An active headrest for personal audio

There is an increasing need for personal audio systems, which generate sounds that are clearly audible to one listener but are not audible to other listeners nearby. Of particular interest in this paper are listeners sitting in adjacent seats in aircraft or land vehicles. Although personal audio could then be achieved with headsets, it would be safer and more comfortable if loudspeakers in the seat headrests could be actively controlled to generate an acceptable level of acoustic isolation. In this paper a number of approaches to this problem are investigated, but the most successful involves a pair of loudspeakers on one side of the headrest, driven together to reproduce an audio signal for a listener in that seat and also to attenuate the pressures in the adjacent seat. The performance of this technique is investigated using simple analytic models and also with a practical implementation, tested in an anechoic chamber and a small room. It is found that significant attenuations, of between 5 and 25 dB, can be achieved in the crosstalk between the seats for frequencies up to about 2 kHz. (c) 2006 Acoustical Society of America.