A320 Noise

[Edinburgher]

I posted this elsewhere on the forum, but have not received an explanation as yet, so thought it was time to ask you who actually fly the machines. Hope this isn't in the wrong forum, but I am a newbie.

I have a wee question about engine noise on the Airbus A320 - apologies if this has been covered elsewhere. I flew back from Heathrow to Edinburgh on Monday evening with BA, on what turned out to be my first flight on an Airbus A320. All seemed very much like travelling on similar Boeing aircraft on the push-back and taxi for take-off. However, when the pilots powered up the engines for take off, what can only be described as a very loud buzzing noise could be heard behind me (I was in row 3), which I assume originated from the engines. This only seemed to disapear when we completed the climb.

I have to say, at first I thought there might be some sort of technical problem, as the noise was so prominent. However, as the climb-out progressed normally, and the cabin crew seemed totally relaxed, it was obvious this wasn't the case. Can anyone tell me if this is normal for this type of aircraft and if it is indeed a result of the engines, as I have not experienced such a phenomenon when travelling on, say a 737-300.

Oh, I should just add that apart from the initial noise, the flight and service were great.

Many thanks!

[Engine overtemp]

You will hear a loud "buzzing noise" on the A320 during the engine start sequence as the hydraulic system conducts a test on the PTU (power transfer unit - a way of utilising hydraulic fluid in a system if the related hydraulic pump fails). However this only lasts for a few seconds, are you sure it lasted as long as you say?

[longarm]

The PTU noise during start up sounds more like a dog barking. The sound mentioned sounds more like normal engine noise. Quite often this has a buzzy resonance on the A320 especially at high power.

[miss_heard]

I posted this elsewhere on the forum, but have not received an explanation as yet, so thought it was time to ask you who actually fly the machines. Hope this isn't in the wrong forum, but I am a newbie.
I have a wee question about engine noise on the Airbus A320 - apologies if this has been covered elsewhere. I flew back from Heathrow to Edinburgh on Monday evening with BA, on what turned out to be my first flight on an Airbus A320. All seemed very much like travelling on similar Boeing aircraft on the push-back and taxi for take-off. However, when the pilots powered up the engines for take off, what can only be described as a very loud buzzing noise could be heard behind me (I was in row 3), which I assume originated from the engines. This only seemed to disapear when we completed the climb.
I have to say, at first I thought there might be some sort of technical problem, as the noise was so prominent. However, as the climb-out progressed normally, and the cabin crew seemed totally relaxed, it was obvious this wasn't the case. Can anyone tell me if this is normal for this type of aircraft and if it is indeed a result of the engines, as I have not experienced such a phenomenon when travelling on, say a 737-300.
Oh, I should just add that apart from the initial noise, the flight and service were great.
Many thanks!
I believe the 'buzz saw' noise you are referring to is caused largely by the fan tips being supersonic (and the resulting noise interacting with other tonal sources in the engine). I have noticed the same thing sitting in row 1 on a BA A319 (an awful racket which dies down v slightly after take-off!)
:ok:

[Rainboe]

There are 2 reasons (that I know of) why the A320 series is known as 'the Strimmer'. This buzzing is one reason!

[Old Smokey]

I've said it before..............and I'll say it again...............

We need a dedidacted forum devoted entirely to strange Airbus noises.

Moderators please note!:ok:

Regards, :}

Old Smokey

[Mark 1]

Fan Buzz-saw noise is a well known and documented phenomenon.

It is caused by shock waves from the supersonic fan tips propagating non-linearly (i.e. speed of sound varies with shock intensity).

Small differences between blades are exaggerated by this effect and the pressure wave is 'randomized' as it emerges from the intake.
The fundamental frequency of the tone is the shaft speed not the blade passing frequency (e.g. a 4000RPM fan produces buzz tones at multiples of 67hz, whereas the fan fundamental tone would be say 2000hz with a 30 blade fan).

[TotalBeginner]

Does anybody know what that strange noise is that comes on intermittently on the ground. Sounds like an air-raid siren??? :confused:

[Edinburgher]

Many thanks to everyone who has replied to my, slightly mundane, query. So I am right in thinking that the noise is a consequence of supersonic-related resonance in the engines?

