Active noise control of enclosed centrifugal blowers

Global active noise control has been obtained on the tonal noise from a small centrifugal blower, similar to those used in laptop computers. Compact control systems were investigated for two configurations. The blower was mounted in both a short rectangular duct and in a mock laptop case that was modeled as a two-dimensional rectangular enclosure. Secondary sources and error sensors were located adjacent to the duct or inside the enclosure. Error sensor locations were guided by analytical models for minimization of power radiation from ducted or enclosed simple sources. This paper demonstrates the experimental verification of both of these models, which shows significant global sound power reduction of the blower's primary tone in both cases.