It's far from scientific, but still, I'm impressed with how quiet the PW GTF engines are: YouTube: Airbus A320 VS Airbus A320neo - Takeoff Sound

It seems the two a/c are taken from the same vantage point using the same equipment.

As the thrust levers are pushed forward to increase engine thrust, instead of the high pitched whine, it sounds like a low pitched wind howling between two buildings.

At top of climb when autothrust transitions from THR CLB to ALT CRZ thrust, it sounds like the engines are coming back to flight idle.

It's pretty quiet.
Inside the flight deck sounds like an md-80 flight deck all you hear is wind noise, the engine noise is almost imperceptible.

Revelation wrote:

It's far from scientific, but still, I'm impressed with how quiet the PW GTF engines are: YouTube: Airbus A320 VS Airbus A320neo - Takeoff Sound

It seems the two a/c are taken from the same vantage point using the same equipment.

Gearbox permits lower tip Mach numbers on the fan so less shock noise, lower FPR produces less jet noise from the bypass, and smaller core mass flow produces less jet noise from the core.

Thanks for the two posts, they are very enlightening.

It makes one wonder how long CFM can avoid doing a GTF.

I listened to a few different YouTube vids of the LEAP and although none had as direct a comparison as the one in #1, it seems clear to me it isn't as quiet, presumably for the reasons in #3 above.

Interestingly enough, GE bought PW's partner for the gearbox ( ref: viewtopic.php?t=549749 )

akiss20 wrote:

Gearbox permits lower tip Mach numbers on the fan so less shock noise, lower FPR produces less jet noise from the bypass, and smaller core mass flow produces less jet noise from the core.

Just to clarify lower jet noise from the exit is due less speed of exiting mass of air which causes less shearing effect with the ambient air which ultimately reduces the total noise from the engines..

StereoTechque wrote:

akiss20 wrote:

Gearbox permits lower tip Mach numbers on the fan so less shock noise, lower FPR produces less jet noise from the bypass, and smaller core mass flow produces less jet noise from the core.

Just to clarify lower jet noise from the exit is due less speed of exiting mass of air which causes less shearing effect with the ambient air which ultimately reduces the total noise from the engines..

Right but what is driving that lower bypass exit velocity is the lower FPR.

Absolutely right sir..

Just flew a brand spanking new 320Neo and I liked how quiet it was. I noticed the pitch was a little sensitive on takeoff but that has nothing to do with the engine. Also was warned by the captain that if you pull the thrust to idle around 30' like you do in the Ceo it will drop out of the sky. I left it in the detent a little longer to let it do what it needed and managed a really nice landing the first time instead of plunking it on. Next time I fly one I'm gonna do the landing with auto thrust off and see how different that is. It sips fuel so I hope they get the bugs worked out of it.

Glad someone brought up this topic. I've been meaning to ask myself: Is the Buzzsaw noise completely absent on the 320NEO?

rjsampson wrote:

Glad someone brought up this topic. I've been meaning to ask myself: Is the Buzzsaw noise completely absent on the 320NEO?

Yes almost... The buzz saw is mostly prominent on the RR's.. IAE mostly was RR..

Woodreau wrote:

At top of climb when autothrust transitions from THR CLB to ALT CRZ thrust, it sounds like the engines are coming back to flight idle.

It's pretty quiet.
Inside the flight deck sounds like an md-80 flight deck all you hear is wind noise, the engine noise is almost imperceptible.

I'll nitpick here. At top of climb the autothrust goes from THR CLB to MACH (or SPEED). ALT CRZ is an autopilot vertical mode, not an autothrust mode.

Also to be fair, we can't really hear the engines while in the cruise on the 330 flight deck either.

StereoTechque wrote:

Yes almost... The buzz saw is mostly prominent on the RR's.. IAE mostly was RR..

