Airbus Claims that A350XWB is quieter than B787, but is it really?

keesje · Fri Jun 29, 2018 2:47 pm

masi1157 wrote:
keesje wrote:
Let's get the app's & get it over with. Sidelining the OE marketing departments as we should always do.

So you are expecting reasonable results from a bunch of people that don't really know what they are doing, using a wide variety of smartphones (and apps on their smartphones) producing uncalibrated and widely scattering readings, without knowing what the aircraft they are sitting in is currently doing, how it differs from the aircraft of the same type that somebody else tried to "measure", and don't know what it should be like and what it should be doing to produce comparable results? Enjoy!

I can tell you, you will find levels varying by easily 3 dB(A) or more measured by professionals with professional equipment at the same position on 2 aircraft that should have been (from all the parameters you can control and compare) exactly identical in terms of cabin noise. It is just aircraft to aircraft (or even flight to flight on the same aircraft) scattering. And it can be 20 dB(A) and more if you only compare different locations and/or flight conditions on those 2 "identical" aircraft. So how many data sets do you want to collect before you come to any reliable conclusion? It will be hundreds if not thousands just to find a tendency comparing aircraft type A to type B.

keesje wrote:
Unless some doesn't like the answer. Then again w'll see attempts to discredit, confuse, demand sources, dismiss as AvsB, generalize, false comparisons, strawman's etc.

Is that the game you want to play? Then play it without me. I very much hope your bunch of "test data" will be looked at very very critically by somebody else then. Btw, I am as critical with that "6 dB quieter" claim. But it seems nobody else but the TO ever saw or heard that anywhere and can tell us, what that claim was all about.

Gruß, masi1157

I'm convinced we can work out something with an app. If many people have it, do the measurement, log the flight number, seatnumber, time, cruise attitude that might be a start. (FGS put it in aircraft mode first if an FA asks :wink2:

) After getting a few 100k measurements, we can do the statistics, we might have a reasonable results, including margins. Maybe seatguru.com can jump in, adding it to their app. The power of the masses that has been changing everything, for better or worse.

I just got https://play.google.com/store/apps/details?id=coocent.app.tools.soundmeter.noisedetector&hl=en_US & will test in the upcoming weeks (lots of flights). It's a fun app to have :veryhappy:

. In the end we need all the same calibrated tool & instructions. I just sneezed, 82db.. Over the last 11 minutes my average was 59db, max 82 (sneeze, min 38db).

trauha · Fri Jun 29, 2018 9:16 pm

masi1157 wrote:
trauha wrote:
...it was so quiet that the couple talking behind me was so clear that it was disturbing, since no noise was there to drown out their voices.

Are you also disturbed when you sit in a restaurant and hear people talking on the next table? Or is it just that you are used to it in a restaurant, but not on an aircraft? I can tell you that it is still much too noi sy in any modern aircraft, most of them easily above 70 dB(A) during cruise, especially when compared to modern cars or high-speed trains.

Gruß, masi1157

In a restaurant the people at the next table are not 32 inches from my ear. Distance makes a big difference as dB decrease logarithmically with distance. In a restaurant many voices blend into a mix of sound. It is more disturbing if there is only one loud table.

LAXLHR · Fri Jun 29, 2018 11:21 pm

Waterbomber wrote:
I've flown the A350-900 and B788 back to back within 4 days on long haul flights and I'm not happy to read the Airbus claim that the A350 is 6 decibels quieter than the B787.
The B787 definitely is a lot quieter than the A350. Also, the A350-900 that I flew on (AY) had a piece of paper tissue between the side panels to remind me that I sat in that exact same plane and exact same seats a few months ago. Indeed, I slid that piece of tissue because the side panels were vibrating against eachother to produce the unbearabale rattling sound. The same issue can also be found on their window paneling.

I really wonder how Boeing could make the B787 so quiet in the cabin.

IMO Airbus' claim is incorrect and they really need to get those rattling cabin furnishings worked out.
I also hope that Boeing applies lessons from the B787 to the B777X to make it at least as quiet as the A350.

It's called grand standing and marketing.

"I'm not happy" I'm sooooooo sorry that this is going to ruin your weekend! SMH!!! Guess what. It doesn't really matter. Be worried about the 60 volcanoes currently erupting around the world and the impact (i guess) on air traffic, than this nonsense of Airbus vs Boeing. Delta vs (the world - in stupid people's minds) etc. It's dumb! They are both quieter planes than the rest, thats all!

masi1157 · Sat Jun 30, 2018 8:14 pm

keesje wrote:
I'm convinced we can work out something with an app.

