Development of a compact device for duct noises

Abstract

Noise radiated from ducts associated with air conditioning equipment is one of the most important noises that must be addressed to create a quiet space. While it is relatively easy to reduce this noise if the equipment works at a constant frequency, it is difficult to reduce noises of various frequencies being generated depending on changes in its output. Although a side branch is one of the solutions for duct noises, a single side branch can only be effective for a specific frequency. On the other hand, multiple side branches can broaden the effect, However, the space required for side branches becomes very large and is not practical for use. In this study, a compact duct noise reduction device based on the side branch concept is proposed. The side branches of multiple lengths filled with porous materials are considered to achieve both a wide-band reduction and space saving. The design process of the device which can be installed easily is illustrated and the reduction performance are estimated by numerical studies.