Investigation of electric network frequency for synchronization of low cost and wireless sound cards

An electric network frequency (ENF) signal can be found in multimedia recordings due to propagation from the power grid. There a variety of applications based on ENF signal use, such as video and audio stream synchronization, and origin determination of multimedia recordings. In this paper, we propose the use of ENF to synchronize real-time audio streams from different, non-synchronized sound devices, for instance from wireless sound cards or low cost USB sound cards. Synchronization of separate audio streams can be achieved by aligning their embedded ENF signals. Our goal is to find out how accurate a synchronization using ENF at different SNR levels can be. We show simulation and real-time experimental results of audio stream synchronization. We found that with sufficient ENF level we can achieve an accuracy of the estimated delay difference of four samples at 44.1 kHz sampling rate.