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What Makes Engine Sounds Unique?  
User currently offlinePilotboi From United States of America, joined Sep 2007, 2366 posts, RR: 9
Posted (5 years 9 months 1 week 6 days 1 hour ago) and read 8096 times:

I'm very well aware of the fact that different manufacturer's engines sound different. But I have two questions really...the first is simple, how can you distinguish each type by the sound? In other words, how can you tell them apart? The second is a little more tricky (for some) and really is what I'm interesting in finding out with this thread...what makes each one unique? In other words, why do they sound the way they do?

31 replies: All unread, showing first 25:
 
User currently offlineRutankrd From United Kingdom, joined Sep 2003, 3038 posts, RR: 8
Reply 1, posted (5 years 9 months 1 week 6 days ago) and read 8046 times:

Simply sonics and acoustic properties

Each engine design differs in materials used size/shape number of moving parts amount of gas forced through and therefore differing resonances.

The external baffles and cowlings of jets also effect the noise.

Props having no baffles produce that deep bass through vibration as they cut through the air and in the case of the helicopter blade these may be running close to the sound barrier at the tip resulting in mini sonic booms


User currently offlineCanadianNorth From Canada, joined Aug 2002, 3395 posts, RR: 9
Reply 2, posted (5 years 9 months 1 week 6 days ago) and read 8046 times:

Where I come from it's pretty easy, since the airliners up there are so vastly different. However, here are a few I'm generally able to call:
-JT8D powered aircraft have what I would call a thundering sound, I believe it's mainly due to simply being a relatively low bypass engine.
-RR Darts to me are instantly recognizable by their screaming, especially at low power settings, and I've been told it's the gearbox that does the screaming.


CanadianNorth



What could possibly go wrong?
User currently offlineJQFlightie From Australia, joined Mar 2009, 1007 posts, RR: 1
Reply 3, posted (5 years 9 months 1 week 6 days ago) and read 8019 times:

well i would love to meet the creator of the IAE engines on our A320's!! they are sooooooooo noise on take off! as im up the front of the aircraft alot as R1 Cabin Crew, but then if i am PAX'ing sitting at the Over-Wing exits it is extreemly quite, and then if i am working down the back of the aircraft its another sound!


Next Trip: PER-DPS-KUL-BKK-HKT-CNX-BKK-SIN-PER
User currently offlineFatmirJusufi From Albania, joined Jan 2009, 2441 posts, RR: 7
Reply 4, posted (5 years 9 months 1 week 6 days ago) and read 8005 times:



Quoting JQFlightie (Reply 4):
well i would love to meet the creator of the IAE engines on our A320's!!

Haha! Just my thoughts...

Check it out
http://www.youtube.com/watch?v=P1SjtT6GUdI

Fatmir



DO FLIGHTS. NOT FIGHTS.
User currently offlineJQFlightie From Australia, joined Mar 2009, 1007 posts, RR: 1
Reply 5, posted (5 years 9 months 1 week 6 days ago) and read 7985 times:



Quoting FatmirJusufi (Reply 5):
Haha! Just my thoughts...

Check it out
http://www.youtube.com/watch?v=P1SjtT6GUdI

Fatmir

OMG lol that is the exact sound from the front of the cabin a loud wining sound....thanks for that.....
but to make it worse i was on a BA A320 last november and their A320's are extreemly old bird... and alot louder!



Next Trip: PER-DPS-KUL-BKK-HKT-CNX-BKK-SIN-PER
User currently offlineComorin From United States of America, joined May 2005, 4903 posts, RR: 16
Reply 6, posted (5 years 9 months 1 week 5 days 23 hours ago) and read 7941 times:

The GE90's are famous for their 'mooing' sound on engine start - quite a few videos on Youtube! I'll post one later when I get back from work.

User currently offlineKhobar From United States of America, joined Mar 2006, 2379 posts, RR: 4
Reply 7, posted (5 years 9 months 1 week 5 days 23 hours ago) and read 7884 times:

Interesting question.

We have a good mix of 737's and comparable Airbii fly over on approach, and the general difference between the Boeing's and Airbii is very apparent. 737 on approach has more of a roar while the Airbii generally have more of a whine/scream.

I haven't paid attention to the differences between Airbii with differing engine types however.


User currently offlineSeaBosDca From United States of America, joined Sep 2007, 5824 posts, RR: 6
Reply 8, posted (5 years 9 months 1 week 5 days 23 hours ago) and read 7864 times:

Love the CFM56-5/7 buzz saw sound on takeoff... immediately recognizable because the pitch and timbre are different from other high-bypass engines.