Some people believe in "big data", others don't, including me (for aircraft interior noise purposes, not generally). I've spent too much time trying (and failing) to extract useful information from recordings made by people that knew what they were doing (again including myself) with professional and well calibrated equipment during flights, that virtually any relevant parameter were known of.

trauha wrote:
Distance makes a big difference as dB decrease logarithmically with distance.

They don't. In a freefield environment they drop by 6 dB per doubling the distance, further away friom the source in the reverberant field they stay more or less constant. But that will take us too far off.

The important part was given by Thomas much earlier: Conversations from the next table or the next seat row might draw your conscious attention, but they are completely irrelevant for fatigue. The masking noise that you seem to desire on an aircraft (which is usually well above 70 dB(A)!) doesn't draw your attention, buit basically ruins your health and especially that of the crew working in that environment.

Gruß, masi1157

Planesmart · Sat Jun 30, 2018 9:33 pm

As someone who can recall flying on the BAC111, VC10, Trident, 727, Comet, 707 and 737-100, I'm glad in hindsight, they didn't have the range for the long range flights possible today.

There was a step change with the arrival of the 747, DC10 & Tristar, especially if you could select your seat with engine noise in mind.

Then there appeared to be many small, incremental improvements with new models, although during this period, I thought perhaps my hearing was less acute.

And then came the A380, and that was another step change, though as some say, it's over engineered, so perhaps the quiet is an accidental by-product. Sorry Boeing, but the 748 isn't in the game.

There is no way the 787 and A350 are quieter than the A380. The A380 is noticeably quieter than both, although perhaps there are seats on both where they match.

Both 787 and A350 seem similar (haven't been on the 1000), though the tone and oscillations differ slightly. If unlucky enough to fly in economy, quieter cabins means you can hear every moan and groan from passengers in front, behind and beside. Amazing how the discomfort of others can impact your enjoyment of a flight.

In that respect, those squeezing more seats into 787's might want to increase aircraft and engine noise, not reduce it any further.

caljn · Sat Jun 30, 2018 9:46 pm

itisi wrote:
The vote is in. The A350 is the quietest!

Friend flew on both, he's a 777 captain... and too my surprise he said as a passenger he likes the A350 more

Well there you have it then! Subjective, anecdotal evidence closes the discussion! Move along folks, nothing to see here.

keesje · Sat Jun 30, 2018 11:17 pm

The db meter installed on smartphone, there is a calibration function. I will see if I can calibrate it somewhere. It takes at least 10-data points per second. I will try walk up and down the aisle and take the average after 5 munites / a few thousands measurements. So peeks are averaged out. And do that a few times at cruise level. Over the next 2 weeks I will fly A333 (PW), MD90, 753 (PW), 738 and 772ER (GE). Lets see if this works.

JAAlbert · Sun Jul 01, 2018 12:05 am

I'm just so darned mad that I haven't flown on either plane yet! Not that this should stop me from weighing in on the topic :lol:

Anyways, everything I've read is that the planes are noticeably quieter than the previous generation of planes. I took a 767 to Athens recently and the cabin noise was so loud I couldn't hear my partner who was sitting next to me. I've found that cabin noise is one of the big sources of fatigue for me on a long haul flight. Any aircraft that offers a quieter cabin is my automatic new favorite plane!

HoboJoe · Sun Jul 01, 2018 12:07 am

either way what difference would it make - another straw AB is grabbing at

wallybird · Sun Jul 01, 2018 12:53 am

Ah, for the days of sitting forward of the wing on a B727-200; takeoff, cruise and landing.

DocLightning · Sun Jul 01, 2018 7:54 am

One issue with the 787 that I really wish Boeing would fix is that godawful hydraulic pump just at the aft part of the wing. I makes the most tooth-grinding high-pitched squeal. At the front and aft, it's not so loud. It's active during various parts of taxi, most of takeoff until flaps are up, and landing from the time the flaps start to extend.

Seriously, Boeing, you couldn't have done something about it?

masi1157 · Sun Jul 01, 2018 8:58 am

keesje wrote:
The db meter installed on smartphone, there is a calibration function. I will see if I can calibrate it somewhere.

You can't properly calibrate those things. Even professional equipment is usually calibrated at just one frequency and one level (usually 94 dB @ 1 kHz or 124 dB @ 250 Hz). But that equipment has a well defined spectral and signal linearity (100 dB at 100 Hz and 8 kHz would both read "100 dB", and 50 dB and 120 dB would read "50 dB" and "120 dB"). They have defined directivity, very low drift, very low sensitivity to vibration, are stable over time, temperature, humidity, ambient pressure and more and more. Smartphones don't.

