A Control Source Structure of Single Loudspeaker and Rear Sound Interference for Inexpensive Active Noise Control

Yasuhide Kobayashi,Naoki Jinbo,Hisaya Fujioka

doi:10.1155/2010/730813

Abstract

Active noise control systems of simple ducts are investigated. In particular, open‐loop characteristics and closed‐loop performances corresponding to various structures of control sources are compared based on both mathematical models and experimental results. In addition to the standard single loudspeaker and the Swinbanks′ source, we propose and examine a single loudspeaker with a rear sound interference as a novel structure of control source, where the rear sound radiated from the loudspeaker is interfered with the front sound in order to reduce the net upstream sound directly radiated from the control source. The comparisons of the control structures are performed as follows. First, the open‐loop transfer function is derived based on the standard wave equation, where a generalized control structure unifying the three structures mentioned above is considered. Secondly, by a comparison of the open‐loop transfer functions from the first principle modeling and frequency response experiments, it is shown that a certain phase‐lag is imposed by the Swinbanks′ source and the rear sound interference. Thirdly, effects on control performances of control source structures are examined by control experiments with robust controllers.

Highlights

It is well known that the Swinbanks’ source [1] has advantages against a standard single loudspeaker in performances and the implementation cost
We propose a new structure of control source which is composed of a single loudspeaker with a rear sound interference so that the rear sound radiated from the loudspeaker is interfered with the front sound in order to reduce the net upstream sound directly radiated from the control source
The validity of the proposed method will be shown by comparing to the existing two structures of control sources, namely, the standard single loudspeaker and the Swinbanks’ source, in terms of the open-loop characteristic and the closedloop performances based on both mathematical models and experimental results

Summary

Introduction

It is well known that the Swinbanks’ (unidirectional) source [1] has advantages against a standard single loudspeaker (bidirectional source) in performances and the implementation cost. One can expect that a single loudspeaker can achieve a similar performance to the Swinbanks’ source if the rear sound could be interfered to reduce the front sound at an upstream junction through some additional ducts. The validity of the proposed method will be shown by comparing to the existing two structures of control sources, namely, the standard single loudspeaker (bidirectional source) and the Swinbanks’ (unidirectional) source, in terms of the open-loop characteristic and the closedloop performances based on both mathematical models and experimental results

Experimental Apparatus

First Principle Model

Comparison of First Principle Model and Experimental Results

Controller Design and Control Experiments

Experiments Gyu

Conclusions