Sound masking for achieving speech privacy with parametric acoustic array speaker

Speech privacy in open spaces is becoming increasingly important in various situations. Although measures such as the use of sound partitions are already used in many cases, measures that mask speech by emitting sounds have also been considered. A method of masking meaningful speech with meaningless noise would be valuable. Because of this, previous studies have investigated the ability of meaningless steady noise to mask speech and consequently achieve speech privacy. However, the research to date has focused on evaluating speech privacy when the masking noise is emitted from the normal loud speaker system all over the room. The masking noise emitted to the area where high level of speech privacy is not required, may cause an increased psychological impression of annoyance, leading to a decline in performance. In this study, we used a highly directional sound from modulated ultrasound as a masking noise for achieving speech privacy in the narrow area. Psychological experiments were conducted in which the masking sound was transmitted to participants from frontal directions with a parametric acoustic array speaker. Using the experimental data, the relationships between the degree of speech privacy and frequency characteristics that directivity of parametric acoustic array speaker were investigated. The results suggested that it is possible to maintain speech privacy in the narrow area by presenting highly directional masking sound.