US Patent 11378305 Noise reducing air duct

An air duct includes a first chamber and a second chamber, the first chamber being defined between an air handling device and the second chamber, and the second chamber being defined between the first chamber and an environment exterior to the air duct, a plurality of first openings between the first chamber and the second chamber, a plurality of second openings between the second chamber and the environment exterior to the air duct, and a sound absorbing material defining at least a portion of an interior surface of at least one of the first chamber and the second chamber.