A loudspeaker array control method for exciting multi-order acoustic modes in a cylindrical duct

The Spinning Mode Synthesizer(SMS) is a device that can generate specific spinning acoustic modes in a duct.A loudspeaker array control method for exciting multi-order acoustic modes,especially radial modes,has been studied.The multiple modes can be generated by simultaneously adjusting the amplitude and phase of each source.An axial multi-ring arranged artificial source array is used without optimizing the location of the sound source for a specific mode.The circumferential and axial positions of the sources are considered simultaneously in the control method.The linear relationships between source strengths and mode coefficients of the target multi-modes are established,and then the complex source strengths are obtained with the least-squares method.A high-order Spinning Mode Synthesizer is researched and design.The amplitudes and phases of the loudspeakers are controlled by a digital signal system to generate the target modes in a cylindrical duct.The experimental results show that single or multiple modes can be precisely controlled in the duct,and the signal-to-noise ratios of the mode coefficients are almost greater than 10 dB.