This is a facility we toured yesterday at Hill:
http://www.okland.com/markets/federal/hill-air-force-base-f22-radar-cross-section-test-facility/
Inside, an F-22 or F-35 fighter can be balanced on two pylons, lifted into the center of the main chamber, and a turntable the pylons are mounted on rotates slowly, while the jet is hit with radar waves to ensure no "missed spots" in the radar-absorptive coating/paint (it doesn't take much of a missed area to ruin the whole cloak).
The chamber is huge (the stairs from the floor to the ceiling are 5 stories, as is the downstairs to the turntable supports) and some surfaces have radar absorbing cones (look just like anechoic cones, but absorb radar instead of sound) while the other surfaces are glass-smooth and I can't tell you what they're coated with, or the cones for that matter (classified).
But, I wanted to post about it because it was the most unusual-sounding room I've ever been in. When a sound, say a handclap, is first created you hear the sound directly. Then, immediately after you hear a single, distinct reflection, from the closest reflective surface (say, a nearby wall). Then you hear the first reflection from the next-closest wall, then the next, and soon you start hearing second reflections of the first reflections, and soon it all blends into a smooth, decaying sound known as reverberation. This is easy to experience inside any larger, reflective room, such as an empty gymnasium or church sanctuary. I have several rack-mounted "effects" units that can electronically simulate both the first reflection (called "slap-back") and the reverberation; my newest effects box, a Yamaha SPX-900 (admittedly many years old now) even featured parameters where you could enter the dimensions of the room, bare or carpeted floors, ceiling material, even drapes and wainscotting, feed it a dry signal and the output sounded just like it happened in that particular room. Great fun!
Anyway, back to the RCS facility. Because some surfaces were highly reflective, and others mostly absorptive, it gave the room a totally unique sound; I heard it right away as we walked in and my boss was talking. I clapped my hands once, and it sounded REALLY bizarre! It sounded like multiple slap-backs, but the sound never really got a chance to "blend" into reverberation, the distinct claps just faded away, quite slowly.
Dang, I wish you guys could hear it, I've experienced nothing like it before. Would also be interested to hear what a basketball game would sound like in there, would probably drive you insane. :geek:
http://www.okland.com/markets/federal/hill-air-force-base-f22-radar-cross-section-test-facility/
Inside, an F-22 or F-35 fighter can be balanced on two pylons, lifted into the center of the main chamber, and a turntable the pylons are mounted on rotates slowly, while the jet is hit with radar waves to ensure no "missed spots" in the radar-absorptive coating/paint (it doesn't take much of a missed area to ruin the whole cloak).
The chamber is huge (the stairs from the floor to the ceiling are 5 stories, as is the downstairs to the turntable supports) and some surfaces have radar absorbing cones (look just like anechoic cones, but absorb radar instead of sound) while the other surfaces are glass-smooth and I can't tell you what they're coated with, or the cones for that matter (classified).
But, I wanted to post about it because it was the most unusual-sounding room I've ever been in. When a sound, say a handclap, is first created you hear the sound directly. Then, immediately after you hear a single, distinct reflection, from the closest reflective surface (say, a nearby wall). Then you hear the first reflection from the next-closest wall, then the next, and soon you start hearing second reflections of the first reflections, and soon it all blends into a smooth, decaying sound known as reverberation. This is easy to experience inside any larger, reflective room, such as an empty gymnasium or church sanctuary. I have several rack-mounted "effects" units that can electronically simulate both the first reflection (called "slap-back") and the reverberation; my newest effects box, a Yamaha SPX-900 (admittedly many years old now) even featured parameters where you could enter the dimensions of the room, bare or carpeted floors, ceiling material, even drapes and wainscotting, feed it a dry signal and the output sounded just like it happened in that particular room. Great fun!
Anyway, back to the RCS facility. Because some surfaces were highly reflective, and others mostly absorptive, it gave the room a totally unique sound; I heard it right away as we walked in and my boss was talking. I clapped my hands once, and it sounded REALLY bizarre! It sounded like multiple slap-backs, but the sound never really got a chance to "blend" into reverberation, the distinct claps just faded away, quite slowly.
Dang, I wish you guys could hear it, I've experienced nothing like it before. Would also be interested to hear what a basketball game would sound like in there, would probably drive you insane. :geek:
