Feesback-type active control of noise inside waveguide

Abstract

In the modern society, development of noise abatement technologies for machines and structures have become an important issue to realize a comfortable sound environment for humans. The growing interest for noise problems may be due to the increase in large-scale industrial machinery such as engines, fans, blowers, transformers, and compressors. For these noises, it is necessary to choose different measures according to the characteristics of the noise generation mechanism. Noise prevention measures can be divided into two categories: passive noise control (PNC) and active noise control (ANC). Sound absorbing materials are commonly used for PNC. Although the materials can be adopted for noise environment in a wide frequency range, the sound reduction is not efficient specifically for a low-frequency noise. Therefore, ANC, in which secondary sound source is used to mute the target noise, is expected to be an effective means. In this study, we constructed a feedback type ANC system and evaluated the noise reduction performance by numerical simulation and experiment for controlling one-dimensional noise in a duct. The proposed system worked effectively for reducing the noise in the duct with a simple device configuration, however, the performance leveled off due to the amplification of the untargeted noise component. The part will be our future task.