Sealed, close-fitting, machine-mounted acoustic enclosures with predictable performance

Sealed, close-fitting, machine-mounted, acoustic enclosures are often the most appropriate method for reducing the levels of machine-generated noise to which people are exposed. Machine noise is often associated with vibration of the machine surfaces; thus the surfaces of close-fitting, machine-mounted, acoustic enclosures are often forced to vibrate and radiate sound as a result of both the acoustical and the mechanical coupling between the machine and the enclosure. A form of construction which gives good and predictable acoustic performance, as defined by insertion loss, is described along with the prediction procedure. The effectiveness of the prediction procedure is illustrated by comparing the redicted and measured one-third octave band insertion losses for a representative enclosure. Measurements which show the effects of altering some important enclosure parameters are also given.