Research On Calibration Method And Device Of Car Whistle Snapping System

The car whistle snapping system measures the amplitude and phase difference of the sound signal that reaches the microphone array,and displays the distribution of the sound field and sound source to the user in the form of a photo.It is suitable for law enforcement systems that prohibit the whistle on urban roads.However,the technical indicators and accuracy of the car whistle snapping system currently lack a unified calibration specification,so it is necessary to conduct a calibration study on the car whistle snapping system.This article focuses on the calibration method and calibration device of the car whistle capture system based on the principle of beamforming.Based on the product parameters provided by the major manufacturers of domestic and foreign car whistle snapping systems,positioning errors,spatial resolution and sound pressure levels are proposed as its main calibration parameters,and the definitions are made.The calibration environment and difference frequency signals are defined.The dynamic range of the sound pressure level was selected.The sound source localization of the beamforming algorithm with a specific array shape is simulated,the influence of different parameter variables on sound source localization recognition is studied,and the corresponding calibration method is proposed.The calibration device of the car whistle snapping system was designed,and the hardware components were selected and designed according to the index requirements,and the software program was developed for the host computer program interface.The hardware structure of the designed calibration device is mainly composed of standard sound source,data acquisition card,standard microphone and sound level calibrator.The standard sound source is similar to the point sound source.The data acquisition card is responsible for the collection of sound waves and sound signals in a specific frequency band.The standard microphone can be used to calibrate the sound pressure level after being corrected by the sound level calibrator.The program-controlled computer and the data acquisition card are connected by USB to realize the function of program control.A mainstream car whistle snapping system product on the market was calibrated in the indoor total anechoic room environment and the outdoor road by using the designed calibration method and calibration device.Indoor positioning error is(100-160)mm,horizontal spatial resolution is(238-530)mm,vertical spatial resolution is(519-950)mm,outdoor positioning error is(700-1200)mm,and the maximum deviation of sound pressure level is not more than 5 dB.At the same time,the expanded uncertainty of the calibration device system is calculated to be 0.812 dB(k=2).The feasibility of the device and method was verified.