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Adaptive Audio Synchronization Scheme Based on Feedback Loop with Local Clock in Wireless Audio Sensor Networks

Wireless Audio Sensor Networks (WASNs) can provide event detection, object tracking and emergency response through cooperative audio sensor nodes. Effective collaboration of audio sensors requires precise synchronization among audio streams. Some researches have been done on the timestamp mechanism based on time synchronization ignoring propagation delay and many other researches have focused on the synchronization of simple gunshot or scream. However, for the synchronization of intermittent and fluctuating audio stream, there still exists many challenges. In this paper, we propose an effective audio synchronization scheme which can synchronize the intermittent audio streams adaptively while maintain low energy cost. On one hand, we obtain audio synchronization without global clock which save energy tremendously. On the other hand, by introducing a feedback loop mechanism, we can keep a high audio synchronization fidelity even when the audio source moves around and the sound strength varies with time. Furthermore, we discuss the extension for flexibility and scalability of this scheme when there exist several sound sources simultaneously or the audio source moves among clusters. Through experiments on a WASNs platform and simulations, we show that the proposed scheme is desirable to guarantee the accuracy of audio synchronization in practical environment with low energy cost.