Cocktails, but no party: multipath-enabled private audio

TL;DR

This paper introduces a private audio system that uses room echoes and multiple loudspeakers to deliver clear messages at specific locations while keeping sound unintelligible elsewhere, enhancing privacy in shared spaces.

Contribution

It presents a novel echo-based multipath audio delivery method that requires minimal measurements and equipment, enabling private messaging in a room environment.

Findings

Effective at focusing audio messages at designated spots

Sound is unintelligible outside focusing locations

Achieves privacy with few loudspeakers and measurements

Abstract

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.