Study Of Automatic Calibration Device Of The Sound Field And Related Experiments

Sound field calibration is a necessary method to determine acoustic characteristics of acoustic laboratories, like the anechoic room and the reverberation room. Due to the low detection efficiency, accuracy and reliability of the calibration of the sound field, the accurate and efficient methods to calibrate the acoustic laboratory, and the automatic calibration device are urgently needed. Based on the JJF1147-2006 and ISO3745-2012 about the calibration of the sound field, this paper studies the methods to calibrate the acoustics laboratories automatically, and develops the automatic calibration device, and designs the calibration software and analyses the calibration parameters of the sound field. It is completed by the following sections:The first section, it proposes the methods to calibrate the sound field of the acoustic laboratories automatically. Through studying the accuracy of test results with different test signals in different measurement methods, it determines the sound center of a sound source, and determines the distribution of the sound field in the anechoic room. It is convenient to optimize the scattering factors of the sound field,and to improve the characteristics of the free field in the anechoic room.The second section, it designs the automatic calibration device of the sound field. The device includes the standard sound source with stable characteristics in high frequencies, the drive system, the drive control system, and the mechanical structure which can achieve the transmission automatically. It can achieves the microphone moving automatically in the sound field. The signal generation, signal acquisition and signal analysis system can realize the occurrence of sound source signals, the acquisition of the signals and the analysis of the data.The third section, it develops the calibration software of the sound field.Through PC/PLC communication port setting, and PLC control and parameter setting,and PULSE control and the sound source control, and microphone motion control,and the microphone location setting, it can control the hardware automatically, andcollect the data, store the data, display the data and other functions.The fourth section, it studies calibration parameters of the sound field through the automatic calibration method, and the calibration software and the automatic calibration device in the sound field. Firstly, it analyses the factors which can affect the calibration of the sound field, like the radiated noise of the transmission system,and the stability of sound source in the sound field. Then it analyses the calibration parameters with different sound source signals in different measurement methods according to JJF1147-2006 and ISO3745-2012. Finally, it analyses the calibration parameters with different sound source signals in different chosen distances under a certain measurement path. It is found that, the characteristics of the sound field are almost the same, when the endpoint is 0.57 meters away from the sound-absorbing wedge, and the endpoint is 0.75 meters away from the sound-absorbing wedge. So the distance between the endpoint and sound-absorbing wedge is not less than 0.75 meters specified in standards are worth further research. When the starting point is between 0.07 meters and 0.5 meters, almost all of the free field ranges meet the requirements of the standards, so the starting point is at 0.5 meters specified in standards are worth further research.