And even if they were usable as acoustic test devices, how do you make sure everybody uses them properly and the same way? Where, how and what shall they measure? Where do they get all the parameters from that influence cabin noise levels? They are many many more than just speed and altitude (but even those you can't read correctl from the IFE, if installed at all). And finally, how do you compare? Was the reading in aircraft X higher than in Y because of any of those many parameters, or really because X is noisier than Y?

keesje wrote:
Lets see if this works.

You will get a lot of numbers. They might even be in the expectable range. But you won't be able to say why the numbers are as they are.

Gruß, masi1157

oslmgm · Sun Jul 01, 2018 9:21 am

masi1157 wrote:
keesje wrote:
The db meter installed on smartphone, there is a calibration function. I will see if I can calibrate it somewhere.

You can't properly calibrate those things. Even professional equipment is usually calibrated at just one frequency and one level (usually 94 dB @ 1 kHz or 124 dB @ 250 Hz). But that equipment has a well defined spectral and signal linearity (100 dB at 100 Hz and 8 kHz would both read "100 dB", and 50 dB and 120 dB would read "50 dB" and "120 dB"). They have defined directivity, very low drift, very low sensitivity to vibration, are stable over time, temperature, humidity, ambient pressure and more and more. Smartphones don't.

And even if they were usable as acoustic test devices, how do you make sure everybody uses them properly and the same way? Where, how and what shall they measure? Where do they get all the parameters from that influence cabin noise levels? They are many many more than just speed and altitude (but even those you can't read correctl from the IFE, if installed at all). And finally, how do you compare? Was the reading in aircraft X higher than in Y because of any of those many parameters, or really because X is noisier than Y?

keesje wrote:
Lets see if this works.

You will get a lot of numbers. They might even be in the expectable range. But you won't be able to say why the numbers are as they are.

Gruß, masi1157

I love reading your posts! (I studied audio engineering some years ago, so I know a little bit about noise and decibels - enough to appreciate your insight.)

Thank you for posting here on a.net!

keesje · Sun Jul 01, 2018 10:13 am

masi1157 wrote:
keesje wrote:
The db meter installed on smartphone, there is a calibration function. I will see if I can calibrate it somewhere.

You can't properly calibrate those things. Even professional equipment is usually calibrated at just one frequency and one level (usually 94 dB @ 1 kHz or 124 dB @ 250 Hz). But that equipment has a well defined spectral and signal linearity (100 dB at 100 Hz and 8 kHz would both read "100 dB", and 50 dB and 120 dB would read "50 dB" and "120 dB"). They have defined directivity, very low drift, very low sensitivity to vibration, are stable over time, temperature, humidity, ambient pressure and more and more. Smartphones don't.

And even if they were usable as acoustic test devices, how do you make sure everybody uses them properly and the same way? Where, how and what shall they measure? Where do they get all the parameters from that influence cabin noise levels? They are many many more than just speed and altitude (but even those you can't read correctl from the IFE, if installed at all). And finally, how do you compare? Was the reading in aircraft X higher than in Y because of any of those many parameters, or really because X is noisier than Y?

keesje wrote:
Lets see if this works.

You will get a lot of numbers. They might even be in the expectable range. But you won't be able to say why the numbers are as they are.

Gruß, masi1157

Hi thnx. I will use the same tool under same conditions and the same way. I will collect the data, exactly explaining what I did. So comparitive data more than exact dB measurements. Let alone looking at the spectrum / sources. The mechanics useally are that this kind of observations triggers action by interest groups nothing liking the results. They then need to do a better job to counter the innitial conclusions. And that is of course a good thing / progress. :highfive:

masi1157 · Sun Jul 01, 2018 11:27 am

keesje wrote:
And that is of course a good thing / progress.

It would be a good thing if somebody with the necessary expertise using appropriate test equipment would seriously investigate the matter to falsify or verify a statement. But as it stands that would not be the case. Even more, it seems nobody else but the TO ever heard of that statement to be falsified/verified here. So any interest group seeing this should simply not care and not react at all. I personally don't care about whatever numbers you come up with, they are meaningless. But I would not like, if you start drawing any conclusions from them that the numbers and the way they were produced can't support.

I will stop that discussion here, enough repeating the same stuff again and again. Enjoy your "test campaign", but only publish the results, if you are absolutely certain the numbers are meaningful. And be extremely careful with any conclusion you draw from them.

