After reading the Wyvern thread about how loud the Scimitar was, what's the
loudest jet you've ever heard? Mine is an SR-71 at Edwards just before they
went out of service. That shook the fillings in my teeth. Anybody ever see
an XB-70 takeoff? That seems like a major noise pollution source.
A Harrier may not be the "loudest", but is has a screaching, high
pitched whine at idle that would blow out a dog's eardrums, let alone
remind you of a trip to the dentist. Especially if you're standing
directly in front of the inlets.
The last time we went to Miramar, to soothe SWMBO we bought chalet tickets
at show center. They handed out free earplugs- with a Harrier hovering about
100 yards in front of us, they were extremely necessary.
The high frequency noise is apparently due to the metal from which the
compressor bearings are made. The bearings on a F-16 are made from a similar
material, and it presents a similar high frequency hazard. The difference
with a Harrier is that the bearings for the first-stage compressor are
literally within arms reach of the intake lip!
During the late-1980s groundcrew on the RAF Harrier force were issued with
slimline ear defenders. These were designed to sit underneath the kevlar
helmet so that linies could wear full combat gear while deployed in the
field. It was only after eighteen months that it became apparent that the
ear defenders were designed to protect infantrymen against the noise of
gunfire... not against high frequency aircraft noise! Those of us who spent
any appreciable time on Harrier lines in those days all suffer from a
certain amount of high-tone deafness. Pardon?
Yeah, having watched a B-58 take off with FOUR afterburners blazing in a
rainstorm at Bunker Hill (now Grissom) AFB in 1967 I gotta concur.
I recall seeing an F-105 undershoot the runway while in Basic Training at Fort
Dix (it was next to the main runway at McGuire AFB) and when he hit the burner
to schooch it to the touchdown strip it got very, very loud. He also toasted
about a dozen ducks in a pond off the end of the runway...
Actually heard with my own ears. It's either a pair of F-15s hitting the
afterburners on a flyover at the race track or a pair of F-4s staging out of
Pope AFB many moons ago when I was a kid. Things always seem bigger and
louder when you're a kid, so I'll go with the Phantoms. ;-)
And firstname.lastname@example.org (AMPSOne) opened up and revealed to the world
Let me guess, there was "roasted" duck on the menu in the mess hall that
night. . .;-)
I think that's an inherant property of jet engines in general, but I'll
agree that the inlet definatly has something to do with it. F/A-18s
have a similar highly directional high frequency content comming out of
the inlets, but an E/F has a different pitch/sound than an A-D. I
figure it's ont only the engine but also the acoustic noise from the air
volume mixing with the engine noise and cavity effects in the duct.
When I was designing compressor components for GE I ran across more than
one instance where acoustic coupling had structural effects on engine
components. In one case I recall having to change the number of
bearings in a #1 race to get around a problem.
I was having an early lunch in a Roy Rogers in down town Frederick
Maryland when an F-117 went over very low. It was the weekend of the
Frederick airshow. There wasn't anybody sleeping late in Frederick after
I've only seen an F-117 up close once,at an airshow.Wasn't anything like as
loud as the F-15 and F-16s I saw at the same show.
I'd say a B-1 in afterburner was the loudest I'd seen,but the F-15 came close.
Probably none of us here ever heard it, but the XF-84H 'Thunderscreech'
was reputed to put out such a high-pitched din that it caused
debilitating nausea on the surrounding air base apron. However, that
might not have been strictly jet noise, since it was caused by the tips
of the propeller going supersonic.
I've had a Magister or 2 at my airport & they aren't all that loud.
I've never heard an F-117 that I'm aware of, but I've read that it's
not much louder than a Cessna Citation. I always took that to mean like
a Citation I or II since they were around when the F-117 came out. I
hear Citations all the time, & rarely need hearing protectors on the
ground, much less in flight.
Concorde in full reheat on takeoff for a transatlantic flight. It was
loud *inside* a 737 taxying past. It was also dusk so the sight of the
reheat plumes trailing behind is forever engraved in my memory.