Questions tagged [noise]

Questions related to aviation sound noise or regulations thereof.

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2answers
414 views

Why are jet engines still so noisy?

In general, jet engines on passenger aircraft make so much noise that in a long-duration flight it becomes really tiresome and uncomfortable. Nowadays, technology is much more advanced than before. ...
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5answers
3k views

Does any of the hearing protection worn by aviation professionals use active noise reduction?

I have read that passive hearing protection (standard earmuffs/plugs) offer good protection against higher frequency noise but do not protect as well at lower frequencies. Supposedly active noise ...
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0answers
116 views

What causes "the howl" on the Trent 700 engines?

Many people have noticed what they call "the howl" on the Airbus 330 with Trent 700 engines, usually for a brief moment when it breaks inertia from idle setting. It sounds like this: ...
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1answer
125 views

Why do some Airbus jetliners at full thrust sound like turboprops? [duplicate]

When riding an A3xx I always noticed the unique "turboprop" like sound when close to full throttle. Why is that so?
12
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1answer
2k views

Why do flying wires hum louder in a sideslip?

Page 50 of the Feb. 2021 issue of the EAA's magazine Sport Aviation reports that Like any good vintage airplane, the Sea Bird likes to fly coordinated, and the flying wires will sing out loud if the ...
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2answers
169 views

Whenever I hear a plane throttling down quickly, what is happening visually?

I am completely blind and have heard this several times when I was at air shows. Then my friend sent me this recording of a crop duster spraying the fields, and I heard the same type of sound. It ...
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0answers
41 views

Why would changes in jet-engine power settings not result in changes in engine loudness?

My casual AAR reading has dredged up another counterintuitive detail of aircraft behaviour, this time regarding the relationship between engine power and engine loudness: 1.16.7.3 Sound Similar to ...
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0answers
81 views

Odd whining sound from planes passing over [duplicate]

I'm trying to figure out what is causing the sounds that I'm hearing from planes passing over my house. I'm located approximately 60 miles NW of ATL. The noise I hear sounds like a turbine rapidly ...
7
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1answer
299 views

What causes the horn-like noise during the start-up of some jet engines?

Here's the specific sound I'm talking about (it starts specifically 56 seconds into the video, as well as at 2:02 for the second engine): I've only really heard that ...
2
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1answer
112 views

Do thrust reversers make more noise than engine at same RPM?

I'm talking about general aviation jet engines here. I live near an airport and I rarely listen engine noise on takeoff but always hear one during landing. Would a jet engine at the same RPM make more ...
12
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5answers
10k views

What could explain the fact that during 1976-80, I used to hear commercial jets make sonic booms while flying overhead?

I've read on this site & on Wikipedia that there have only been a couple of commercial jet planes in history that have broken the sound barrier--either in testing (without passengers) or during an ...
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0answers
134 views

F-16: MAIN PWR ticking sound, what is it?

What is that sound that starts when MAIN PWR switch is turned on in the F-16? Its sorta like a fast ticking sound. Why is it there, what makes it, when does it stop? And is it also there when only ...
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2answers
311 views

How to reduce the noise of the supersonic passage(bang)?

as you know the transonic phase is often associate with the bang. The principal cons of the transonic phase is the noise,it's why there is not supersonic passenger aircraft( cause the end of the ...
3
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1answer
391 views

What's the rattling noise on an A320?

I recently flew on an A320, and during takeoff when the aircraft was rotating, I heard a loud rattling noise. If I had to guess I would say it came from the gear below but I can't be sure. I was ...
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0answers
161 views

Could propellers benefit from the design of the Blue Edge rotor?

Source: wired.com If indeed the Blue Edge blades reduce noise by 50%, could the similar design be used on [forward-facing] propellers without a penalty in speed or agility?
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1answer
244 views

Could a shrouded fan blade with long chord length be efficient?

I am wondering if it would work to have a fan with two or three blades which have short-ish span and very long chord length, like half a rotation for each blade. Would a shroud (that is molded on the ...
5
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1answer
485 views

What’s that weird sound during spool up on some aircraft?