Gruß, masi1157

OldAeroGuy · Sun Jul 01, 2018 10:23 pm

masi1157 wrote:
We have been talking about "quieter" in this thread, and that is what I asked you. So what did Airbus claim about the A350 being quieter, who said that and where can we read what he said?

Gruß, masi1157

Item 9 in this Airbus publication http://www.airbus.com/content/dam/corpo ... res-EN.pdf
claims that the A350 cabin noise is up to 4 times less than the 787.

birdbrainz · Sun Jul 01, 2018 10:37 pm

All of this going on about wanting a quiet aircraft... Its very odd that I've slept best (and enjoyed my flights the most) on Dash-8s (while wearing my Bose headphones).

I thought it was a fluke until on a Delta 717 way in the back, and noticed exactly the same thing: the more noise, the easier it is to tune out everything and fall asleep. Go figure.

M564038 · Sun Jul 01, 2018 11:03 pm

Another sound engineer here.
There will not be data gained with any meaning from any of the «methods» suggested in this thread. Sorry.

keesje · Mon Jul 02, 2018 6:17 am

Yes I will :wink2:

just not on the 78 & XWB.

There is a strong mutual interest between OE's and airlines to not effectively communicate on typical passenger comfort topics. Mainly because airlines have to deal with what they have invested in and can't do much / don't want increase costs. The OE's made the decisions long ago & just want to sell aircaft & keep airlines happy. Only large passenger group (shifts) sizeable negative PR and authorities can change things.

masi1157 · Mon Jul 02, 2018 6:51 am

OldAeroGuy wrote:
...claims that the A350 cabin noise is up to 4 times less than the 787.

"4 times less noise"? :roll:

I better don't comment on that.

Gruß, masi1157

oslmgm · Mon Jul 02, 2018 8:59 am

masi1157 wrote:
OldAeroGuy wrote:
...claims that the A350 cabin noise is up to 4 times less than the 787.

"4 times less noise"? I better don't comment on that.

Gruß, masi1157

lol yes... I was wondering what that could mean - I was thinking maybe "4 times less" could mean -12 dB, but it's just weird. Maybe it's a bad translation from French, and they meant to say that there is less noise in the cabin up to 4 times during a flight. (At the gate, during taxiing, etc.) :mrgreen:

zeke · Mon Jul 02, 2018 10:11 am

oslmgm wrote:
lol yes... I was wondering what that could mean - I was thinking maybe "4 times less" could mean -12 dB, but it's just weird. Maybe it's a bad translation from French, and they meant to say that there is less noise in the cabin up to 4 times during a flight. (At the gate, during taxiing, etc.)

4 times louder is hardly noticeable by the human ear, for example if the A350 cabin noise was measured at 55 dB, which is log base 10 (noise) = 55, the noise level would be 10 to the power of 55 (10^55) = 1*10^55, four times higher is 4*10^55= 4*10^55 on the log scale it is log base 10 (4*10^55)=55.6 dB.

The difference beeeen 55 and 55.6 dB would not be noticeable to the human ear but can be measured.

masi1157 · Mon Jul 02, 2018 10:12 am

zeke wrote:
4 times louder is hardly noticeable by the human ear, for example if the A350 cabin noise was measured at 55 dB, which is log base 10 (noise) = 55, the noise level would be 10 to the power of 55 (10^55) = 1*10^55, four times higher is 4*10^55= 4*10^55 on the log scale it is log base 10 (4*10^55)=55.6 dB.

The difference beeeen 55 and 55.6 dB would not be noticeable to the human ear but can be measured.

If you can't calculate in dB, better don't try!

A factor 4 in sound pressure would mean a 12 dB difference. A factor 4 in sound power (resp. sound intensity or, in a reverberant field like an aircraft cabin, sound energy density) means 6 dB. A factor 4 in noise perception (by humans) would require almost 20 dB. I am afraid somebody mistook a 6 dB difference meaning "4 times the sound power" as "4 times as noisy", but that would be straight nonsense.

Gruß, masi1157

oslmgm · Mon Jul 02, 2018 10:31 am

masi1157 wrote:
zeke wrote:
4 times louder is hardly noticeable by the human ear, for example if the A350 cabin noise was measured at 55 dB, which is log base 10 (noise) = 55, the noise level would be 10 to the power of 55 (10^55) = 1*10^55, four times higher is 4*10^55= 4*10^55 on the log scale it is log base 10 (4*10^55)=55.6 dB.