PW2000-powered 757s are cool too, because the pitch is lower and they sound relaxed even at full power.


User currently offlineComorin From United States of America, joined May 2005, 4903 posts, RR: 16
Reply 9, posted (5 years 9 months 1 week 5 days 22 hours ago) and read 7806 times:

So what are the sources of these sounds?

My humble guesses:

1. Subsonic airfoil sounds from the fan (hairdryer, vacuum cleaner).
2. Compressor and geartooth whine proportional to rotation speed.
3. Supersonic roar of air exiting exhaust nozzles.

I am not sure if there are any cavitation effects, and I am not sure how turbulent flow generates noise.

Engineers, please correct !


User currently offlineCFMTurboFan From Canada, joined May 2007, 41 posts, RR: 0
Reply 10, posted (5 years 9 months 1 week 5 days 22 hours ago) and read 7787 times:

The RB211 D4s BA used to run on the 747-200 had a very distinct growling sound they made during start up. This was caused by the fan blade clapper faces. As the engine accelerates, the fan blade centrifuge out into the dovetail slots of the fan hub, which reduces the amount of growling (but does not eliminate it).

The RB211 G/H engine BA has fitted on the 747-400 & 767 fleets did not make this noise as they have wide chord fan blades fitted. These engines made more of a whoosh noise on start up and engine running.

Generally any high bypass engine that has clapper faces midway up the fan blade will made some sort of growling during normal engine running. I watched a US Navy Viking two years ago at an air display, which made these distinct sounds. I was explaining this to some of my work colleagues who were wondering what the noise was.

Hope this answers some of the questions.

CFM Turbo Fan


User currently offlineKtachiya From Japan, joined Sep 2004, 1803 posts, RR: 2
Reply 11, posted (5 years 9 months 1 week 5 days 22 hours ago) and read 7782 times:

Very interesting thread. Although not right the whole time, this is a technique that I've developed over the years to distinguish the three engine makers at least in Japanese heavies (and some RR powered engines). I can usually guess when the aircraft starts rolling and the pilot applies full thrust upon takeoff.

RR - Sounds very unique to me and actually checked it out on a few CX B744 takeoff videos but it makes an extremely low rumbling sound when applied to full power. It also continues this sound even during its climb.

PW - I see the most often when I am spotting at ITM because it is on the T7's that NH/JL has. It sounds like a sportscar when it goes right past me.

CF - This sounds the most normal and does not have any rumbling sounds associated with it based on what I have seen so far during the whole takeoff roll phase. It also tends to make a high pitched noise? from what I've noticed.

Of course this is just IMHO and many people have different perspectives. Also, this can only be said when you are viewing the takeoff aircraft from 90 degrees (so when it goes from your left to right or vice versa) in airports such as ITM or NGO. It can't really be used elsewhere but I would love to hear what others say.

Also while we are on this topic, can I also ask about reverse thrust? I don't notice any differences on reverse thrust but is there a way that somebody can tell the difference?



Flown on: DC-10-30, B747-200B, B747-300, B747-300SR, B747-400, B747-400D, B767-300, B777-200, B777-200ER, B777-300
User currently offlineJBo From Sweden, joined Jan 2005, 2379 posts, RR: 0
Reply 12, posted (5 years 9 months 1 week 5 days 22 hours ago) and read 7760 times:



Quoting SeaBosDca (Reply 9):
Love the CFM56-5/7 buzz saw sound on takeoff... immediately recognizable because the pitch and timbre are different from other high-bypass engines.

No doubt inherited from the TF-39 ... http://www.youtube.com/watch?v=uJvI9bdteko Big grin



I'd take the awe of understanding over the awe of ignorance any day.
User currently offlineAaron747 From Japan, joined Aug 2003, 8275 posts, RR: 26
Reply 13, posted (5 years 9 months 1 week 5 days 21 hours ago) and read 7753 times:

I still have no idea what makes them sound so unique, but I've always been in love with the PW4000 vacuum cleaners on the 777, especially the tinny hum of the PW4090:

outside (my video)

http://www.youtube.com/watch?v=UuLMJXemd-Y

inside

http://www.youtube.com/watch?v=phogRUBSP5U

Listen to the latter around 1:05...absolute music to my ears. To be fair though, all 777 engine options sound incredible on takeoff.