Buzzsaw is prominent on most turbofans in specific sections of the cabin. So the GTF does have the saw? Presumably then, the tips are going supersonic and, if so, why would the saw noise be any less quiet? Mach 1 is Mach 1, after all. New noise dampening technology in the liner?

rjsampson wrote:

Buzzsaw is prominent on most turbofans in specific sections of the cabin. So the GTF does have the saw? Presumably then, the tips are going supersonic and, if so, why would the saw noise be any less quiet? Mach 1 is Mach 1, after all. New noise dampening technology in the liner?

The GTF fan is designed to rotate at a lower rpm then conventional jet engines.
Fan blade tips reaching sonic does not mean they have to create Buzzsaw effect. They might be going sonic at a higher rpm, but I'm yet to hear the saw noise from a GTF. Noise from an engine depends on lot of factors namely type of duct, accoustic liners and materials, rpm etc..

Starlionblue wrote:

I'll nitpick here. At top of climb the autothrust goes from THR CLB to MACH (or SPEED). ALT CRZ is an autopilot vertical mode, not an autothrust mode.

Also to be fair, we can't really hear the engines while in the cruise on the 330 flight deck either.

Yes I stand corrected. Autothrust transitions to MACH.

In the conventional 320 you can still hear the engines in cruise at cruise thrust but with the 320 NEOs after you get above around 15-18000ft the engines become imperceptible in the flight deck in climb thrust. When the aircraft levels off you get a little apprehension as you expect to hear the engines but don't. As the engines settle into cruise thrust settings the engines feel like they have been retarded to flight idle but they're obviously not. When you glance at the engine fuel burn numbers and they just don't seem right. They're a bit lower than you expect - again from flying the conventional 320.

It will take a little adjustment to get used to the new normal with the 320 NEO

But otherwise it flies just the same. You have to remember to turn on continuous ignition when you turn on engine anti ice. But it's just another airplane with a different engine.

At most urban airports you will be pressed to hear a GTF NEO over the city sounds. In DUS it was practically not noticeable.

rjsampson wrote:

StereoTechque wrote:

Yes almost... The buzz saw is mostly prominent on the RR's.. IAE mostly was RR..

Buzzsaw is prominent on most turbofans in specific sections of the cabin. So the GTF does have the saw? Presumably then, the tips are going supersonic and, if so, why would the saw noise be any less quiet? Mach 1 is Mach 1, after all. New noise dampening technology in the liner?

(please correct me if I'm way out on this as its been a few years since I did rotating sources of noise at university)

Soooooooo.............. The buzz saw is from the tips of the blades breaking the sound barrier, as you say, but you only hear a sonic boom if the component of travel towards you is over mach 1. If an aircraft were to do a circuit of you at mach 1.5 where you were in the middle of it then you would not hear the boom (no component of velocity towards you). Likewise with a rotating engine if we simplified the scenario and there was no noise reflecting from the other parts of the engine and you only heard the fan directly and you were stood directly in front of it then in that plane of reference there is no component moving towards the observer at over M1, so no sonic booms. As you move away from the centre line of the engine the component of velocity directly towards the observer increases and if the fan tips are going supersonic then at some point when you move to a sufficient angle from the centre line you will hear the booms. As the fan tip speed slows the greater that angle has to be and so a smaller area where the "booms" will be percieved. If there is less areas for the booms to be perceived then there will be less noise even taking into account the surfaces that will undoubtedly transmit those noises.

Did any of that make sense? If only I had time to draw a picture then it would be much easier.

Fred

StereoTechque wrote:

rjsampson wrote:

Glad someone brought up this topic. I've been meaning to ask myself: Is the Buzzsaw noise completely absent on the 320NEO?

Yes almost... The buzz saw is mostly prominent on the RR's.. IAE mostly was RR..

Buzzsaw sound is prominent on most turbofans to this date regardless of manufacturer. The CFM56 is one of the loudest and most noticeable buzzers along with the IAE V2500 which actually mostly wasn't RR's work.

