Patent ID: 6419576
Filing Date: 2002-07-16
Classification: F04D,F24F,Y10S

Abstract:
An air duct silencing apparatus for use as an inlet silencing duct to be connected to an air supply fan unit for a building or other large structure, said apparatus comprising:an exterior housing having exterior walls forming outer surfaces of said housing, an air inlet formed on one end of said housing, and a circular air outlet formed in an opposite end of said housing and adapted for connection to the fan unit for airflow to the fan unit, said outlet defining a primary central axis extending through the center of said outlet and perpendicular to a plane in which the outlet lies; interior walls arranged in said housing, connected to said exterior walls and defining an annular airflow passageway extending from said air inlet to said air outlet, a substantial portion of said interior walls being made of perforated metal; a central airflow defining member located in and further defining said annular airflow passageway and having a second central axis extending from an outer end thereof to an inner end adjacent said air outlet, said second central axis being substantially coaxial with said primary central axis, said airflow defining member being substantially circular in transverse cross-section along its length and having a relatively wide bulbiform end section at said outer end thereof and a relatively narrow end section at said inner end, and sound absorbing material in said housing and covered by said interior walls and also in said airflow defining member, wherein said airflow passageway tapers inwardly in the direction of said air outlet and the cross-sectional flow area of said annular airflow passageway varies along at least a substantial portion of its length so that airflow speed at said air inlet is low relative to airflow speed at said air outlet when said air duct silencing apparatus is connected to said fan unit and the fan unit is operating.