The difference beeeen 55 and 55.6 dB would not be noticeable to the human ear but can be measured.

If you can't calculate in dB, better don't try!

A factor 4 in sound pressure would mean a 12 dB difference. A factor 4 in sound power (resp. sound intensity or, in a reverberant field like an aircraft cabin, sound energy density) means 6 dB. A factor 4 in noise perception (by humans) would require almost 20 dB. I am afraid somebody mistook a 6 dB difference meaning "4 times the sound power" as "4 times as noisy", but that would be straight nonsense.

Gruß, masi1157

Right. Probably a 6 dB difference measured at some point somewhere, and someone had no clue how to use that not-very-useful information.

zeke · Mon Jul 02, 2018 10:57 am

masi1157 wrote:

A factor 4 in sound pressure would mean a 12 dB difference. A factor 4 in sound power (resp. sound intensity or, in a reverberant field like an aircraft cabin, sound energy density) means 6 dB. A factor 4 in noise perception (by humans) would require almost 20 dB. I am afraid somebody mistook a 6 dB difference meaning "4 times the sound power" as "4 times as noisy", but that would be straight nonsense.

No, 12 dB is 20xlog(ratio) it’s the same method used to calculate the voltage ratio in a circuit, likewise to work out the power gain in a circuit is is 10xlog(ratio). The snippet says nothing about sound pressure, power, intensity etc they are words you are adding to their statement. They also said nothing a factor of 4 in noise perception.

oslmgm · Mon Jul 02, 2018 11:07 am

zeke wrote:
masi1157 wrote:

A factor 4 in sound pressure would mean a 12 dB difference. A factor 4 in sound power (resp. sound intensity or, in a reverberant field like an aircraft cabin, sound energy density) means 6 dB. A factor 4 in noise perception (by humans) would require almost 20 dB. I am afraid somebody mistook a 6 dB difference meaning "4 times the sound power" as "4 times as noisy", but that would be straight nonsense.

No, 12 dB is 20xlog(ratio) it’s the same method used to calculate the voltage ratio in a circuit, likewise to work out the power gain in a circuit is is 10xlog(ratio). The snippet says nothing about sound pressure, power, intensity etc they are words you are adding to their statement. They also said nothing a factor of 4 in noise perception.

zeke: When it comes to piloting, I listen to what you say, knowing that you're a professional pilot. I know that I can learn from your insight.
As far as I know, cabin noise is masi1157's profession, so maybe you can learn something from him...? (Looking at your decibel calculations, I'm pretty sure you can!)

zeke · Mon Jul 02, 2018 11:15 am

oslmgm wrote:

zeke: When it comes to piloting, I listen to what you say, knowing that you're a professional pilot. I know that I can learn from your insight.
As far as I know, cabin noise is masi1157's profession, so maybe you can lean something from him...? (Looking at your decibel calculations, I'm pretty sure you can!)

Problem is they are trying to come across as being smart, and failing. The comment says nothing about the acoustic power at source, sound pressure or sound intensity. I’ll be the first to eat my hat when it can be shown that is what Airbus stated.

“up to 4 times less noise” is all that was mentioned in a marketing document, not 4 dB less noise, not 12 dB less noise.

masi1157 · Mon Jul 02, 2018 11:22 am

zeke wrote:
No, 12 dB is 20xlog(ratio) it’s the same method used to calculate the voltage ratio in a circuit, likewise to work out the power gain in a circuit is is 10xlog(ratio).

You know the definition of sound pressure level?

zeke wrote:
The snippet says nothing about sound pressure, power, intensity etc they are words you are adding to their statement. They also said nothing a factor of 4 in noise perception.

Is it so hard to understand that I simply tried to interpret what might have been ment with "4 times less noise" and where that misunderstanding might have come from?

Gruß, masi1157

zeke · Mon Jul 02, 2018 11:27 am

oslmgm wrote:
So when an Airbus expert on cabin noise tells you that "up to 4 times less noise" is a pretty meaningless statement, you still don't care?

No, I know they would have measured it to come up with the statement, but would a human actually be able to tell the difference, doubtful. Much like the claims we saw on the 787 regarding cabin altitude and humidity when they were already in service with other aircraft, just useless claims for dumb newspapers and magazines to use not knowing what it actually means or if it matters.

It’s marketing, not science !!!!

oslmgm · Mon Jul 02, 2018 11:27 am

zeke wrote:
oslmgm wrote:

zeke: When it comes to piloting, I listen to what you say, knowing that you're a professional pilot. I know that I can learn from your insight.
As far as I know, cabin noise is masi1157's profession, so maybe you can lean something from him...? (Looking at your decibel calculations, I'm pretty sure you can!)