If you need someone to blame / throw a rock in the air / you'll hit someone guilty
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 14, posted (5 years 9 months 1 week 5 days 21 hours ago) and read 7750 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting Khobar (Reply 7):
the general difference between the Boeing's and Airbii is very apparent. 737 on approach has more of a roar while the Airbii generally have more of a whine/scream.

NWA A320s regularly pass over my house on approach to MSN. They usually pass overhead at around 3,000 or 4,000 AGL with the engines at (or near) flight idle, and those engines make a very distinctive sound as they pass by.

I think it's a combination of the engine itself and the doppler effect as the aircraft passes overhead. The frequency/pitch change that occurs is very strange. None of the other aircraft (ERJs, CRJs, DC-9s) sound anything like it.

2H4



Intentionally Left Blank
User currently offlineKeta From Germany, joined Mar 2005, 448 posts, RR: 0
Reply 15, posted (5 years 9 months 1 week 5 days 20 hours ago) and read 7713 times:



Quoting Comorin (Reply 9):
Supersonic roar of air exiting exhaust nozzles

In airliner's turbofans (you're perhaps referring to fighter aircraft?) exhaust velocity is subsonic.
Disclaimer: I'm speaking out of memory and thought, will have to check that  Smile



Where there's a will, there's a way
User currently offlineBMI727 From United States of America, joined Feb 2009, 15828 posts, RR: 27
Reply 16, posted (5 years 9 months 1 week 5 days 15 hours ago) and read 7576 times:

Generally, the roaring sound is due to the exhaust. This sound will be louder on lower bypass engines. (MD-80s and military aircraft for example) The buzzsaw sound is from the fan blades.
As was stated before, the nacelle of the engine has an effect on the sound so the same engine on two different types may sound different.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 17, posted (5 years 9 months 1 week 5 days 9 hours ago) and read 7450 times:

Quoting Pilotboi (Thread starter):
The second is a little more tricky (for some) and really is what I'm interesting in finding out with this thread...what makes each one unique?

A whole bunch of things. Aerodynamics (especially the fan blades) are a biggie. Nacelle design is a contributor (especially the acoustic treatments), and engine architecture (where the exhaust goes and how it's mixed with the fan stream, and how many spools).

There are some very strange engine architectures out there. I'm sure this one has some noise effects due to the very odd way of mixing the exhaust and the fan flows:
http://www.flightglobal.com/airspace...ays/garrett-atf3-cutaway-5603.aspx

Quoting Comorin (Reply 9):
1. Subsonic airfoil sounds from the fan (hairdryer, vacuum cleaner).

Fans are usually locally supersonic at takeoff, actually.

Quoting Comorin (Reply 9):
2. Compressor and geartooth whine proportional to rotation speed.

I'm not sure you can hear the gearbox over the general engine noise...that sounds to me like a gearbox in trouble.

Quoting Comorin (Reply 9):
3. Supersonic roar of air exiting exhaust nozzles.

Only on supersonic aircraft:

Quoting Keta (Reply 15):
In airliner's turbofans (you're perhaps referring to fighter aircraft?) exhaust velocity is subsonic.
Disclaimer: I'm speaking out of memory and thought, will have to check that

You don't want supersonic exhaust on a subsonic aircraft. It lowers propulsion efficiency without any counterveiling benefit (and it's loud).

You will be very close to sonic at the exit of many turbofans, but the nacelle design generally wouldn't even allow you to get a supersonic exhaust flow.

Quoting Comorin (Reply 9):
I am not sure if there are any cavitation effects, and I am not sure how turbulent flow generates noise.

You can't actually cavitate a jet engine, because cavitation is a phase change brought about by low pressure. Since the working fluid is already a gas, it's got nowhere to go. You may be thinking of separation, which is qualitatively similar to ventilation on liquid-propellors, but somewhat different physically.

Turbulent flow generates noise because the turbulence is driven by steep local pressure gradients, which radiate pressure waves away. You hear the pressure waves as sound.

Tom.

[Edited 2009-03-11 21:43:45]

User currently offlineOsiris30 From Barbados, joined Sep 2006, 3192 posts, RR: 25
Reply 18, posted (5 years 9 months 1 week 5 days 8 hours ago) and read 7435 times:



Quoting Tdscanuck (Reply 17):
There are some very strange engine architectures out there. I'm sure this one has some noise effects due to the very odd way of mixing the exhaust and the fan flows:
http://www.flightglobal.com/airspace....aspx

I seem to recall we had someone on this forum who may have some first hand experience with that beasty.. Dougloid I believe. He may be able to confirm that for you  Smile



I don't care what you think of my opinion. It's my opinion, so have a nice day :)
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25978 posts, RR: 22
Reply 19, posted (5 years 9 months 1 week 5 days 7 hours ago) and read 7416 times:



Quoting CanadianNorth (Reply 2):
RR Darts to me are instantly recognizable by their screaming, especially at low power settings, and I've been told it's the gearbox that does the screaming.

