Design and implementation of a car cabin personal audio system

The car cabin is extensively used as a listening environment for various audio programs, such as music, video soundtrack, navigation system instructions, telecommunications, and warning sounds. Due to this proliferation of audio sources and the different requirements of the different occupants of a car, there is a desire to implement personalized rear-seat entertainment. This paper investigates a method of generating two independent listening zones-one close to the front headrests and one close to the rear headrests-without the use of headphones. Simulations are conducted to understand the physical limits on generating personal listening zones within a car cabin-sized enclosure, and two loudspeaker array geometries are proposed to provide control over the full audio bandwidth. At low frequencies the four standard car audio loudspeakers are used and at higher frequencies an array of phase-shift loudspeakers mounted at the headrests is used. In the context of these two arrays a comparison between acoustic contrast and least-squares optimization strategies is presented. Finally a real-time implementation of the proposed personal audio system in a car cabin is described and its performance is shown to be consistent with the simulation results.