Problem is they are trying to come across as being smart, and failing. The comment says nothing about the acoustic power at source, sound pressure or sound intensity. I’ll be the first to eat my hat when it can be shown that is what Airbus stated.

So when an Airbus expert on cabin noise tells you that "up to 4 times less noise" is a pretty meaningless statement, you still don't care?

PlymSpotter · Mon Jul 02, 2018 11:36 am

To take a slightly different view on this thread, I live close to LGW and spend a lot more time under these aircraft than I do in them. The A359 appears consistently quieter than the 787-8/-9 when overflying on departure.

EASA offer a series of certification data sheets on the noise for approach, lateral and flyover which offer good insight, for example:

A350-941 - 86.3dB flyover EPNL (@ 277,000kg with Trent XWB-84)
A350-1041 - 88.3db flyover EPNL (@ 308,000kg with Trent XWB-97)

B787-8 - 88.3dB flyover EPNL (@ 227,930kg with GEnx-1B64/P1G01)
B787-8 - 87.7dB flyover EPNL (@ 227,930kg with Trent 1000-A/01)
B787-9 - 91.1dB flyover EPNL (@ 249,475kg with GEnx-1B67/P2G01)
B787-9 - 89.6dB flyover EPNL (@ 254,011kg with Trent 1000-D2)

oslmgm · Mon Jul 02, 2018 11:39 am

zeke wrote:
oslmgm wrote:
So when an Airbus expert on cabin noise tells you that "up to 4 times less noise" is a pretty meaningless statement, you still don't care?

No, I know they would have measured it to come up with the statement, but would a human actually be able to tell the difference, doubtful. Much like the claims we saw on the 787 regarding cabin altitude and humidity when they were already in service with other aircraft, just useless claims for dumb newspapers and magazines to use not knowing what it actually means or if it matters.

It’s marketing, not science !!!!

Are you still saying that "4 times less noise" could be the difference between 55 dB and 55,6 dB? (Since you're saying it's doubtful that a human can tell the difference.)

zeke · Mon Jul 02, 2018 12:21 pm

masi1157 wrote:
You know the definition of sound pressure level?

Sure, I understand the difference between acoustic power, sound intensity, and sound pressure. Sound pressure level is the sounds pressure referenced normally to 2x10^-5 N/m^2, the nominal sensitivity of the human ear at 1000 Hz (but purists say it should be more like 2.5).

masi1157 wrote:
Is it so hard to understand that I simply tried to interpret what might have been ment with "4 times less noise" and where that misunderstanding might have come from?

As did I, just interpreted the statement a different way.

oslmgm wrote:
So when an Airbus expert on cabin noise tells you that "up to 4 times less noise" is a pretty meaningless statement, you still don't care?

I wouldn’t expect an expert in the field to make such a comment, they would always state the appropriate units and conditions. I just saw a two page marketing blurb which is basically meaningless for any sort of technical comparison.

http://www.airbus.com/content/dam/corpo ... res-EN.pdf

oslmgm wrote:
Are you still saying that "4 times less noise" could be the difference between 55 dB and 55,6 dB? (Since you're saying it's doubtful that a human can tell the difference.)

It is one possible interpretation of what they were saying, but not the only way !!!

masi1157 · Mon Jul 02, 2018 12:28 pm

zeke wrote:
oslmgm wrote:
Are you still saying that "4 times less noise" could be the difference between 55 dB and 55,6 dB? (Since you're saying it's doubtful that a human can tell the difference.)

It is one possible interpretation of what they were saying, but not the only way !!!

No! That one is not a possible interpretation, it is just wrong.

Gruß, masi1157

zeke · Mon Jul 02, 2018 12:40 pm

masi1157 wrote:
No! That one is not a possible interpretation, it is just wrong.

That is because of the way you were brought up, try thinking a little left or right .....

https://www.expatica.com/de/insider-vie ... 04308.html

masi1157 · Mon Jul 02, 2018 12:54 pm

I can look wherever I want, the difference between 55 dB and 55.6 dB is nowhere even close to 4 times of anything related to noise.

Gruß, masi1157

zeke · Mon Jul 02, 2018 1:14 pm

masi1157 wrote:
I can look wherever I want, the difference between 55 dB and 55.6 dB is nowhere even close to 4 times of anything related to noise.

They said it is quieter !!! You need to take your engineers hat off and understand the “up to” numbers probably have nothing to do with the underlying physics and everything to do with marketing.

