LORD HAS flight-tested active noise- and vibration-control on a McDonnell Douglas DC-9 and expects US supplemental type-certification of the system in November. The company says that its NVX Active System for the DC-9 and MD-80 series eliminates engine tones and reduces cabin noise by "as much as 70%".
The system monitors cabin noise and drives actuators mounted on the engine pylons to eliminate vibration. The NVX controller combines engine-speed signals with data from 16 microphones behind the trim panels in the aft cabin, and sends commands to six actuators in each engine pylon.
The actuators replace tuned vibration-absorbers and generate forces to counteract disturbances coming from the engine. Lord is demonstrating the system to potential customers at its Cary, North Carolina, development centre, using a full-scale mock-up consisting of a DC-9 aft-fuselage section, complete with interior.
Programme manager Becky Weih says that flight tests "- have demonstrated effective elimination of engine tones over a range of flight conditions. With the system, the aft [seat] rows of the DC-9 became as quiet as the front rows."
Erie, Pennsylvania-based Lord says that its NVX Active System is retrofittable to a DC-9 or MD-80. The location of the microphones is not critical, the company says, and they can be integrated with overhead passenger-service units and installed without removing the cabin trim.
Source: Flight International