The fans will buzz at higher thrust settings and as the engines slow down the intensity decreases until the point where it would seem to stop buzzing on a video for example, but in reality I have noticed that there is a hum below that that continues down for a bit before totally fading away. For example, the CFM56-5A will buzz quite loudly at its well known pitch and as the engine speed slows down the buzz fades away and then stops buzzing all together at around the frequency a PW2000 would normally buzz at. This is where the buzzless hum is. It continues down to about the frequency a CF6 makes at TOGA and below that fades away all together. That must be the point where the entire fan goes subsonic. If you watch a high quality video of an A320neo, with the PW1000G you will hear not a buzz, but a subdued deep hum when on climb power given you have good audio equipment. This may mean that part of the fan is exceeding Mach 1, but not by the margin older turbofans do. This is similar to how the buzz of a turbofan fades away as the plane climbs in altitude. The actual speed of Mach 1 increases, yet the fan does not increase speed so it's Mach goes down and so does the intensity of sonic boom.

The CFM LEAP seems to come closer to buzzing, but a very weak buzz. I have heard some videos of the -1A and -1B slightly buzzing, but without much intensity.
You can hear a slight buzz on climb thrust at about the frequency an engine such as the CF6 would buzz at on the -1A or PW2000/RB211 would buzz at on the -1B , of course with much less intensity:

https://youtu.be/3GAJR79ndZ4?t=245
Or here:
https://youtu.be/7lOVBhEReOk?t=16
Or here:
https://youtu.be/XLRSUO2dRyY?t=37

767333ER wrote:

. This may mean that part of the fan is exceeding Mach 1, but not by the margin older turbofans do. This is similar to how the buzz of a turbofan fades away as the plane climbs in altitude. The actual speed of Mach 1 increases, yet the fan does not increase speed so it's Mach goes down and so does the intensity of sonic boom.

speed of sound decreases with altitude, under ISA condition it is about 342ms^-1 at sea level (15C) and 295ms^-1 by the time you are at the tropopause (-56C). Of course that's all ideal scenarios but the General trend doesn't change much.

Fred

Does the LH bird climb much faster than the Vueling one ? ... or is that just a trick on the eye?

WIederling wrote:

Does the LH bird climb much faster than the Vueling one ? ... or is that just a trick on the eye?

It also looks like it accelerates much faster… Maybe it's only due to the load, however…

767333ER wrote:

https://youtu.be/3GAJR79ndZ4?t=245
Or here:
https://youtu.be/7lOVBhEReOk?t=16
Or here:
https://youtu.be/XLRSUO2dRyY?t=37

I didn't hear any buzzing on the first two videos (but the second video was obstructed by music). I did hear a little buzz on the third video. Which by the way, was really cool.

Unless I'm missing something... the same "revolutionary" thing was developed, and put into production (with far less fanfare) by the piston-banger manufacturer, Lycoming, in their ALF 502 engine. I only got 3 right-seat hours on the 604, but I knew it buzzed. And as a passenger travelling Europe, the same engine buzzed on the Avro's.

Does PW has some sort of "secret sauce" on their gearbox that Lycoming didn't have? Or is this essentially marketing? If so, it really makes me wonder why Lycoming's idea failed. I guess it was initially their limited market: Their engine's only applications, as far as I know, were on variants of the 146s, and the Bombardier Challenger 604.

Yet, no company put another GTF into production (I don't know) from 30 years ago, until now, when Pratt pushed out their latest product. I've been scratching my head over that for years.

rjsampson wrote:

Unless I'm missing something... the same "revolutionary" thing was developed, and put into production (with far less fanfare) by the piston-banger manufacturer, Lycoming, in their ALF 502 engine.

Yet, no company put another GTF into production (I don't know) from 30 years ago, until now, when Pratt pushed out their latest product. I've been scratching my head over that for years.

They did not fail.
What PW achieved was massive upward scaling.
( and problems go up with the square of power.)

tb727 wrote:

. Also was warned by the captain that if you pull the thrust to idle around 30' like you do in the Ceo it will drop out of the sky.

Why is that different in the NEO than it was before?

I thought Airbus flight envelope was designed in a way to prevent such possibilities, what do I miss here?

Eyad89 wrote:

tb727 wrote:

. Also was warned by the captain that if you pull the thrust to idle around 30' like you do in the Ceo it will drop out of the sky.

