Active noise control at the openings of a compact acoustic enclosure

摘要

Passive acoustic enclosures are widely used to address industrial noise problematics where small to medium sized machines are involved. In most cases, the enclosure cannot be perfectly sealed and some openings have to be provided for adequate heat transfer. These openings may then be responsible for a significant drop in the performance of the acoustic enclosure. Classical approach to solve this issue consists in inserting mufflers at air inlets and outlets. However, absorbing materials used in these mufflers are performing well in the medium and high frequencies but lack the ability to reduce noise in low frequency. Active noise control approaches have been investigated to reduce the noise that leaks out through the openings of an acoustic enclosure. By using small control units with miniature loudspeakers and microphones placed near the openings, it is shown that overall performances can be improved, especially in the low frequency range. Particular attention has been paid to integrate industrial aspects early in the design, such as cost, weight and footprint. The proposed approach has been evaluated through several industrial applications, for which the use of conventional passive mufflers would not have been possible due to the constraints of weight and available space.