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We propose a power management method using a digital voice activity detection (VAD) module for intelligent ubiquitous sensor systems. When this VAD module detects a speech signal, a main signal processing circuit is connected to a power source. When no speech signal is detected, most circuits except VAD are blocked off, thereby reducing stand-by power for the specialized sensor nodes used for speech signal processing. We implemented the VAD algorithm, using zero crossing of input signals to an FPGA, thereby achieving 2.10 mW operation. We synthesized this VAD module using CMOS 0.18-μm process, achieving 3.49 μW power consumption for operation at 1.8 V and 100 kHz.

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Abstract-We propose a microphone array network that realizes ubiquitous sound acquisition. Nodes with 16 microphones are connected to form a large sound acquisition system that carries out voice activity detection (VAD), sound source localization and sound source separation. The three operations are distributed among nodes using network. Because the VAD is implemented to manage power consumption, the system consumes little power when speech is not active. The power of the VAD module is only 2.1 mW on an FPGA. The system can improve an SNR by 7.75 dB using 112 microphones.Index Terms-Microphone array, ubiquitous sensing, sensor network, distribution network, low-power system ISCAS Track Selection-Digital Signal Processing INTRODUCTIONIn recent years, information processing technology improvements have realized real-time sound processing systems with microphone arrays. A microphone array can localize sound sources and separate multiple sources using the acquired sounds' spatial information. The computational effort of these operations increases polynomially with the number of microphones, but the performance of these operations is known to improve concomitantly [1]. To reduce the increasing power of a microphone array and to satisfy the recent demand for ubiquitous sound acquisition, it is necessary to realize a low-power, large sound-processing system.Huge microphone arrays have been widely researched at Tokyo University of Science (128 ch To implement a microphone array as an actual ubiquitous sound acquisition system, we propose to divide the huge array into sub-arrays and produce a network: an intelligent ubiquitous sensor network (IUSN). The sub-array nodes can be set up on a room's walls and ceiling. The performance can be improved by increasing the nodes, but the communication between nodes does not increase so much in our system.