Design and evaluation of personal audio systems based on speech privacy constraints

Personal audio refers to the generation of spatially distinct sound zones that allow individuals within a shared space to listen to their own audio material without affecting, or being affected, by others. Recent interest in such systems has focussed on their performance in public spaces where speech privacy is desirable. To achieve this goal, speech is focussed towards the target listener and a masking signal is focussed into the area where the target speech signal could otherwise be overheard. An effective masking signal must substantially reduce the intelligibility in this region without becoming an annoyance to those nearby. To assess these perceptual requirements, listening tests were carried out using two examples of loudspeaker arrays with different spatial aliasing characteristics, to determine the impacts of different masking signal spectra on speech intelligibility and subjective preference. The results of these tests were used, alongside objective and subjective metrics, to form a design specification for private personal audio systems.