It is like the claim “25% step change in fuel efficiency“, does that mean 25% lower fuel flow, or 25% lower block fuel, or 25% smaller tanks, tonnes per hour, liters per minute, liters per 100 km etc., the conditions like takeoff, climb, cruise etc. Another marketing statement without units or conditions which make any sort of technical analysis of it useless.

Which is different to “The A350 XWB is the quietest of all twin-aisle airplanes. Exterior noise level of the A350- 900 is certified at 21 EPNdB (Effective Perceived Noise Decibel) below ICAO Chapter 4 requirements.” which gives you the units and conditions.

masi1157 · Mon Jul 02, 2018 1:25 pm

That is not the point! You made a completely wrong calculation that turned a factor 4 of something into a 0.6 dB difference. That is complete nonsense, and you seem still not to understand why. Therefore I will ignore the rest of your post, it is based on wrong assumptions. And that has nothing to do with me being a german engineer. You should better refrain from comments like that.

Gruß, masi1157

keesje · Mon Jul 02, 2018 1:47 pm

In passenger comfort "if you can't convince them, confuse them" is widely used tactic.

Because of the airline / OE real interests. As dicussed above.

That's why I'll just measure uniformly & reporduce measurements.

A good step ore objectively than personal opinions / preferences that seem leading today.

The OE's know exactly but won't share. I know because I witnessed onboard an A350 proto a while ago.

So if I will measure one type is a noisy bastard, maybe it is light & efficient because of it. But still a noisy bastard for me :wink2:

zeke · Mon Jul 02, 2018 1:49 pm

masi1157 wrote:
That is not the point! You made a completely wrong calculation that turned a factor 4 of something into a 0.6 dB difference. That is complete nonsense, and you seem still not to understand why. Therefore I will ignore the rest of your post, it is based on wrong assumptions. And that has nothing to do with me being a german engineer. You should better refrain from comments like that.

Gruß, masi1157

Ha, again because you have always done something one way, than any other way is wrong !!!!

55=Log10(1x10^55)
55.6=Log10(4x10^55)

You don’t like that because it does not have a factor or 10 or 20 infront, your engineers hat is saying that is wrong, that is wrong, that is wrong.

What would Joe Public think, if they have their radio on a volume setting of 8 and ask them to make it 4 times quieter, do they put it on a setting of 7, 6, 4, or 2 ? Joe public thinks about noise where it is generated, not where it is observed.

Forget the physics and look at the marketing, no where did they say dB, SIL etc, YOU are adding that to their comments because that is the way YOU think, look left and right.

masi1157 · Mon Jul 02, 2018 1:57 pm

Whoever in Airbus marketing came to that strange "4 times less noise", he will have based that on an input from somewhere expressed in dB or rather dB(A). And he found a difference in dB that he tried to translate into "real world numbers", but he did that very, well at least misleading. If that difference was 0.6 dB nobody with a minimum of knowledge would convert that into "4 times less noise". If it should be almost 20 dB (which it surely isn't), one could really say "perceived as 4 times less noise". If it was 12 dB (which it also won't be), it could be converted to "4 times less sound pressure", although that is rather meaningless. So I would assume he found a 6 dB difference somewhere (for sure not in the whole cabin), which in fact means "4 times less sound power energy density" and expressed that as "4 times less noise". That would still be meamingless, but the receiver will not immediately understand why. Marketing blabla.

Gruß, masi1157

masi1157 · Mon Jul 02, 2018 2:04 pm

zeke wrote:
Ha, again because you have always done something one way, than any other way is wrong !!!

This is getting ridiculous. I will not comment your posts any longer,

Gruß, masi1157

seb76 · Mon Jul 02, 2018 2:20 pm

I'll leave the A380 out here, as it is in a class of it's own, but I used to find that Airbus planes of comparable size were usually more silent than their Boeing counterparts. Especially between 737 and A320 families or 747 vs A340, the difference was so obvious. It's not so the engine noise, but especially cabin ventilation and frame (wind during cruise) make less noise in Airbus planes.