Some engines seem to make this characteristic “wailing” noise when spooling up. A good example of such is from 0:50 to 0:54 in the following video: . I’ve also heard ...
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6answers
6k views

Is an afterburner louder than the same jet engine without it?

I would speculate that an afterburner increases the noise because it is nearer to the exhaust. But it certainly causes so many changes in the exhaust flow that it could be less loud as well. It may ...
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1answer
5k views

Will you be able to hear a supersonic aircraft flying away from you?

I'm wondering if you could be able to hear the sound emitted by an aircraft say traveling at Mach 2 away from you. I wondered if it might shift the emitted frequencies beyond the audible range. Would ...
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3answers
221 views

Why are the first sounds of an approaching enroute airliner low frequency, booming ones?

Often I will hear an intermittent, low frequency, powerful, booming sound that resolves into that of an airliner flying enroute high (FL 300+) overhead. So the first sounds that an airliner flying ...
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2answers
3k views

Why is a Lockheed MC-130J Commando II creating such a loud droning sound?

Today I heard a loud droning sound which is really unusual in the area of west London I live in; so I went on ADS-B exchange and it showed a USAF Lockheed MC-130J Commando II flying literally right ...
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2answers
208 views

How does the noise of a 2-to-4-seat helicopter compare with that of a similarly-sized fixed-wing aircraft?

We are considering allowing helicopters on our private airstrip (2600 ft strip). Noise on the ground (and approach) is the concern from the community. Does anyone know approximate dB ratings for a ...
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2answers
8k views

What is the loud noise of a helicopter when the rotors are not yet moving?

What is the loud noise when a helicopter is ready to start flying, but the rotor is not yet rotating? For example at Trump's "chopper talk", when he is intercepted by reporters on the way to Marine ...
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2answers
7k views

Why don't modern jet engines use forced exhaust mixing?

Jet engines are noisy[citation needed] - even a modern high-bypass turbofan is still deafeningly loud compared to pretty much anything except the even-louder low-bypass turbofans or a turbojet (much ...
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6answers
3k views

Is ear protection necessary for General Aviation aircraft?

What would happen if someone flew a brand new Cessna Skylane/Caravan or a Robinson R22 without using earplugs or headphones? Would they get hearing damage or it would be just a little bit loud where ...
4
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1answer
1k views

What is the cabin noise hertz in typical commercial aircrafts?

In cabin, we hear noises in commercial aircrafts. Wondering if it is in general over or under 100 hz. There should be a band width. Thanks!
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4answers
250 views

Can ADS-B used for voice communications?

Everyone knows the radio communications doesnt sound great altough they work perfectly. But can the brand new ADS-B communications be used for carrying audio signal? Would it be clearer? The ADS-B ...
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1answer
813 views

What kind of microphones does aviation use?

Do they use the dynamic ones or cheap ribbon ones? Also why are these microphones so small? I guess they dont use condensers. (I am yet to see an 3.5mm jack (which is used both on the C172 and the ...
12
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1answer
2k views

What causes the sudden spool-up sound from an F-16 when enabling afterburner?

What causes the sudden spool-up sound from an F-16 when enabling afterburner? I've included a video to make it clear what sound I'm referring to: at 1:16, I assume ...
2
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1answer
271 views

What causes the nose landing gear knocking noise on a Boeing 777 while taxiing?

The NLG knocking noise heard on taxi-in to stand, what could cause this knocking noise?
2
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1answer
231 views

Can helicopter rotor produce infrasound?

While watching a Mil Mi-17 helicopter takeoff I experienced strange thing. The helicopter produces a lot of noise even when just starting the engines. But shortly before taking off the high-pitched ...
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1answer
669 views

What's the mechanical 'whoosh, whoosh' sound in this video?

Sound in question comes right after the warning sound at 22:57.
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0answers
648 views

Why are the cabin chimes one semitone lower on the Boeing 747-400 than on other aircraft? [closed]

I noticed that the cabin chimes on the Boeing 747-400 overall sound one semitone lower than on other aircraft, including the 737, 777, Airbus A320, and even the 747-8. The same semitone-lower chimes ...
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1answer
1k views

What are the unique sounds emitted by Embraer E190-E2 on final?

