0.1~20Hz低失真度激光活塞发声器的设计与实现

为实现次声频段传声器的准确校准,研制了低失真、低泄漏的激光活塞发声器。激光活塞发声器采用具有空气轴承和位移反馈控制的超低频振动台驱动的活塞-腔体组合获得低失真度的声压信号;采用气浮自对中技术的小间隙缸塞配合以及大体积的腔体设计,获得了低泄漏的活塞发声器。在0.1~20 Hz,声压波形总谐波失真低于0.8%,实现高达50 s的腔体泄漏时间常数,使其适用于更低频段的传声器校准。在0.1~20 Hz频率范围内,激光活塞发声器的测量不确定度不超过0.58 dB (k=2)。与耦合腔互易法、关联传声器法的比较结果表明,激光活塞发声器法获得的传声器灵敏度与其他方法之间具有很好的一致性。

Design of a precise laser pistonphone with low distortion operating from 0.1 Hz to 20 Hz

To calibrate infrasound microphone with high accuracy, a laser pistonphone with low harmonic distortion and low leakage was developed. In the pistonphone, a precise piston-chamber pairing is driven by an ultra-low-frequency electromagnetic vibrator with air bearings and displacement feedback loop, which results in the low distortion of sound pressure in the cavity. A small gap within the piston and its cylinder is realized with the technology of air-flotationcentring. Thus, the total harmonic distortion of infrasonic sound pressure was measured as low as less than 0.8% from 0.1 Hz to 20 Hz and the leakage time constant of the pistonphone was measured to be more than 50 seconds, which makes it very suitable for low frequency microphone calibration. The uncertainty analysis show that the uncertainty of the system is estimated to be less than 0.58 dB (k=2) when operating at the frequency from 0.1 Hz to 20 Hz. The experimental results show that the sensitivities of the microphone obtained from the developed laser-pistonphone have good agreements with the results from the reciprocity method and 'related microphones' method.