MEASUREMENT OF ACTIVE CONTROL EFFICIENCY AROUND NOISE BARRIERS

This paper presents results of measurements of active noise control ef ficiency around noise barriers in an outdoor experiment around a real wall. The study is here limited to stationary noise, either harmonic o r pink noise, created by a loudspeaker and controlled with the help of loudspeakers as secondary sources. The aim is to reduce the sound pre ssure in the shadow zone where error microphones are placed. The purpo se of the experiment is mainly to find the space and frequency, domain s over which the control is efficient and to give an estimate of the s upplementary attenuation provided by the actively controlled noise bar rier over a classical one. The second purpose is to estimate the influ ence of the secondary source and error microphone positions and the in fluence of the number of sources and microphones used on the performan ces of the system. In each case comparisons are made with values calcu lated by a boundary integral equation software in order to validate th is tool and then to be able to simulate the system efficiency from the knowledge of its different parameters. (C) 1998 Elsevier Science Ltd. All rights reserved.