Loud noises!

[billharnois.livejournal.com]

Airplane noise is up 3X in Davis area this year. This is confirmed by Somerville Transportation Equity Partnership (STEP) and our mayor. You may or may not have read the articles in the news. Both STEP and our mayor have encouraged people who are annoyed by the noise, to call this number and complain:

(617) 561-3333

Here is some more info:

http://www.somervillestep.org/mt/mt-search.cgi?search=logan

The more people that call and complain the better chance we have in getting a reduction in overhead flights (so we're told).

If you don't care about the increase, or don't care about planes flying by every 40 seconds, please read all of the witty responses below instead.

Comments

[derekp.livejournal.com]

A lot of people seem to be of the opinion that the desired result of complainers is that logan re-route air traffic. Could enough real pressure be applied to Logan, State, and Local governments to enact some legislation requiring a move to quieter planes?

[mkb-technologie.livejournal.com]

LAX has limits on what times planes can land because of noise ordinances, so possibly, Logan's acceptance of louder planes landing at particular times could be curtailed.

[http://users.livejournal.com/_mattt/]

Yes.

I believe this is the appropriate action. I'm not sure what say Logan has in the noise level of aircraft, though.

[derekp.livejournal.com]

They are first in the pecking order when it comes to deciding who can and cannot fly out of and into the airport, no?

[xuth.livejournal.com]

With the lifetime of an individual plane being 30 years or more and the design phase being 5-10 years, even if you could get a law passed to make quieter planes, it would take a very long time before any effects were noticable.

[derekp.livejournal.com]

That's the thing. Quieter planes already exist. If you want evidence of this, just stand on one of Somerville's hills on a high flight activity day and listen to the noise differences between different planes on similar paths and at similar altitudes.

[xuth.livejournal.com]

That seems... completely unreliable. I know that I would be unable to compare flight altitude of two planes unless I had reliable information on relative size. Furthermore, two identical planes at the same altitude will be making very different amounts of noise depending on what they're doing (takeoff vs cruise vs landing) and the direction they're facing relative to the listener. Other fun differences to consider is how the plane is loaded. One plane might be at twice the load of the next one.
That said I agree that some planes will be quieter in general but I'd be willing to bet there's a much greater correlation to noise by weight of plane* than by efforts of engineers to reduce noise.

*this is excluding things like fighter jets that are capable of some impressive sound pressure without resorting to sonic booms.

[zonereyrie.livejournal.com]

Actually, no. An old narrow-body can easily produce more noise than a modern widebody - despite being smaller and lighter. Engine technology makes a huge difference - in both raw noise and *perceived* noise. Some frequencies are much more noticeably than others. Modern high-bypass turbofans product a lower frequency and a lower total volume to boot, compared to the old low-bypass turbofans - let alone straight turbojets on the earliest jets.

For example, the Boeing B737-100/200 used P&W JT8D low-bypass turbofans. Some of these are still in operation - Southwest still has some, USAir still has some, etc. The engines are long, narrow nacelles nestled up against the wing.

The B737-300/400/500 was a minor refresh to the design which updated the engines to the CFM International CFM56 high-bypass turbofan. Airframe changes were minor, though there was a 'stretch' to increase the size of the cabin (carry more passengers). So you have very similar aircraft - with the newer revision being a bit bigger and heavier - but noticeably quieter.

(The later B737-600/700/800/900 Next Generation aka B737NG was a much more extensive redesign. It uses newer, more powerful versions of the CFM56, has a new wing, new landing gear, redesigned cabin, new cockpit - major changes. This is the model line still in production today.)

There are other examples - the old DC-9 family was updated over the years as the MD-80 family, MD-90 family, and finally the MD-95 aka B717 (after Boeing bought McDD). Similar airframes, but each generation used newer engines. And despite growing larger over time, they got quieter. Though there are a lot of DC-9s/MD-80s still flying (often called the 'Super-80' - originally the DC-9-80 and then the MD-80 when McDonnell merged with Douglas.)

