ACTIVELY CONTROLLED HOOD FOR MACHINERY NOISE

THE PROPOSED PROJECT WILL DEVELOP A CONCEPT FOR A MACHINERY HOOD DESIGNED SPECIFICALLY TO REDUCE NOISE USING ACTIVE CONTROL TECHNIQUES. THE STRUCTURAL DESIGN, A STIFF "MEMBRANE", FACILITATES THE USE OF ACTIVE CONTROL BASED ON MINIMIZING THE VIBRATIONAL RESPONSE OF THE ENCLOSURE SURFACE. THE POTENTIAL ADVANTAGE OF ACTIVE CONTROL RELATIVETO PASSIVE APPROACHES IS INCREASED PERFORMANCE AT STRUCTURALRESONANCES AND AT LOW FREQUENCY WHERE RIGID-BODY MOTIONS AREIMPORTANT. COMPATIBILITY OF ACTIVE CONTROL WITH LIGHTWEIGHTSTIFF STRUCTURES SUGGESTS THAT THIS APPROACH MAY HAVE MORE WIDESPREAD APPLICATION TO NOISE AND VIBRATION CONTROL IN OTHER EFFICIENT STRUCTURES. SPECIFIC OBJECTIVES OF THE STUDY ARE THE FOLLOWING: (1) EVALUATE THE ABILITY TO OBTAIN A STRUCTURAL RESPONSE FIELD DOMINATED BY LONG WAVELENGTHS; (2) EVALUATE THE PERFORMANCE OF SUCH A STRUCTURE IN STRATEGIES FOR ACTIVE CANCELLATION; (3) EVALUATE DESIGN CONCEPTS FOR ACHIEVING REQUIRED STRUCTURAL CHARACTERISTICS.