurring technology that is traceable directly to the basic unit of the international system of units without depending on the sensitivity of the laboratory-standard microphones. It is of great importance to get rid of the physical reference of the sound pressure. Laser Doppler Tachometer technology is an effective way to achieve this goal.With the plane wave field in the traveling wave tube as measuring object, a laser Doppler velocimetry system with no fixed frequency shift is established, the Doppler signal is demodulated by photon correlation spectroscopy, According to the linear relationship between the sound pressure of the plane wave and the vibration velocity of the particle, the sound pressure at the sounding point is reproduced. Taking the measurement result of the working standard microphone as a reference, the feasibility of the measurement scheme and the result of the measurement are evaluated Accuracy and analysis of the main factors affecting the accuracy of the measurement.The measurement results show that when the sound frequency is 315Hz and the sound pressure level is within the range of 100dB ~ 110dB, the measurement deviation is less than 0.5dB, the sound pressure level is 105dB, the sound frequency is 315,400,500,800Hz measurement deviation less than 0.3dB.