And sometimes they just re-engine older aircraft to comply with new noise regulations. Old B727s have had their three JT8Ds replaced with two Rolls-Royce Tay's (the middle engine is faired over). There are B707 and DC-8s still flying for cargo airlines with their old engines replaced by modern ones like the CFM56 to comply with international noise and emission regulations.

So newer engines and engine technologies definitely help - but after making dramatic gains over just a couple of decades, the pace is slowing. Most of the 'easy' fixes have been done. Now it is down to some serious engineering - and there are active programs run by Boeing and Airbus, as well as governmental groups. Acoustic liners in engine inlets cut some noise, and there is work on acoustic lips for the nacelles - but they need to make sure they handle icing properly. Scalloped edges are beginning to appear on the exhausts of newer jets like the B787 and B747-8 to reduce exhaust noise. Sometimes small changes make a difference - I forget which airliner it is, but just changing the shape of the holes on the leading edge (anti-icing system IIRC) eliminated a 'whistle' which was like blowing across a soda bottle.

Boeing's Quiet Technology Demonstrator programs (QTD1 and QTD2) have produced some amazing results which had fed directly into development of their latest airliners, and will continue to feed into new designs.

Hmm, this got to long...

[zonereyrie.livejournal.com]

But airliners have a lifespan of decades, and it can take ten years for new concepts to make it from initial proposal to service delivery. So it takes a while for older aircraft to age out of the fleet. And air travel is too important to the economy - global and national - to force the airlines to update. They can't afford to turn over their fleets too often. There are some pressures that help - international noise regulations cause them to spend money updating older aircraft with hush kits or re-engining programs, or not flying them into certain markets, and that eventually reduces the value of the aircraft to the point where a replacement makes sense. High fuel prices have also greatly accelerated turn-over - older aircraft are less efficient, both aerodynamically and in their engines, and they require more maintenance, so their operating expenses rise - making it more cost effective to replace them.

If all things are equal - sure, a modern commuter jet with maybe 20,000 pounds of thrust isn't going to generate the noise of a new B787 with over 230,000 pounds of thrust - and several times the mass - but an old jet can be louder than a newer jet that is much larger due to the differences in aerodynamics and engines.

[ukelele.livejournal.com]

Man, it's always so nice when people who actually know stuff chime in. :)

[zonereyrie.livejournal.com]

Modern aircraft are already FAR, FAR quieter than just 20 years ago. There are international regulations on aircraft noise, and they're increasingly stringent. There just isn't much more they can do on noise to get the kind of dramatic reductions already produced - all the low-hanging fruit has been plucked.

And it is becoming a trade-off - noise or pollution? There is pressure to make aircraft increasingly more efficient as well - reducing fuel-burn and pollutants. But one of the most promising concepts is the Un-Ducted Fan aka Open Rotor - but they're much more noisy than today's high-bypass turbofans. You can have quieter or you can have dramatically more efficient - pick one.

Boeing and Airbus both have extensive research programs going into quieting aircraft. Engine noise will continue to be reduced, though it will be smaller gains than in the past. The new B787 uses scalloped edges on the engine's bypass to reduce noise - the first aircraft to do so. And the newer B747-8 uses scalloped edges on both the bypass and core exhaust for further reductions. (The research to use it on the core wasn't ready in time for the B787.) Some of the major focus is now on airframe noise - wind noise around extended flaps and landing gear, etc.

But, no matter what you do, a jet is loud. You can't have exhaust gases rushing out of an engine, and air flowing over an airframe at a couple hundred miles and hour, without producing noise. So you'll never have a really quiet aircraft.

But, as I said, what we have today are a LOT quieter than older jets. High-bypass turbofans are much quieter - with a lower frequency - than the old shriek of the low-bypass turbofans, or the straight turbojets, used on older aircraft. And while some of those older jets are still flying, most have been retired and more are retired each year - and most of those flying have been fitted with hush kits to reduce their noise.

(Yes, I'm an aviation geek - I read Aviation Week, Air&Space, Flight Journal, etc, religiously. :-) )