A Flexible Acoustic Sensor Network for Various Monitoring Applications

Acoustic monitoring using a sensor network is a powerful instrument to assess and manage complex noise situations. It can provide a basis to identify appropriate and cost effective measures, and to assess their effect by comparing before and after implementation. It can also be an instrument for communication and policy making. However, the requirements for various monitoring applications can differ significantly, which asks for a flexible approach for an acoustic sensor network. A monitoring approach has been developed which is based on two types of low cost acoustic sensor nodes, a basic wireless sensor node and an advanced sensor node in a scalable architecture. The basic node only measures sound levels, while the advanced node measures time signals and is programmable to compute various signal properties such as the spectral content and peak level. Both sensor types can be freely combined in an acoustic sensor network. This network is very flexible and can cope with the various applications of acoustic monitoring. Three different situations where the acoustic sensor network approach was applied will be discussed. The first one deals with investigation of the noise sources around canals in a major Dutch city. The second deals with noise emission of trams on a steel bridge to understand the noise source mechanism and to take appropriate measures to reduce the noise. The third deals with detection and localization of annoying events in an urban environment. The goals for the three applications were completely different, but the same network could be easily adapted to obtain the required information. Monitoring results of the three applications will be discussed together with the performance of the acoustic network.