A low cost loudspeaker array for personal audio with enhanced vertical directivity

Personal audio refers to the production of spatially distinct listening zones within a space that is shared by multiple people. This technology can enable each listener to hear their own desired material without affecting others, facilitate private communication in public spaces, or provide independent volume controls when people of different ages watch TV together. This is accomplished using loudspeaker array processing, and the performance of a given system is subject to practical limitations associated with the array, the zonal geometry and the reproduction environment. The directivity of typical line array designs is only controllable in the horizontal plane, with approximately monopole directivity in the vertical direction. This can reduce real-world performance through excitation of the reverberant sound field. To overcome this limitation a design is presented for an eight-channel line array of loudspeakers, with each loudspeaker designed to be directional in the vertical plane. The design uses inexpensive components and the USB audio protocol to lower the barrier to entry into personal audio research and development. In order to form sound zones, input signals must be processed using transfer responses between the array elements and the desired sound zones, and in keeping with the philosophy of cost reduction, two different methods for analytically approximating these responses are compared against anechoic measurements which are expensive to acquire.