Forum: F-35 Lightning II

+10 dB is 10 times the power (e.g. a 100 Watts amplifier Vs a 10 Watts amplifier). 10 times the power gives a perception of doubled (2x) loudness... (AFAIK) Rolling Eyes

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Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

As Bunny said, dB is a logarithmic scale. In relative terms, +3dB is roughly double. 10^(3/10) = 1.995.

@ Guysmiley

I may be mistaken but;
+3 dB means 2x the power NOT the sound pressure. Sound pressure goes with the square root of the power and it is the sound pressure our ears perceive.

BTW, I NEED to check. It has been long time Rolling Eyes

Huh?

What.....?

Wear double hearing protection at any rate; The F135 will be loud enough to render you deaf long before retirement!

TEG

I don't particularly like posting wikipedia stuff but they do have some good basic stuff at times.

http://en.wikipedia.org/wiki/Sound_level#Sound_pressure_level

The basics of sound and how decibel is defined. I was right, there's a factor and 20 in there.

I do believe I speak for everyone when I say it will sound awesome (if painful). Can't wait for the airshows. I usually about fall over from the noise at air shows because it's just... yeah... in thrust we trust.

Best time is when you have a cold-crisp morning and the air is good and dense.
Not only to you get more power from the engines, but the sound travels so much better through the air... In Love

In thrust we trust! Cheers

TEG

From: http://ergo.human.cornell.edu/studentdo ... tics1.html

Quote:

Sound power is directly proportional to the square of the sound pressure

That is:

Sound Pressure Level (SPC) (dB) = 10 log P21 / P2 0
P20 = standard reference sound pressure squared that represents 0 decibels (= 20 µ Nm2 [microNewtons per m2] or .0002 microbars or 20 µ Pa (micropascals))
p21 = measured sound pressure level.
This equation simplifies to: SPL (dB) = 20 log p1 / p0, which deals directly with sound pressure rather than sound pressure squared.

And

Quote:

PNdB - perceived noise level. An increase of 10 PNdB in sound is equal to doubling its noy value.

That is 10 times the power increase will give a +10 dB (as we all agree) and will be perceived as twice as loud.

edit: Here is one more link: http://www.me.psu.edu/lamancusa/me458/3_human.pdf Below quotation is from page Human Response to Sound 3.2.

Quote:

A 10 dB increase in SPL approximately results in twice the subjective loudness (equivalent to 10 identical sources instead of one).

edit2: Link: http://hyperphysics.phy-astr.gsu.edu/Hb ... ud.html#c1

Quote:

A widely used "rule of thumb" for the loudness of a particular sound is that the sound must be increased in intensity by a factor of ten for the sound to be perceived as twice as loud. A common way of stating it is that it takes 10 violins to sound twice as loud as one violin.

That_Engine_Guy wrote:

Best time is when you have a cold-crisp morning and the air is good and dense.
Not only to you get more power from the engines, but the sound travels so much better through the air... In Love

In thrust we trust! Cheers

TEG

Ahh yes, there is nothing like the sound of two F404's at full AB in -40F. Cool

I always prefered a single F100-PW220, but I have been a dedicated Viper fan since I was 6.

In thrust we trust! Indeed! SO why are we not retro-fitting all our Vipers with the Blk 60 motors?

Simply put the upgrade won't happen due to costs. There have been only 2 major "upgrades" done on Viper motors from what I know.

1. All the USAF (Most FMS) PW-200s were removed and modified with a kit, to make upgraded PW-220(E) engines. The mod did not increase power, but drastically improved reliability and maintainability.

2. Block 42 units in the ANG upgraded from PW-220 engines to PW-229 engines. The move made the Block 42s more common with the Block 52s and increased the performance of the 42 so that they are on the same level as the 40/50/52. (Better actually if you run the thrust/weight numbers...)

The GE F110 family requires more airflow than the PW F100 family. If you wanted to put GE-132s in any Pre-25,25,32, or 42 the aircraft's inlet would require replacement to increase airflow.

On the other hand the PW-229 was designed with the same airflow requirements as the PW-200 so that by installing it in a Block 5, you would receive the same amount of thrust as a Block 52 without changing inlets.

Keep 'em flyin' Thumb

TEG

Block 5 airframe with Block 52 thrust? TEG, now your talking my language! Just kidding. I was only asking that question as a joke. I know that the almighty dollar rules all. I can still dream of what the power would be like though cant I?

sprstdlyscottsmn wrote:

Block 5 airframe with Block 52 thrust?

I'd take a Block 25 with a PW-229! Talk about a rocket!

Last I checked a new F100-PW-229 ran about $5M...

I'm sure an F110-GE-129 runs about the same? Shrug

Then there is the tooling upgrades, training requirements, aircraft modifications etc... The whole "re-engine" budget snowballs. Makes the whole program much more than just the cost of X engines times $5M! Shocked

Keep 'em flyin' Thumb

TEG

You know, I never though about that aspect. An initially $15-20 million fighter suddenly becomes a $25-30 million fighter just so that we can say its more fun...

r2d2 wrote:

@ Guysmiley

I may be mistaken but;
+3 dB means 2x the power NOT the sound pressure. Sound pressure goes with the square root of the power and it is the sound pressure our ears perceive.

BTW, I NEED to check. It has been long time Rolling Eyes

That is equal for a 40% wider distance with the equal sound pressure of a F-15, that make a much greater footprint and increase your immovables crisis further more.

BLAST is the word gentleman, the louder the better. I can't wait to hear the
F-35's motor in full blower or MIL power. In my past experiences, the loudest all around (all aspects) was the black smoke belching -79s that powered some F-4Es around my house, while the loudest in dBs from certain aspects and ranges was the F-14D in full blower.

JetBLAST16

Forum: F-35 Lightning II

F-35 twice as loud as the F-15!