Cocktails, but no party: multipath-enabled private audio
This addresses privacy in audio communication for specific users in shared spaces, though it appears incremental as it builds on personal audio zone concepts.
The authors tackled the problem of private audio messaging by using echoes to unscramble messages only at predetermined locations, achieving unintelligible sound elsewhere with a modest number of loudspeakers and minimal measurements.
We describe a private audio messaging system that uses echoes to unscramble messages at a few predetermined locations in a room. The system works by splitting the audio into short chunks and emitting them from different loudspeakers. The chunks are filtered so that as they echo around the room, they sum to noise everywhere except at a few chosen focusing spots where they exactly reproduce the intended messages. Unlike in the case of standard personal audio zones, the proposed method renders sound outside the focusing spots unintelligible. Our method essentially depends on echoes: the room acts as a mixing system such that at given points we get the desired output. Finally, we only require a modest number of loudspeakers and only a few impulse response measurements at points where the messages should be delivered. We demonstrate the effectiveness of the proposed method via objective quantitative metrics as well as informal listening experiments in a real room.