Having used the A350 and B787 however, I would say that both airplanes are pretty close (I was riding them slightly front of the wing/engine in busines class).
It seems Boeing made big progress with the 787, maybe thanks to the very smooth body (the skin hasn't all those rivets) and the no-bleed air ventilation systems.

lemontree · Mon Jul 02, 2018 2:25 pm

masi1157 wrote:
Whoever in Airbus marketing came to that strange "4 times less noise", he will have based that on an input from somewhere expressed in dB or rather dB(A). And he found a difference in dB that he tried to translate into "real world numbers", but he did that very, well at least misleading. If that difference was 0.6 dB nobody with a minimum of knowledge would convert that into "4 times less noise". If it should be almost 20 dB (which it surely isn't), one could really say "perceived as 4 times less noise". If it was 12 dB (which it also won't be), it could be converted to "4 times less sound pressure", although that is rather meaningless. So I would assume he found a 6 dB difference somewhere (for sure not in the whole cabin), which in fact means "4 times less sound power energy density" and expressed that as "4 times less noise". That would still be meamingless, but the receiver will not immediately understand why. Marketing blabla

This exactly what I think, too. I feel sorry for you, masi1157, You know a lot about this subject, but you seem to be very alone :-)

zeke · Mon Jul 02, 2018 2:52 pm

masi1157 wrote:
Whoever in Airbus marketing came to that strange "4 times less noise", he will have based that on an input from somewhere expressed in dB or rather dB(A). And he found a difference in dB that he tried to translate into "real world numbers", but he did that very, well at least misleading. If that difference was 0.6 dB nobody with a minimum of knowledge would convert that into "4 times less noise". If it should be almost 20 dB (which it surely isn't), one could really say "perceived as 4 times less noise". If it was 12 dB (which it also won't be), it could be converted to "4 times less sound pressure", although that is rather meaningless. So I would assume he found a 6 dB difference somewhere (for sure not in the whole cabin), which in fact means "4 times less sound power energy density" and expressed that as "4 times less noise". That would still be meamingless, but the receiver will not immediately understand why. Marketing blabla.

Gruß, masi1157

Finally some flexibility and clarity. Totally agree.

masi1157 wrote:
This is getting ridiculous. I will not comment your posts any longer

If it was not for me poking fun at this I don’t think you would have changed your mind and became flexible to the idea that saying up to 4 times quieter does not have engineering units.

oslmgm · Mon Jul 02, 2018 3:54 pm

zeke wrote:
If it was not for me (...)

If ignorance is what makes you happy, then good for you.
:roll:

masi1157 · Mon Jul 02, 2018 4:26 pm

The TO spoke of 6 dB less noise, the Airbus marketing document says "4 times less noise", so where is the link? Or will we still have to search for the original "6 dB statement" directly from Airbus?

Gruß, masi1157

Heinkel · Mon Jul 02, 2018 4:51 pm

PlymSpotter wrote:
To take a slightly different view on this thread, I live close to LGW and spend a lot more time under these aircraft than I do in them. The A359 appears consistently quieter than the 787-8/-9 when overflying on departure.

EASA offer a series of certification data sheets on the noise for approach, lateral and flyover which offer good insight, for example:

A350-941 - 86.3dB flyover EPNL (@ 277,000kg with Trent XWB-84)
A350-1041 - 88.3db flyover EPNL (@ 308,000kg with Trent XWB-97)

B787-8 - 88.3dB flyover EPNL (@ 227,930kg with GEnx-1B64/P1G01)
B787-8 - 87.7dB flyover EPNL (@ 227,930kg with Trent 1000-A/01)
B787-9 - 91.1dB flyover EPNL (@ 249,475kg with GEnx-1B67/P2G01)
B787-9 - 89.6dB flyover EPNL (@ 254,011kg with Trent 1000-D2)

The differences in the noise levels shown above are so small, that an untrained obersever won't hear the difference. Normal people don't hear a difference of 3 dB (dB(A)?)
The difference can be measured but it is hardly audible.

Planeflyer · Mon Jul 02, 2018 5:01 pm

No question 380 is the quietest but the 787 is OK and I do feel a bit less jet lag. I was looking for ward to flying the 350 until I read the thread about the risks associated with bled air. Do any frequent flyers here worry about the long term impacts associated with this?

trpmb6 · Mon Jul 02, 2018 5:08 pm

On the topic of the A380, where in the aircraft are people giving their anecdotal evidence for it's quietness? Upper deck? Lower Deck? what kind of configuration? cattle car config? Emirates' luxury config?

It's already been discussed that all these configurations have a huge impact.

Honestly this whole discussion really just needs to die. A & B use noise levels as a way to influence passenger opinions but most users on this forum have the background necessary to see through this. There are too many variables to pin down the different noise metrics to say which aircraft are superior.

The one thing we can at least all agree upon is that SPL is dropping with each new generation of aircraft. That is for the betterment of all of us.

Should really leave it at that and let this thread die once and for all.

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