posted on Jan, 30 2013 @ 10:00 AM
It doesn't matter whether the surrounding area is populated or not. Hush houses are common at many Air Force bases. In 2008, the estimated number of
installations that have hush houses at Air Force, Air National Guard, Air Reserves, Navy, Marine Corps, and Army bases exceeded 100. There is one at
Edwards even though it is in the middle of nowhere, but security is as much of an issue as noise abatement. According to one DoD report, "The
structure allows continuous maintenance on all manner of military aircraft that could only previously be conducted outside or in open hangars,
potentially disturbing surrounding communities, and occurring in sight of prying eyes."
The air intake and exhaust systems of indoor engine test cells and hush houses are designed to optimize the engine air flows, and to discharge cooled
jet exhaust through a vertical stack. Supposedly, the intake and exhaust systems have silencers to reduce noise transmitted to the surrounding outdoor
area, but I have to say that it doesn't seem to keep the noise down all that much. Military aircraft produce high-decibel sound, particularly in the
afterburning mode. For example, a F-4 Phantom creates a noise level of 123.5 decibels adjusted (dBA) at 250 feet at regular military power and 130.6
dBA in afterburner mode. An F-16 creates a noise level of 122.0 dBA in military power mode and 129.3 dBA in afterburner mode. During an engine run in
a hush house, people in the nearby surrounding area feel a bone-rattling, deep, low hum. I find it exceedingly unpleasant.
There are two basic types of aircraft acoustical enclosures: the hush house, and the test cell. Hush houses are hangar-like structures designed for
testing air-driven jet engines, including turbojet, turbofan, turboprop, and turboshaft engines. A jet engine test cell is usually an indoor engine
testing facility designed only for out-of-frame testing of aircraft engines. These test cells are constructed from concrete, have an intake stack,
test enclosure, a blast augmenter, and an exhaust ramp and/or stack. There are two engine test cells at the southernmost end of the Area 51 complex
that were originally built to support the OXCART program. Judging from recent satellite images, they appear to remain available for use. The hush
house on the north end can accommodate aircraft with the engines installed, allowing four integrated testing. Engine maintenance has always been a
challenge for the Red Hats programs at Area 51 due to the paucity of spare parts for the foreign aircraft, and engine performance testing is an
important part of any aircraft evaluation program.