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Afterbuners shouldn't be louder than mil power.


mytai01
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I know I'll get disagreement, but I've seen plenty of fighters and I haven't been able to tell any increase in noise when they go from full military power into afterburner. It's a myth! Jet engines don't get any louder than military power...with or without afterbuners on. It's annoying to watch a DCS video I've made and hearing the afterburner in the game going on and off. You won't hear that effect in a real airshow!

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I know I'll get disagreement, but I've seen plenty of fighters and I haven't been able to tell any increase in noise when they go from full military power into afterburner. It's a myth! Jet engines don't get any louder than military power...with or without afterbuners on. It's annoying to watch a DCS video I've made and hearing the afterburner in the game going on and off. You won't hear that effect in a real airshow!

 

Stay away from airshows. Burner is A LOT louder than mil. Try standing 5 feet from the nozzle w/a 30 foot blowtorch come out of it.

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Chris

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I'm a Navy brat,

I've been to at least 3 Airshows a Year for 28 years,

I've been on the Carrier for Family Cruises.

I've been on Base and in the Hanger nearly everyday after school.

I've watched F-14s, F-18s, A-6s, A-7s, fly over my house for the last 25 years.

 

And I can tell you without a Doubt, that when a plane lights the burners, it is Significantly louder.

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I am curious as to what aircraft, at what distance, the OP is referring to.


Edited by cichlidfan

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I know I'll get disagreement, but I've seen plenty of fighters and I haven't been able to tell any increase in noise when they go from full military power into afterburner. It's a myth! Jet engines don't get any louder than military power...with or without afterbuners on. It's annoying to watch a DCS video I've made and hearing the afterburner in the game going on and off. You won't hear that effect in a real airshow!

 

you need to go to the doctors and have your ears checked..:thumbup:

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you cant use youtube videos to compare sound, because camera microphones are bad, and they cannot pickup that many decibels (and youtube makes the sound doubly bad).

As an example when someone has a bad microphone and yells, the microphone will keep the soundlevel the same, or it will actually quiet down or just start braking up.

 

Its the same as listening to guns shoot on youtube, you'd think the PKM is a really quite weapon.

 

someguy from youtube

stood about five feet to the right side and forward of two number two engine stage 5 AB runs on the trim pad at during our deployment at Cold Lake, CA in the late 80's. Wore earplug and muffs and it was still pretty loud. No heat feel but the concrete pad vibrated so much that it made my feet ache.

Edited by karambiatos
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Mytai is actually correct...

 

i dont think so

maybe its depends of aircrafts/engines but the afterburner is noticeably louder than the full mil

we can measure the decibels and the sound pressure level with spec instruments (not with a microphone), yep, youtube videos are not good examples but here are another two

 

at 2:15

http://www.youtube.com/watch?v=df3vW5HsPlc#t=135

 

at 6:35


Edited by NRG-Vampire

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From an engineering standpoint, it would be extremely surprising if reheat didn't turn up the volume, since it significantly increases the speed and mass flow of fluid exiting the engine. If i'm not mistaken, reheat will even cause the flow to go supersonic on most designs.

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12 years on flightlines with F-4's, F16's, F15's, and especially B-1's, tell me that there is a perceptible difference in the loudness.

 

According to the Navy, the F15 has 144 db in Mil power and 149 db in afterburner. For acoustics, 10 db is the doubling factor, so the F15 is half again as loud in afterburner.

 

Chart from document below:

 

5fs1aAS.jpg

 

http://www.nrac.navy.mil/docs/2009_FINAL_Jet_Noise_Report_4-26-09.pdf



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i dont think so

maybe its depends of aircrafts/engines but the afterburner is noticeably louder than the full mil

we can measure the decibels and the sound pressure level with spec instruments (not with a microphone), yep, youtube videos are not good examples but here are another two

 

at 2:15

http://www.youtube.com/watch?v=df3vW5HsPlc#t=135

 

at 6:35

 

:thumbup:

 

12 years on flightlines with F-4's, F16's, F15's, and especially B-1's, tell me that there is a perceptible difference in the loudness.

 

According to the Navy, the F15 has 144 db in Mil power and 149 db in afterburner. For acoustics, 10 db is the doubling factor, so the F15 is half again as loud in afterburner.

 

 

Nice chart. After I watched those youtubes I thought back to when I was doing real time reads while the motor was in burner and at mil power the motor is pretty loud. You can notice a slight increase in sound. I think the further away the more its noticeable.

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Chris

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:thumbup:

Nice chart. After I watched those youtubes I thought back to when I was doing real time reads while the motor was in burner and at mil power the motor is pretty loud. You can notice a slight increase in sound. I think the further away the more its noticeable.

 

 

When we started working with B-1's, we had to add locking rods to our bookshelves with all the T.O.'s in them. They would literally vibrate the books out of the shelf with AB takeoffs. IIRC correctly, we were about 400' from centerline.



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http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CDgQFjAE&url=http%3A%2F%2Fwww.nrac.navy.mil%2Fdocs%2F2009_FINAL_Jet_Noise_Report_4-26-09.pdf&ei=qoqcU-iDDsqsyATRvIDwAw&usg=AFQjCNEVKJJaBIgCFr_WjDcGR9SzYDaCXA&bvm=bv.68911936,d.aWw&cad=rja

 

"Afterburners increase the jet noise levels by 5 to 10 dB above military power." (remember decibels are a log scale measurement)

 

Can't judge noise level from a video without knowing the cut off frequencies of the camera's microphone and digital compression method. Additionally it is likely the microphone and amplifier are simply saturated. They are meant to pick up human speech not deafness inducing noise fields.

My computer system just isn't up to the task of generating the low frequency power of an jet engine in afterburner, so as a compromise I imagine DCS's sound editor just adjusted the overall sound to be louder in afterburner. Much easier and cheaper then keeping a jet engine in your room for sound effect purposes.

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When we started working with B-1's, we had to add locking rods to our bookshelves with all the T.O.'s in them. They would literally vibrate the books out of the shelf with AB takeoffs. IIRC correctly, we were about 400' from centerline.

 

I worked at Boeing in Wichita adjacent to McConnell AF base in the 80s when they got the B-1b's. It was funny to hear all the car alarms going off in the parking lot when a B-1 did an afterburner takeoff.

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For acoustics, 10 db is the doubling factor, so the F15 is half again as loud in afterburner.

 

If talking SPL:

 

20*log10(2) ~= 6dB

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I worked at Boeing in Wichita adjacent to McConnell AF base in the 80s when they got the B-1b's. It was funny to hear all the car alarms going off in the parking lot when a B-1 did an afterburner takeoff.

 

I was across the runway from you then, about the '87/'88 time frame. Right in the middle between the taxiway and the runway.



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If talking SPL:

 

20*log10(2) ~= 6dB

 

 

I think it varies depending on what is being measured?

+3db measured power is double, +6 db measured voltage is doubled, and +10 db measured sound is double.



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I know I'll get disagreement, but I've seen plenty of fighters and I haven't been able to tell any increase in noise when they go from full military power into afterburner. It's a myth! Jet engines don't get any louder than military power...with or without afterbuners on. It's annoying to watch a DCS video I've made and hearing the afterburner in the game going on and off. You won't hear that effect in a real airshow!

 

The Concorde wasn't allow to use afterburners over rural areas because of the sonic boom AND the dramatically louder engines running on burner.

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