Auditory masking control system for protecting speech privacy by playing back filtered BGM sounds with flat-panel loudspeakers

Conversation sounds spoken over prescription pharmacy counters between pharmacists and customers may include privacy information of the customers. This vocal privacy information can be easily leaked to the other customers waiting in the same pharmacy store. In order to protect the above speech privacy information, a method of generating white noises in a target room on purpose has been proposed. However, this method will give us uncomfortable environments and has been not widely used, especially in Japanese pharmacy stores. We propose a novel BGM system giving protecting functions for speech privacy information, by proposing a filtering method for generally used music or natural sound signals, in order to emphasize their auditory masking functions against speech sounds as strong as white noises. We have made three kinds of both objective and subjective evaluations for our proposed filtering processes. As one of the subjective evaluations, we installed our developed flat-panel loudspeaker in a waiting room of a large-scale prescription pharmacy store, and have tried our proposal there. As a result, we could not recognize any quality distortion in masker sounds played back, whereas we could find difficulty to listen to conversation sounds between couples of a pharmacist and a customer at the waiting area, as far as heard masker sounds had proper level.