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3.8 Rotorcraft Noise ReductionNASA researchers have succeeded in demonstrating aircraft cabin noise reduction using a hybrid noise control technology that leverages active noise control with a detailed knowledge of structural dynamics. Termed Active Structural Acoustic Control (ASAC), the technology improves noise controller performance by attacking aircraft interior noise closer to its source: fuselage structural vibrations. In addition, ASAC control technology reduces noise levels without the weight penalty that is associated with conventional, passive noise reduction methods. Research data obtained so far has indicated that ASAC controllers can deliver competitive noise reduction even though they use less power and fewer control channels than classic active noise controllers. This translates to lower cost noise control systems for our aerospace industries.
Piezoceramic actuators provide the driving force to control sound radiating from an aircraft fuselage panel during a supersonic wind tunnel test. This is the first-ever demonstration of active control for interior cabin noise induced by supersonic turbulent boundary layer flow. The capability of the ASAC technology was demonstrated in two experiments. First, a wind tunnel test demonstrated ASAC control of sound generated by the random action of subsonic and supersonic turbulent flow on an aircraft sidewall. Second, in a flight test using a Beech 1900D turboprop aircraft, an optimized array of structural actuators reduced cabin noise from the propeller by more than half. These technologies will enable the use of more effective and efficient structural designs for a range of aerospace vehicles.
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NASA Headquarters Responsible Official: Code R
Curator: SAIC Information Services http://www.aerospace.nasa.gov |
