Abstract: An Active Muffler in the form of a duct having two open ends for conveying air from a within a cabinet to outside the cabinet. A fan or blower is incorporated in the duct. An Automatic Noise Control (ANC) unit is associated with the duct, and at least one microphone and at least one speaker are incorporated in to the duct for noise-reduction. An outer portion of the duct may be sound-absorbing material. the ANC unit may cause noise to be shifted to a frequency that can be absorbed by the sound-absorbing material.

Abstract: An Active Muffler in the form of a duct having two open ends for conveying air from a within a cabinet to outside the cabinet. A fan or blower is incorporated in the duct. An Automatic Noise Control (ANC) unit is associated with the duct, and at least one microphone and at least one speaker are incorporated in to the duct for noise-reduction. An outer portion of the duct may be sound-absorbing material. the ANC unit may cause noise to be shifted to a frequency that can be absorbed by the sound-absorbing material.

Abstract: Soundproofing a rack by installing at least one duct on at least one panel of the rack, or as part of the side panels of the rack, or is mounted inside the rack as a drawer in such a way that air can flow outside from the rack causing air to flow from the rack through the duct, and providing an active noise control (ANC) system within the duct. Passive noise control may also be provided in the duct. At least one fan may be provided at an inlet of the duct Fan speed may be controlled, in response to a climactic condition within the rack. The duct may comprise a back panel which is added on or a replacement for an existing back panel of the rack. A muffled inlet may be provided on another external surface of the rack.