Agree, the R-R Dart has one of the most recognizable engine sounds of any aircraft. Strangely, the high-pitched whine wasn't noticeable inside the aircraft, at least on Viscounts and F27s.

Good example of the Dart scream on an F27 on these old videos at AEP, the domestic/regional airport in Buenos Aires.
http://www.youtube.com/watch?v=tfbO50S-qmo
http://www.youtube.com/watch?v=rYPIYFJ8d6A&
http://www.youtube.com/watch?v=Vr63k4ZoT8M


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1658 posts, RR: 1
Reply 20, posted (5 years 9 months 1 week 5 days 6 hours ago) and read 7390 times:

Sound? You want sound?

There is nothing on Earth like the Rolls Royce Merlin engine; there are many examples on YouTube. Just look up P-51 or Spitfire and enjoy.


User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 21, posted (5 years 9 months 1 week 4 days 22 hours ago) and read 7334 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting ThirtyEcho (Reply 20):
There is nothing on Earth like the Rolls Royce Merlin engine; there are many examples on YouTube. Just look up P-51 or Spitfire and enjoy.

Better yet, come to Oshkosh this July and bask in the glory that is multiple P-51s advancing throttles for takeoff simultaneously.....from about 100 feet away.  cloudnine 

2H4



Intentionally Left Blank
User currently offlinePilotboi From United States of America, joined Sep 2007, 2366 posts, RR: 9
Reply 22, posted (5 years 9 months 1 week 4 days 22 hours ago) and read 7331 times:



Quoting 2H4 (Reply 21):
Better yet, come to Oshkosh this July and bask in the glory that is multiple P-51s advancing throttles for takeoff simultaneously.....from about 100 feet away.

Was there, myself, last year. I preferred the thunder of the Raptor doing a high speed pass. But to each their own.


User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 23, posted (5 years 9 months 1 week 4 days 21 hours ago) and read 7323 times:



Quoting Pilotboi (Thread starter):
the first is simple, how can you distinguish each type by the sound

Its all about practice.....Hearing them often one can tell the difference.Its like watching aircraft & knowing the type over time.
regds
MEL.



Think of the brighter side!
User currently offlineKL671 From Canada, joined Jul 2005, 141 posts, RR: 0
Reply 24, posted (5 years 9 months 1 week 2 days 15 hours ago) and read 7004 times:



Quoting Pilotboi (Thread starter):
The second is a little more tricky (for some) and really is what I'm interesting in finding out with this thread...what makes each one unique? In other words, why do they sound the way they do?

Noise from a turbine engine is created from both the inlet and the exhaust.

The inlet noise from the compressor is at higher frequencies. When a rotating compressor blade passes a stationary object such as a vane, it creates a pressure fluctuation. This pressure fluctuation creates noise at a frequency which is a function of the rotational speed of the rotor multiplied by the number of blades. Turbines have many stages with different numbers of blades and vanes and so generate many different frequencies.

The exhaust noise is much lower in frequency and is caused by the combustion process.

Different manufacturers use different shaft rotational speeds, number of blades, number of vanes and cumbuster configurations. Thus each engine model produces a unique sound.

Hope this helps.


25 Keta : In addition to what KL671 and others overall correctly stated, I will go deeper into how engines make noise. Primarily, the noise is generated by the
26 Access-Air : Well to expound upon these two engine types, the JT8D in the earlier version (lower power) that have a more, as I call it, Jetty sounds like on the D
27 Aaron747 : Excellent detail and technical analysis. Thanks! So are we to assume then that the PW4090 "woo woo woos" are by design?
28 Tdscanuck : The physics are similar, but where the "fluted" (undulating) nozzles are usually seen between the core and fan streams, the 787 appears to have a con
29 FlyASAGuy2005 : Surprisingly, no one has mentioned the engines on the CRJ! They have a particular high pitched"scream. Very prevelent on take-off and when the a/c is
30 LASOctoberB6 : I've memorized the common types out at McCarran. I just got used to it over the years.. I asked about that particular thing in a thread around a year
31 Keta : Yes, well, that's what I meant when I cited the B-787. The chevrons aim to reduce noise of the bypass exhaust by the same means as the fluted nozzles
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