The Design of Personal Audio Systems for Speech Transmission Using Analytical and Measured Responses

Personal Audio systems can be used to provide information and entertainment content in public spaces. Limitations in array directivity mean that speech information intended for a target region may remain intelligible elsewhere. This compromises privacy for target listeners and could prove distracting or annoying to passive listeners nearby. A system has previously been proposed whereby the intelligibility of this leaked speech is reduced by radiating an artificial masking signal into the dark zone; this masking signal has been optimised to minimise the potential for annoyance whilst achieving a predefined level of intelligibility in each zone, but only free-field responses were considered. In practice, systems located in public spaces will be adversely affected by noise and reverberation. This detriment to system performance can be quantified using engineering measures such as acoustic contrast, although the perceived performance as evaluated by users does not necessarily correspond. The present paper explores the effect of using analytical and measured transfer responses on speech intelligibility and system optimisation using a practical example of a personal audio system in a room.