 In practical engineering applications, accurate measurement of the sound field of parametric array loudspeakers is very important for the design and development of the system. The additional difference frequency electrical signal caused by the nonlinear distortion of the microphone inevitably appears in the measurement results, this part of the signal has the same frequency as the real difference frequency sound signal, but does not exist in the real acoustic field of the air, and it is called spurious sound. In the measurement process of parametric array loudspeakers, spurious sound is a key factor, directly related to the accuracy of the measurement results. Spurious sound mainly comes from two aspects, one is due to the nonlinear effect of the microphone preamplifier circuit, and the other is due to the radiation sound pressure on the surface of the transducer. It has been proven that the spurious sound generated by sound radiation pressure is not the main contribution in the measurement system. Since the acoustic filter is crucial for the accurate measurement of the parametric array loudspeaker, the near-field measurement of the difference frequency sound signal of the parametric array loudspeaker is a complex issue that has received much attention in recent years. In the near field, due to the high sound pressure level of the ultrasonic primary wave, the spurious sound is much larger than the difference frequency sound signal generated by the parametric array loudspeaker, and a filter must be adopted to obtain the real sound frequency signal. In the far field with the attenuation of the ultrasonic primary wave, the demodulated sound frequency signal can be obtained directly by using a microphone. In actual measurements, there are mainly two methods to avoid the influence of spurious sound. One is to increase the measurement distance. The second is to use acoustic filters to filter out ultrasound, which can be achieved by using specific acoustic structures or materials to reduce the amplitude of ultrasound in the measurement system, thereby reducing the influence of spurious sound. This chapter first presents a review of the current measurement techniques in parametric arrays. On this basis, detailed explanations are given for the cylindrical ultrasonic filter and the phononic crystal filter measurement techniques, and experimental studies are carried out on the impact of four main parameters on the measurement of parametric arrays.

Measurement of Parametric Array Loudspeakers

章节
发表日期：

2025年

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Jun Yang,
Peifeng Ji

摘要

In practical engineering applications, accurate measurement of the sound field of parametric array loudspeakers is very important for the design and development of the system. The additional difference frequency electrical signal caused by the nonlinear distortion of the microphone inevitably appears in the measurement results, this part of the signal has the same frequency as the real difference frequency sound signal, but does not exist in the real acoustic field of the air, and it is called spurious sound. In the measurement process of parametric array loudspeakers, spurious sound is a key factor, directly related to the accuracy of the measurement results. Spurious sound mainly comes from two aspects, one is due to the nonlinear effect of the microphone preamplifier circuit, and the other is due to the radiation sound pressure on the surface of the transducer. It has been proven that the spurious sound generated by sound radiation pressure is not the main contribution in the measurement system. Since the acoustic filter is crucial for the accurate measurement of the parametric array loudspeaker, the near-field measurement of the difference frequency sound signal of the parametric array loudspeaker is a complex issue that has received much attention in recent years. In the near field, due to the high sound pressure level of the ultrasonic primary wave, the spurious sound is much larger than the difference frequency sound signal generated by the parametric array loudspeaker, and a filter must be adopted to obtain the real sound frequency signal. In the far field with the attenuation of the ultrasonic primary wave, the demodulated sound frequency signal can be obtained directly by using a microphone. In actual measurements, there are mainly two methods to avoid the influence of spurious sound. One is to increase the measurement distance. The second is to use acoustic filters to filter out ultrasound, which can be achieved by using specific acoustic structures or materials to reduce the amplitude of ultrasound in the measurement system, thereby reducing the influence of spurious sound. This chapter first presents a review of the current measurement techniques in parametric arrays. On this basis, detailed explanations are given for the cylindrical ultrasonic filter and the phononic crystal filter measurement techniques, and experimental studies are carried out on the impact of four main parameters on the measurement of parametric arrays.