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What is that big rumbling noise we hear in east Victoria?


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#141 LJ

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Posted 22 November 2017 - 07:53 PM

At YYJ?

No. Luke AFB.


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#142 LJ

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Posted 22 November 2017 - 07:58 PM

They must have had the throttles very low. F15s have considerably more powerful and older engines.

No they are much quieter, very noticeable.

 

http://www.f-16.net/...pic.php?t=11267

 

http://www.airliners...c.php?t=1008373


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#143 Mattjvd

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Posted 22 November 2017 - 09:58 PM

No they are much quieter, very noticeable.

http://www.f-16.net/...pic.php?t=11267

http://www.airliners...c.php?t=1008373


I haven't heard an F-35 and it uses a brand new engine I know little about. I gave that Air Force Times link a read, so I'll say you're right, it's louder. But the F15 would be louder than an F18/F16 at equal percentages of throttle applied. At cruise over Victoria, I'm sure they were at >40%

#144 AllseeingEye

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Posted 22 November 2017 - 11:27 PM

They must have had the throttles very low. F15s have considerably more powerful and older engines.

I was going to say the same; the air frame design is now 45 years old back when they were cramming them with crazy powerful power-plants. Even the "enhanced" F-15 Strike Eagles are now well over 25 years old. Max performance on these old beasts is well in excess of 1700mph at altitude, which is far faster than any F-18 or (especially) F-16 can fly.



#145 LJ

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Posted 23 November 2017 - 08:06 PM

According to http://www-nehc.med.....Protection.ppt here is the sound levels of the following. 

EA-6B 148 dB
F-14 153 dB
F-16 150 dB
F-18F 150 dB
F-15C 149 dB
F-35 152 dB

So they all make about the same noise but the F-16/F-18 is louder than the F-15, but the F-14 and F-35 are both louder than everything else.

But I do agree that for a similar cruise speed the F15 would require less throttle input.


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#146 Mattjvd

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Posted 23 November 2017 - 08:24 PM

According to http://www-nehc.med.....Protection.ppt here is the sound levels of the following.

EA-6B 148 dB
F-14 153 dB
F-16 150 dB
F-18F 150 dB
F-15C 149 dB
F-35 152 dB

So they all make about the same noise but the F-16/F-18 is louder than the F-15, but the F-14 and F-35 are both louder than everything else.

But I do agree that for a similar cruise speed the F15 would require less throttle input.


That's really interesting LJ, I'm surprised.

I wonder what made the difference (in noise level) between the F15s and F18s. Considering the age and power difference.

#147 Bingo

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Posted 23 November 2017 - 09:22 PM

I wonder what made the difference (in noise level) between the F15s and F18s. Considering the age and power difference.

 

Noise seems to lessen with age as our hearing gets more selective. That's the difference.


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#148 AllseeingEye

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Posted 23 November 2017 - 09:44 PM

As loud as the F-18 is it pales compared to certain other fighters particularly in Europe. The grand-daddy of noise has to be the B1 Lancer bomber; I was at an airshow in WA state a few years ago - being exposed to a B-1 on afterburner is something you never ever forget. An F-18 is putting out around 32,000lbs of 'burner thrust, whereas the B-1 is pounding out an otherworldly 120,000 lbs of thrust; it went supersonic about half a mile from the crowd at about 500 feet. Holy hell....

 

Re: engine thrust and "noise", jet engine thrust is all about mass flow rate. Thrust is directly dependent on it.  How you choose to move that flow through your control medium (the engine) is based on your platform requirements. Trade-offs between thrust at sea level and altitude at various speeds, noise, and fuel consumption are all carefully considered when designing a high performance jet engine.
 
Let's say we are designing two very different engines with the same target flow rate. Remember, that maximum thrust figures are usually given as static sea level thrust. The way the thrust curve drops with altitude and airspeed depends on how you choose to move that flow rate through your engine. Aircraft noise and thrust specific fuel consumption is all about exhaust velocity and exhaust velocity is all about bypass ratio.
 
High speed - specifically supersonic performance - at altitude requires a high exhaust velocity.     
 
Civilian airliners do not require high exhaust velocity for supersonic performance; therefore designers build huge turbofans (high bypass/low exhaust velocity) for maximum subsonic thrust with minimum noise and fuel consumption. Fighter aircraft OTOH require very high exhaust velocity for peak high speed, maneuverability and high altitude performance. Which unfortunately guzzles the fuel and causes noise....lots of noise.


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#149 Victoria Watcher

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Posted 26 December 2018 - 04:53 AM

anybody hear a couple loud bangs around 4:45 am this morning?  i was too asleepish to know what direction they came from. about 15 seconds apart.


Edited by Victoria Watcher, 26 December 2018 - 04:53 AM.


#150 Mike K.

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Posted 26 December 2018 - 10:28 AM

What part of town?
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#151 Victoria Watcher

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Posted 26 December 2018 - 10:39 AM

What part of town?

 

i was too asleepish to know what direction they came from. about 15 seconds apart.

 

 

oh i heard them in the uplands.  but it sounded like a regional noise.


Edited by Victoria Watcher, 26 December 2018 - 10:41 AM.


 



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