Why is that different in the NEO than it was before?

I thought Airbus flight envelope was designed in a way to prevent such possibilities, what do I miss here?

I think what tb727 meant was that retarding the thrust levers during the flare must be done later than on the CEO or you'll find yourself making a rather more firm touchdown than what you intended.

Starlionblue wrote:

Eyad89 wrote:

tb727 wrote:

. Also was warned by the captain that if you pull the thrust to idle around 30' like you do in the Ceo it will drop out of the sky.

Why is that different in the NEO than it was before?

I thought Airbus flight envelope was designed in a way to prevent such possibilities, what do I miss here?

I think what tb727 meant was that retarding the thrust levers during the flare must be done later than on the CEO or you'll find yourself making a rather more firm touchdown than what you intended.

Exactly. It doesn't literally fall out of the sky, it just feels like it!

Slightly off topic, but has anyone noticed a Sweet low-pitched whistling sound(couldnt think of any better terminology) from the inlet of the GTF once stabilised. I have the opportunity of standing around it during start-up...

rjsampson wrote:

Unless I'm missing something... the same "revolutionary" thing was developed, and put into production (with far less fanfare) by the piston-banger manufacturer, Lycoming, in their ALF 502 engine. I only got 3 right-seat hours on the 604, but I knew it buzzed. And as a passenger travelling Europe, the same engine buzzed on the Avro's.

Does PW has some sort of "secret sauce" on their gearbox that Lycoming didn't have? Or is this essentially marketing? If so, it really makes me wonder why Lycoming's idea failed. I guess it was initially their limited market: Their engine's only applications, as far as I know, were on variants of the 146s, and the Bombardier Challenger 604.

Yet, no company put another GTF into production (I don't know) from 30 years ago, until now, when Pratt pushed out their latest product. I've been scratching my head over that for years.

First, I finally realized I should be looking at the EASA documents for certified noise:
https://www.easa.europa.eu/system/files ... ssue12.pdf

I'll take approach noise as that was the highest dB and seems to be consistently closest to the limits, highest weight in table
CFM-56-5: 95.2 db (Older fans a tiny bit louder, as high as 96.1dB).
V2500-A5: 94.4dB Note: V2500-A1 louder at 96.6 dB
LEAP-1A: 92.6dB
PW1100G: 92.2 dB


So lots of debate for a small noise difference. When I look at takeoff lateral noise, the LEAP is actually quieter than the PW1127G!

So who thinks which engine is louder is going to be dependent upon where they live (side of runway, they'll prefer the LEAP, approach path the PW1100G). Either way, a few dB might not seem like much, but it is significant for the NEO. Not as much noise reduction as I hoped, but oh well.

Look at the C-series, the CS300 has similar noise in approach, but less takeoff:
https://www.easa.europa.eu/system/files ... 11_1.0.pdf

Yes, for the CS300 86.9dB lateral, 92.4dB approach

One would expect the CS500 to be 2dB louder (rho rho, getting up there) and a CS700 another 2dB louder (getting close) with the CS900 proposed by some requiring a new wing just to keep down noise!

Lightsaber

StereoTechque wrote:

Slightly off topic, but has anyone noticed a Sweet low-pitched whistling sound(couldnt think of any better terminology) from the inlet of the GTF once stabilised. I have the opportunity of standing around it during start-up...

I believe you are referring to this sound: https://youtu.be/fuVflmVJ2Hk?t=179

It reminds me of the similar distinct howl the CF34-8 makes .

767333ER wrote:

I believe you are referring to this sound: https://youtu.be/fuVflmVJ2Hk?t=179
.

Not really audible in this video. I believe you can only hear when you are outside but at the same time very near to the aircraft..

https://youtu.be/fuVflmVJ2Hk?t=273 (time marked)

Well, that answers my question: The fan tips are clearly supersonic. There is a buzzsaw, it this video (at precisely the location from which the video was taken, where the buzzsaws are typically pronounced).

