Absorptive sound attenuator, in particular for air ducts in paper mills

A sound attenuator for use in connection with air ducts, in particular for intake and/or exhaust air ducts of paper mills, comprising an enclosure having an outer wall and an aperture formed thereto;

• a conduit forming an air duct for transmitting an air flow, having a perforated wall, located inside said enclosure, said perforated wall allowing acoustic vibrations from the conduit to be transmitted therethrough;
• removable sound absorbing material for absorbing acoustic vibrations in the area around said conduit which are transmitted through the perforated wall, located inside said enclosure and around said conduit;
• and means for opening and closing said aperture for selectively inserting and removing said sound absorbing material, through said aperture, from outside of said conduit, wherein said enclosure further comprises a longitudinal axis, said conduit is disposed in a plane parallel to the longitudinal axis, so that air flows generally parallel to said longitudinal axis of the enclosure, further comprising guides and at least one plate of absorption material disposed inside said conduit, said plate comprising layers of absorption material sandwiched between two perforated plate walls, said walls lying in a plane generally parallel to said longitudinal axis and wherein said absorption plate is generally planar and slidably arranged in the guides, so that said absorption plate can be removed for cleaning or replacement and inserted through said aperture of said enclosure.

A sound attenuator for use in connection with air ducts, in particular for intake and/or exhaust air ducts of paper mills, comprising an enclosure having an outer wall and an aperture formed thereto;

• a conduit forming an air duct for transmitting an air flow, having a perforated wall, located inside said enclosure, said perforated wall allowing acoustic vibrations from the conduit to be transmitted therethrough;
• removable sound absorbing material for absorbing acoustic vibrations in the area around said conduit which are transmitted through the perforated wall, located inside said enclosure and around said conduit;
• and means for opening and closing said aperture for selectively inserting and removing said sound absorbing material, through said aperture, from outside of said conduit, wherein said enclosure further comprises a longitudinal axis, said conduit is disposed in a plane parallel to the longitudinal axis, so that air flows generally parallel to said longitudinal axis of the enclosure, further comprising at least one membrane plate which is capable of oscillating in response to ambient acoustical vibrations, disposed inside said conduit and lying in a plane generally parallel to said longitudinal axis, so that the acoustical vibrations are decreased in amplitude, and wherein said membrane plate is generally planar and slidably arranged in guides, so that said membrane plate can be removed for cleaning or replacement and inserted through said aperture of said enclosure.