Now, I'm not sure what varient of A320 I was flying on (and consequently which engine type the aircraft had), but I understand that there is a common engine type between certain varients of A320s and 737s. If this is the case, could someone explain why I've not experienced the same noise when travelling numerously on 737s (mainly 300s). To narrow the variables down, the flight I took was with BA was from Heathrow to Edinburgh at @ 20.35 on 05/04 (hopefully this will help identify the aircraft concerned).

Many thanks for all your assistance with stemming my curiosity.

[Mark 1]

Its not a resonance. The fan is typically supersonic above about 70-80%N1.
The level of buzz-saw noise may reduce at higher fan speed due to the 'swallowing' effect of higher axial flow in the intake. It is not well attenuated by most intake acoustic treatment due to the lower frequency and hence longer wavelength.

TotalBeginner - the noise you refer to is probably combustion howl, generally only evident at very low power settings (e.g. ground idle).

[TotalBeginner]

No, this sound is only audible from outside of the aircraft, when the engines are shut down. It's very loud and only seems to last for a couple of minutes. I thought it might be the recirculation fans, but somebody suggested that it was something to do with the brakes cooling?? Not sure I understand how cooling brakes could make such a mechanical noise?????????

[AnEviltwinEr]

Does anybody know what that strange noise is that comes on intermittently on the ground. Sounds like an air-raid siren??? :confused:

What you hear in the cabin, is the apu i believe. (auxillary power unit)

[7gcbc]

I've said it before..............and I'll say it again...............
We need a dedidacted forum devoted entirely to strange Airbus noises.
Moderators please note!:ok:
Regards, :}
Old Smokey


agreed :p , I posted a question regarding what I thought (75%) had to be resonance, ie a tooth-filling-shaking-vibro hum from the engines at a certain rpm, which comes and goes depending on the throttle selection, and is , and I am quite clear and accurate about this, only ever present on taxi / commence taxi on the ground, but have never noticed it in the air.

[ExSimGuy]

Way back when the wide-bodies started to fly, I was building flight-sims for them. Obviously we didn't want to "re-invent the wheel", so we tried to use the designs (for the sim) that had served us with the older narrow-body machines.

However, with the wide-body aircraft came the high-bypass engines so, on the 747 and others, we had to add what was referred to as the "buzz-saw effect" to the simulated engine sound. (an extra circuit board added for each "engine")

I didn't now (until I read above) that it was due to fan tip speed, but it is something that I hear frequently on today's aircraft (I fly mostly in Airbus) and regard as normal.

[JamesT73J]

agreed :p , I posted a question regarding what I thought (75%) had to be resonance, ie a tooth-filling-shaking-vibro hum from the engines at a certain rpm, which comes and goes depending on the throttle selection, and is , and I am quite clear and accurate about this, only ever present on taxi / commence taxi on the ground, but have never noticed it in the air.

Jet engine sounds are fascinating.

Are you referring to that distinctive rasping noise? I've noticed this, and it seems to vary tremendously even if you sit in the same position relative to the engine. On CFM56 aircraft I always listen for it just after the brakes come off and the taxi starts. I usually hear it when a little power is applied to get the plane rolling, yet sometimes it simply doesn't appear.

Funnily enough, returning from holiday recently, and sitting just level with the fan cowling on an A320, the couple next to me commented on the buzzing noise from the fan with some curiousity. Just a couple of feet further back, it isn't audible at all. It is actually quite intrusive.

[junior_man]

The A 320 has an option of brake fans. This may be what you are referring to. They are somewhat noisy and would be used for 5 minutes or so after parking if the crew got the brakes a bit warm and were going out again soon.


No, this sound is only audible from outside of the aircraft, when the engines are shut down. It's very loud and only seems to last for a couple of minutes. I thought it might be the recirculation fans, but somebody suggested that it was something to do with the brakes cooling?? Not sure I understand how cooling brakes could make such a mechanical noise?????????

[alexban]

Indeed some of the buses use the same engine as the 737 NG ,the CFM engines.
Engine core is identical but the fan is bigger on the Bus-hence the difference in sound ,supersonic blade tips sound at high thrust.