Airport Lab

The Vibration and Acoustics Laboratory at the Virginia Tech Airport is run in cooperation with the Gas Turbine Laboratory (W.F. O'Brien , Director). This lab is located about 2 miles from the campus and houses an operational Pratt and Whitney JT15D-1 turbofan engine. The diameter at the fan stage location is 0.53 m, and the engine can generate up to 2500 lbf of thrust. The engine is mounted in a test stand, in a cell, equipped with a semi-anechoic chamber on the engine inlet side and a small-scale hush-house augmenter tube and deflector plate assembly on the exhaust side. The test facility provides the opportunity to develop and implement noise control techniques on an actual operating jet engine. The inlet radiated noise primarily tonal in nature at mid to high frequencies (from about 2000 to 4000 Hz) while the exhaust noise is essentially broadband with the most significant content existing in the low frequency range (from 10 to 200 Hz). Research involving both passive and active noise control methods is being conducted to develop systems to reduce the radiated noise from both the inlet and the exhaust of the jet engine. Active control using low profile, high power acoustic sources mounted in the engine inlet has resulted in total inlet radiated acoustic power reductions of over 5 dB. Active noise control methods have resulted in exhaust noise reductions of over 14 dB in some one-third octave bands below 200 Hz. The test cell has also been modified to represent a small scale hush house with a near exhaust tube and deflector plate. Active control studies have been performed on reducing hush house radiated noise. Other jet engines are available for test including a F109 on a movable test stand.

Another area is used to test a 2.8m long 2.5m diameter composite cylinder manufactured by Boeing in which sits a 7ft. long 6ft. diameter aluminum cylinder. Testing being done on this cylinder is for control of sound transmission into a rocket payload compartment.