I live close to an airport where these aircraft frequently land. When the E2 is between 2-3 thousand feet, something which I can only describe as whale moans, is heard. I say they are unique because ...
26
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3answers
5k views

Why would a turboprop rev down just before going full throttle during takeoff?

The only turbprop I've travelled is the ATR 72. I've noticed that the props' rev go down (for like a second, the sound also goes down) just before engaging full throttle in order to takeoff. I've ...
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0answers
262 views

In terms of noise, how does a steep climb-out compare to a noise abatement procedure?

For airports in populated areas, it is common to implement noise abatement procedures. In practice, this means that aircraft reduce thrust on departure, so that noise is reduced in proximity to the ...
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2answers
5k views

Are there any reported cases of noise from helicopters causing damage to property?

In the Netherlands, three cases have been reported of Chinook helicopters' rattle noise (low frequency sound) damaging solar panels. The Dutch defense ministry recognises this problem and the lawyer ...
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1answer
647 views

Is there any way to reduce the noise and vibration in a C-130 Hercules?

We are using C-130 B and E Models with T-56 A-15 engines and Hamilton Sundstrand 54H60-91/117 propellers. A lot of vibration and resonance are felt on these military version aircraft even after using ...
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1answer
703 views

Why does the Apache create much more rotor noise than the A-129?

The AH-64 Apache attack helicopter was upgraded several times after its first flight in 1974. The Apache Longbow was a major upgrade which entered service in 2003. On the other hand, Agusta A-129's ...
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2answers
720 views

What are ways to reduce drag and noise generated by the landing gear?

Apart from using fairings, what ways are there, or have been studied, but not necessarily implemented in reducing drag and noise produced by the landing gear, mainly for commercial aircraft with ...
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1answer
375 views

What is the maximum decibel noise level of a stage 4 rated engine?

I was just wondering if anyone is able to help me. I need to find out, what is the maximum decibel noise level of a stage 4 rated engine (as defined by the Federal Aviation Administration)? Some more ...
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2answers
2k views

What causes the "growl" of some large turbofans at takeoff thrust?

There are some (all?) large turbofans which emit a distinct "growl" (some people call it a "buzzsaw" sound) at takeoff thrust. What causes it? I've seen it explained (as in this question) as the fan ...
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2answers
468 views

What noises are considered worrying on a passenger flight?

As a typical 'nervous flyer', I often find myself asking crew about a noise that they say is completely normal during flights. The thing is, I've flown a lot and still hear new sounds sometimes! For ...
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9answers
7k views

Why are winches not used for towing commercial planes up?

In this video a glider is pulled up by a winch on the ground, like this: (Source) I would say you could apply the same principles with bigger planes, possibly even using sustainable energy sources. ...
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1answer
148 views

How to deal with the noisy cockpit?

From the pilot perspective I want to know how to deal with the noise in the cockpit on the turboprop aircraft while long-run flights. The reason is old type aircraft with bad headphones which doesn't ...
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1answer
170 views

Do noise abatement procedures have an impact on aircraft emissions?

The ICAO has imposed Noise Abatement Departure Procedures (NADP1 and NADP2) in order to limit the noise impact of departing aircraft on communities living nearby airports. Could noise reduction lead ...
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3answers
2k views

When a typical commercial airliner flies overhead, what is the actual noise we are hearing?

We're all familiar of the sound planes flying quite high overhead and you hear a faint drone, even when planes are lower to the ground you hear them scream at a slightly higher pitch, but what exactly ...
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0answers
135 views

How do active blades work on helicopters?

Can someone throw some light on 'active blades' as used in helicopters? I'm mostly interested in the use of piezoelectric material and actuators. How are the actuators able to sense the change of ...
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1answer
768 views

What are the rules in the UK about overflying built-up areas for fun?

I live in North London. It's not like we don't have a fair amount of noise pollution from the sky, with helicopters, and jets landing at LHR with a stupidly shallow glide path angle. But in addition,...
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3answers
3k views

Won't sonic booms prevent Space X's BFR intercity transport plan from being acceptable?

Considering that Space X have just announced that their BFR can take anyone anywhere in the world in under 1 hour, that would be enormous speed, does this rocket not produce sonic boom? If not is it ...