Design Of Directional Loudspeaker And Its Application In Subregional Sound Management In Cars

In order to realize the sub-regional sound field control in the vehicle and build a friendly interior acoustic environment,this paper designs digital directional speakers based on the principles of parametric array acoustics and digital speakers.Researches have been carried out on suppressing the harmonic distortion produced by selfdemodulation on the digital speaker platform by combing digital loudspeaker theory and modulation algorithm,and threshold filtering algorithm has been proposed.This paper has tested the directivity of the digital speaker,and analyzes the audible sound field formed by the digital speaker in the car through simulation.It shows that the digital directional speaker can realize the sound management in the car by region and provide drivers and passengers comfortable acoustic environment.Aiming at the directivity of the loudspeaker,in order to achieve the regional control of the acoustic environment in the car,this paper uses the principle of non-linear acoustics,combined with the parametric array speaker theory,and uses the high directivity of ultrasound to modulate the audible sound signal onto the ultrasound carrier signal Sound generation;Aiming at the problem of harmonic distortion in parametric array speakers,a modulation algorithm suitable for digital speakers is proposed in combination with a double-sideband modulation algorithm and a bit group control method,and the influences of the existing modulation coefficients for harmonic distortion and analysis are discussed.In this paper,a fully digital speaker array is designed as a directional speaker implementation platform,eliminating the need for hardware equipment and software processing modules required for A / D conversion and D / A conversion.Aiming at the control problem of loudspeaker array,this paper designs a bit group control method based on the number of transducers.By controlling the switch of the transducer to control the change of the sound pressure amplitude,the loudspeaker can be controlled with minimal resources.Aiming at the noise problem introduced by digital control,this paper designs and verifies the noise filtering algorithm.The experimental results show that the noise reduction effect is good.An acoustic transfer model is established based on the Berktay far-field solution,and the near-field solution of the speaker is deduced.The modulated signal is normalized to generate a pre-processed distortion signal.The ARM STM32F429IGT6 chip was selected as the hardware development platform,and the transducer array layout design and drive hardware circuit design were independently completed.Experiments were performed using single-frequency sound signals and synthesized sound signals respectively,and the influence that the number of digital speaker transducers on the sound quality is tested.The effect of resolution is tested on the modulation coefficient of the DSB modulation algorithm transplanted on the digital speaker.The directivity test of the built digital directional speaker platform is performed to test the sound field of the speaker in the near-field environment.The experiments show that the speaker still has good directivity in the near field.The environment model of the sound field in the car is established,and the area of the sound field in the car is divided.The sound signals of the digital directional loudspeaker in the bright area and the dark area are analyzed and calculated,and the result shows that digital directional loudspeaker can achieve regional acoustic management in the car.