The F-35 is twice as loud as the F-15 Eagle.

[stigmata]

Interestingly, noise is more damaging if you dont like it vs something you do like, like a concert for ex, despite having same decibel.

 

[SlyDog]

Interesting subject since I'am hifi-freak.

First after a reading at wiki, to be sure on definitions.

Sound pressure level (SPL) or sound intensity are thing I often be confused about

An increase of 3 dB is the same as a doubled sound intensity

An increase of 6 dB is the same as a doubled Sound pressure level (SPL)

The ear "compress" the sound somewhat. So therefore the sound have to increase between 6-10 dB - to be perceived as a doubled Sound pressure level (SPL). It depends both on sound level and frequency.

There is a unit for subjective (percived) sound level: Phon.

http://en.wikipedia.org/wiki/Phon

The phon was proposed as a unit of perceived loudness level LN for pure tones[1] by S. S. Stevens. The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones.[2] By definition, 1 phon is equal to 1 dBSPL at a frequency of 1 kHz.


Add: Double the distance from the source will reduce the sound level by 6 dB

 

[Dalregementet]

pulled from another loc.

A decibel is defined as 10*log(P1/P0), which means "twice as loud" will add 10*log(2) = 3.01 decibels to the noise level.


So, "Twice as loud" only means another 3 decibels and, since the power of sound decreases with the square of distance, 3 decibels is barely noticeable from far away. If the media stays out of it, I doubt anyone will notice.


quite frankly, some of the arguments getting thrown into the debate are borderline hysterical - the anti-JSF pro-Gripen argument is starting to remind me of the australian anti-JSF pro-Super F111 debate.

ie lots of volume from people outside of those actually involved and contemptuous silence from those who actually have access to the real datasets.

It´s the people who live near a military airfield that has to hear the noise. If an increase of 10 Db is percieved as double up then it´s that perception that is important - nothing else. Using words like "borderline" and "hysterical" is condescending to other participants.

 

[gf0012-aust]

It´s the people who live near a military airfield that has to hear the noise. If an increase of 10 Db is percieved as double up then it´s that perception that is important - nothing else. Using words like "borderline" and "hysterical" is condescending to other participants.

Unfortunately my real life work experience is that a significant quantum of noise by people on issues like this is exacerbated by a number of things:

• the science proclaimed to support their position is completely misunderstood or misrepresented (we have 30 years of experience with F-111, The Collins, Abrams and even the JSF are standout examples)
• that the actual number of people who have first hand knowledge and claim to be subject matter experts is close to zero - (funnily enough they also usually have conflicts of interest)
• opponents are prepared to outright lie to establish an arguing beach-head

so yes, perception can be truth - and thats why the shrill noises that get generated needed to be dealt with properly to show that there could be some significant flaws in what they've been led to believe and now firmly accept as fact.

if you have never experienced any of the above then you live in a country where they obviously don't have newspaper journalists or a newspaper.

As far as I'm concerned, I'm more than happy to counterbalance hysteria with fact so that the naysayers don't get a free ride off the coat-tails of the general publics interest.

Just out of interest, whats on the public record for people lodging noise complaints after Harriers took off from airfields? (because Harriers have been in Sweden a number of times). I'd wager a bet - absolutely none, nada, zip, ziltch.
So immediately I question whether you then have purpose built complaints.

I'd hazard a guess that if it was a Gripen sounding like a portable rock concert rotating out that there would be some vicious rearguard defence of it in play. We'd see the same numbers being trotted out to show that people within "nn" hundred meters don't see/"hear" a doubling of noise at all.

I've come across this before with opponents of wind turbines. pseudo professionals citing "unavailable" references (in some cases outright fabrications) have claimed that wind turbines at speed will be excessively noisey.

the problem being that the speeds that they claim would generate supersonic tip speed noise never occur because the turbines are electronically goverened, the turbines also have to meet an international db standard (to get covered by insurance - and all wind turbines have to meet 1 of 2 internationally approved and recognisedaccreditations). Noisey turbines also apparently means that cows will give birth to 5 legged and 3 headed calves. Yet, in all my engineering assessments and tech review travels in Germany, France, Denmark, Spain, UK, Netherlands I never saw or spoke to any farmers or vetinareans who'd seen animal defects.

in other words, people will believe what they want when it suits their purpose.

thats why psychologists win both ways....