Pilotboi From United States of America, joined Sep 2007, 2366 posts, RR: 9 Posted (6 years 11 months 6 days 22 hours ago) and read 10071 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?
Rutankrd From United Kingdom, joined Sep 2003, 3309 posts, RR: 4
Reply 1, posted (6 years 11 months 6 days 22 hours ago) and read 10021 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
CanadianNorth From Canada, joined Aug 2002, 3417 posts, RR: 7
Reply 2, posted (6 years 11 months 6 days 22 hours ago) and read 10021 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.
JQFlightie From Australia, joined Mar 2009, 1106 posts, RR: 2
Reply 3, posted (6 years 11 months 6 days 21 hours ago) and read 9994 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!
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!
Khobar From United States of America, joined Mar 2006, 2379 posts, RR: 3
Reply 7, posted (6 years 11 months 6 days 20 hours ago) and read 9859 times:
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.
CFMTurboFan From Canada, joined May 2007, 41 posts, RR: 0
Reply 10, posted (6 years 11 months 6 days 19 hours ago) and read 9762 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.
Ktachiya From Japan, joined Sep 2004, 1855 posts, RR: 1
Reply 11, posted (6 years 11 months 6 days 19 hours ago) and read 9757 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?
2H4 From United States of America, joined Oct 2004, 8957 posts, RR: 58
Reply 14, posted (6 years 11 months 6 days 18 hours ago) and read 9725 times:
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.
BMI727 From United States of America, joined Feb 2009, 16559 posts, RR: 27
Reply 16, posted (6 years 11 months 6 days 12 hours ago) and read 9551 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?
Tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 80
Reply 17, posted (6 years 11 months 6 days 6 hours ago) and read 9425 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).
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.
KL671 From Canada, joined Jul 2005, 144 posts, RR: 0
Reply 24, posted (6 years 11 months 3 days 12 hours ago) and read 8979 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.
: 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
: 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
: Excellent detail and technical analysis. Thanks! So are we to assume then that the PW4090 "woo woo woos" are by design?
: 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
: 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
: 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
: 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