Good Lord! It's Quiet Here

Flight tests of the Lord Corp. NVX Active Noise and Vibration Control system have demonstrated a decrease of as much as eight decibels in noise and vibration in the aft cabin of DC-9/MD-80 series aircraft and up to six dBs in the Raytheon King Air cabin.

The Lord system uses microphones or accelerometers to detect interior noise. For fuselage-mounted jet engines, pylon-mounted actuators are driven by a central controller and generate forces to counteract the noise and vibration of the engine. The propeller aircraft system uses audio speakers inside the cabin to deliver the counter frequencies.

This B/CA reporter noticed a significant reduction in the 160-Hertz growl of the engines at cruise when the system was activated during a demonstration flight aboard the Dallas Mavericks' DC-9-30 team aircraft from Addison Airport near Dallas recently. A six decibel level reduction was measured when the system was activated at our 33,000-foot cruise altitude - a decrease of six amounts to half the sound.

Lord has STCs for the DC-9/MD-80 and all series of King Airs. Systems for other business jet aircraft are under development. Cost is about $50,000 for the DC-9 series and about $35,000 for the King Air.

By Jim Street