Distributed Microphone Arrays for Digital Home and Office

With the proliferation of pervasive computing in digital home and office environment there is an increasing demand for hands-free audio and video interfaces. Microphone arrays are already present on desktops and mobile computers, and camera arrays are in transition from being highly sophisticated prototypes to become affordable consumer devices soon. Thanks to increasing CPU power of general-purpose computers and higher bandwidth in wired and wireless networks, it now becomes possible to perform array signal processing of audio using networked sensors, actuators and computers. This paper presents components of a prototype system developed to support hands-free audio capture for audio recording and voice recognition based on multiple wirelessly networked laptops with onboard microphone arrays. Several key technologies demonstrated in this system include: 1) time synchronization scheme for distributed audio input devices that uses wireless network; 2) localization algorithms to reconstruct the geometry of audio sensors and speakers in a room; 3) cascaded beamforming algorithms for signals captured by distributed microphone arrays. This paper discusses both theoretical and practical aspects of mapping array signal processing algorithms on a distributed network of general-purpose computers with integrated audio sensors. Our experimental results demonstrate great potential of distributed audio arrays for hands-free command-and-control when compared to an array located on a single platform