A distributed array processing using multi-channel signals over a network with an embedded time code by the network time protocol

Abstract

A conventional microphone array system uses a conductor to wire from a microphone to an input via an amplifier. While, a wireless transmission for an array system makes the configuration flexible, and it is expected to provide novel applications widely, such as measuring of impulse response in wide area. One of the issues is a synchronization of time between channels. This paper proposes multiple signals transmission system over a network with a time code embedding to synchronize those signals. The system consists of clients and a server. Each client at a receiving point runs a network time protocol client daemon, and a packetized audio signal with a time code is sent to a server. The signal from a client is reconstructed at a server based on the time code. Since the time differences between clients affects to performance of the multichannel signal processing, small error in time at a client is preferred. This paper discusses how the error in time between channels affects to performance of the distributed microphone array system.