Compensation And Feedback Parameters Based On The Research And Implementation Of Sound Source Signal Processing Methods

According to the parametric acoustic array theory, the parametric loudspeaker can generate highly directional audible sound using the nonlinear effects of air. It’s a new type of audible sound source. Based on the analysis of the distortion of the existing signal processing method, a signal processing method based on compensation and feedback is proposed, and a theoretical model of this signal processing method is established. Its effectiveness is verified through simulation analysis. And then the compensation processing method is implemented on the DSP platform. Finally, the compensation processing method performance is tested by experiment.This paper carries out a detailed analysis of intermodulation distortion in single-sideband (SSB) modulation method of parametric loudspeaker. Clear the relationship between original audio signal and distortion in self-demodulated signal, input signal amplitude and the modulation index. A SSB compensation algorithm that can be implemented in multi orders is proposed in this paper to solve the distortion problem, in which some intermodulation distortion compensation items are introduced into the input signal to counteract the low-order intermodulation distortion items and reduce the high-order ones, and its analytical model is established by theoretical analysis. Its effectiveness is verified through simulation analysis. This paper focuses on the analysis of first and second order SSB compensation algorithm. And then clear the relationship between the distortion in SSB compensation algorithm, modulation index, compensation orders and input signal amplitude.Besides, the feedback processing method for the distortion of power amplifier and ultrasound transducer is proposed in this paper. Tracking the working status of power amplifier and ultrasound transducer through the introduction of feedback, the input of transducer can be stabilized by adjusting the input signal of amplifier in real time. To predict the power amplifier and the ultrasound transducer transfer function in real-time tracking process, this paper focuses on the feedback algorithm based on a linear function fitting and improved quadratic function fitting. Through simulation analysis, it is verified that the feedback algorithm can effectively reduce the input signal error of the ultrasound transducer. Then clear the relationship between the feedback algorithm error and the amplitude and frequency of the transfer function.Finally, in accordance with the theoretical analysis and simulation results, first order SSB modulation compensation algorithm is implemented on the ADSP-BF533platform. The system structure of parametric loudspeaker is proposed. Then the Hilbert transform method which is implemented by a finite impulse response filter is analyzed in this paper. And what’s more, the real-time delay processing method, the input signal interpolation processing method and carrier generating method are all proposed in this paper. Then the program flow and the DSP module initialization method are put forward. At the same time, this paper also set up the corresponding experimental test platform. The experiment results show that the SSB compensation algorithm proposed in this paper can reduce the intermodulation distortion of the SSB modulation significantly.