Noise attenuator

Claim 1

The combination, with a hood positioned adjacent a food preparation area within a building and an air pollution control system including an afterburner disposed outside the building and in which particulate grease is burned and noise is generated and a duct extending between the hood and the afterburner and through which airborne particulate grease is conveyed from the food preparation area, the duct including a vertically rising portion and a horizontally directed portion forming an ell with the vertically rising portion, of an arrangement for attenuating noise otherwise transmitted from the afterburner to the hood and comprising first and second noise attenuating devices each comprising a grease impervious film bag, energy absorbing means sealed within said bag for dissipating by mechanically compressive absorption sonic energy impinging on said bag, said bag precluding accretion of grease on said energy absorbing means and thereby avoiding decay in the noise attenuation efficiency thereof, and means for mounting said bag within said duct in exposure to sonic energy being transmitted from the afterburner to the hood, said mounting means disposing said first noise attenuation device adjacent said ell for substantially direct, perpendicular impingement of sonic energy thereon and mounting said second noise attenuator device in predetermined spaced relation within the duct from said first noise attenuator device.