But dang -- it sure is extremely subtle. That is one quiet engine.

lightsaber wrote:

rjsampson wrote:

Unless I'm missing something... the same "revolutionary" thing was developed, and put into production (with far less fanfare) by the piston-banger manufacturer, Lycoming, in their ALF 502 engine. I only got 3 right-seat hours on the 604, but I knew it buzzed. And as a passenger travelling Europe, the same engine buzzed on the Avro's.

Does PW has some sort of "secret sauce" on their gearbox that Lycoming didn't have? Or is this essentially marketing? If so, it really makes me wonder why Lycoming's idea failed. I guess it was initially their limited market: Their engine's only applications, as far as I know, were on variants of the 146s, and the Bombardier Challenger 604.

Yet, no company put another GTF into production (I don't know) from 30 years ago, until now, when Pratt pushed out their latest product. I've been scratching my head over that for years.

First, I finally realized I should be looking at the EASA documents for certified noise:
https://www.easa.europa.eu/system/files ... ssue12.pdf

I'll take approach noise as that was the highest dB and seems to be consistently closest to the limits, highest weight in table
CFM-56-5: 95.2 db (Older fans a tiny bit louder, as high as 96.1dB).
V2500-A5: 94.4dB Note: V2500-A1 louder at 96.6 dB
LEAP-1A: 92.6dB
PW1100G: 92.2 dB


So lots of debate for a small noise difference. When I look at takeoff lateral noise, the LEAP is actually quieter than the PW1127G!

So who thinks which engine is louder is going to be dependent upon where they live (side of runway, they'll prefer the LEAP, approach path the PW1100G). Either way, a few dB might not seem like much, but it is significant for the NEO. Not as much noise reduction as I hoped, but oh well.

Look at the C-series, the CS300 has similar noise in approach, but less takeoff:
https://www.easa.europa.eu/system/files ... 11_1.0.pdf

Yes, for the CS300 86.9dB lateral, 92.4dB approach

One would expect the CS500 to be 2dB louder (rho rho, getting up there) and a CS700 another 2dB louder (getting close) with the CS900 proposed by some requiring a new wing just to keep down noise!

Lightsaber

Considering how close the measuring point for the approach value is to the threshold, it is mostly aerodynamic noise, with very little engine input in comparison. The lateral and flyover values are much more influenced by the engine. And there we are looking at close to 6db improvement, which means people will consider the plane half as loud.

So much of the noise onboard is the air circulation and fans inside the aircraft that seem to be blocking out the sound of the engine creating "white noise".
Frankly, I would rather hear the buzz saw than "white noise". Surprising that they have not done more with the "white noise" on these new planes. They are focusing on the wrong thing in my opinion -- their passengers. Listen to the last video posted and you can hear what I mean.

The CFM LEAP buzzes when higher thrust is applied. You can hear it quite clearly in this video:

https://youtu.be/A2Roxy_6faY?t=692

I just flew the A320 NEO with the Leap Engines for the first time today (Pegasus Airlines), and I have to say it is by far the quietest plane I have ever flown, including upper deck A380, 77W, etc. The only plane I want to check it with is the 787, which I havent managed to fly yet!

For a small plane though, is amazing. I was sitting in 24F, which is right behind the wing so should be one of the loudest seats on the plane. Forget it! You barely hear the engines start up, then when you taxi you barely hear anything. Then when you take off again, it feels like taxiing noise on the normal A320. Really amazing. I noticed a sensitive pitch control upon take off on the plane. Even when climbing, you hear the packs more than the engines. Cruise and descent were crazy quiet, on approach you could barely hear the throttles moving according to the demand on short finals! Lol now I'm at SAW waiting for another plane to take me to my destination, and it will be a 738, so basically much, much louder!

Another thing I found funny on the A320NEO is the fact that on the no seatbelt sign display, you don't have a no smoking sign, you have a laptops/tablets/phones off sign! The no smoking sign is a permanent sticker to the next of it. I guess all planes should be like that, as I did not listen to crew to stop using my laptop, but waited for the light to go on about 60 seconds before touchdown before stowing my laptop!