Noise cancelling speakers help 2010 Chevy Equinox get +1 mpg
The new 2010 Chevy Equinox that was unveiled at the Detroit Auto Show has an interesting new bit of technology that aids fuel efficiency even though most people wouldn't think of it that way. When the engineers were working on the calibrations for the new 2.4-liter direct injected four cylinder engine, they were able to get some significant fuel economy improvements by lowering the idle speed and by lowering the speeds at which the torque converter locks up. Unfortunately there were some downsides. The new calibrations resulted in some very annoying low frequency (33-100 Hz) noise that would be unacceptable to most customers.
In the past, the engineers might have avoided those kinds of calibrations and just taken the hit on efficiency. This time however, they got approval to employ active noise cancellation. A pair of microphones embedded in the headliner listen for those frequencies and then generate an opposite wave sound from the audio system speakers to cancel out the offending noise. By using this technology to offset the negative NVH effects, they were able to get a one mpg improvement in economy for the four cylinder Equinox.
[Source: Chevrolet]
Reader Comments (Page 1 of 2)
Drew 8:57PM (6/10/2009)
And the people outside the car? They all just get to suffer with the unacceptable noises. I'm assuming any noise canceling system with windows up on the car wouldn't alleviate the people outside it... or does this only occur when its moving?
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Throwback 9:35PM (6/10/2009)
All cars have to meet external noise limits, modern cars in general are very quiet.
why not the LS2LS7? 11:32PM (6/10/2009)
It only occurs when moving. Your torque converter is never locked up at idle or else the engine would stall.
MikeW 12:25PM (6/11/2009)
Maybe not.
Some transmission decouple an internal clutch pack, if you are holding the brake, to lower the engine idle speed.
So if the transmission is out of gear, the converter could be locked up-to try and reduce heat build up in the transmission.
UH2L 10:20PM (6/10/2009)
Great idea! That's definitely innovative outside-the-box thinking.
Oh wait a minute. According to many of you, GM doesn't know how to innovate, right?
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phoenexius 10:26PM (6/10/2009)
and you won't hear the ricer's booming bass, sweet
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rob 9:10AM (6/11/2009)
I suspect the system is tied to the engine RPM since it makes things simpler and cheaper. If that is the case, it will know nothing about the sound coming from outside the car except near the engine RPM. Now if the boom boom is exactly at the problem frequency then you may see some benefit...unlikely.
The only way to limit you exposure to the rice boy's booming is to cover your vehicle in a nice and heavy barrier... or better yet...cover his vehicle!
oldraven 10:57AM (6/11/2009)
The article says the microphones are embedded in the headliner. That means it'll cancel out any low frequency noises getting through to the cockpit. It must be tied to the stereo, though, since cancelling out those frequencies would be a huge PITA for owners.
usbseawolf2000 10:33PM (6/10/2009)
The Accord V6 Hybrid used active noise cancellation when it ran on 3 cylinders. I think if you roll down the window, you'll hear the annoying noise. Honda no longer make it.
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Jimbo 1:35AM (6/11/2009)
Honda still employs Active Noise Cancellation on all their vehicles with VCM, including the Odyssey, Pilot, and Accord.
JH 1:08AM (6/11/2009)
Oh god, this is so, so wrong. "Cute" or "clever hack" but wrong. Only GM would not only let this leak out of the company ... but actually brag about it. It's like a Dilbert cartoon brought to life.
Good engineers trace the problem and fix it. Bad ones slap on a band-aid. (Or, bad managers make engineers apply cheap band-aids.) Pile on a few dozen of these "innovative workarounds" and you wind up with an overly complicated and delicate system that is very difficult to work on and more prone to failure.
The right thing to do is to track down what's making the noise (engine, torque converter, whatever) and fix it so that it doesn't hum at idle speed. Instead, you end up with a band-aid where, from now on, every time they make a tweak to the drivetrain, they now have to get the stereo people to recalibrate something else. If there are different stereo options and/or this "fix" gets applied to other vehicles with this engine, then you can multiply the time wasted by each of these variants. The result is a web of cross-interactions that complicate and therefore slow down all future development and bug fixing. And when things are complicated, there are more bugs that slip through. You also have to waste a lot of money documenting this "feature" ... service manuals and training materials for dealers have to be changed so that techs know that humming at idle is "normal" for this particular model of this vehicle. Oh, and what happens if a customer puts in an aftermarket stereo and realize their car is making noises? So you have hundreds of people either taking their cars in for service or silently seething that this is the last GM product they'll ever buy.
Car companies that succeed are the ones that never intentionally put unfinished components with known defects into products. Then there's GM. I mean, why produce reliable product via incremental change like boring Toyota when you can do it fast and loose, British Leyland style!
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GoRealSlow 1:33AM (6/11/2009)
http://www.motorauthority.com/toyota-develops-noise-cancelling-system-for-car-interiors.html
Jimbo 1:41AM (6/11/2009)
There are some things like low-frequency sounds that can't be engineered away. They're fundamental. If you lower the idle speed, a piston engine is going to fundamentally vibrate at an annoying frequency. You may be able to minimize by beefing up the engine block, but it won't go away completely and you've added mass which would offset the fuel economy gains.
As far as the sound outside the car, who gives a rat's ass? As long as I can enjoy the sound while I'm inside the vehicle and it's not giving off sounds that would violate noise ordinances, that's fine with me.
Roger 3:27AM (6/11/2009)
I know a sure way to stop idling vibrations.
.
.
.
A start-stop system.
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Chris 11:09AM (6/11/2009)
GM already has this with their BAS system (See Malibu, Vue, Aura) but they prefer to sell that as a "hybrid" and charge much more for it.
What a joke...
Why not look somewhere else for that 1MPG, instead of hacking together a solution like this.
john 10:42AM (6/11/2009)
please toyota innovate something ,please the japaneese ability lies in copy and paste,they borrow others ideas and claim them as their own noise cancelling cars have been around for years ,lexus has a commercial out now about rainsensing wipers i have had that on my GM cars now since at least 2000,and they are bragging about it now,Now that the yen is were it should have been for the last 20 years we shall see how much money they make going forward............do they make nice cars of course they do,but they have not been alone in that department for quite sometime now it takes the slow american public to catch on
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UH2L 11:04AM (6/11/2009)
Add to that list of GM firsts the following...
- Heads Up Display (on windshield)
- Steering wheel controls
- Cooled seats
- Automatic high beam adjustment (Intellibeam)
- Magnetorheological suspension (now being used by Ferrari)
- etc...
That being said, the fact that brands like Lexus make a big deal of them is partially a testament to poor advertising and GM public relations who don't know when to toot their own horn or to do it properly. But then, maybe people just ignore it because it's not Lexus talking.
Tim 9:09AM (6/11/2009)
I wonder if GM will use this tech to cancel out the noise of the range-extender.
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rob 9:15AM (6/11/2009)
Most engineers will try to "trace the problem and fix it". Until they realize that they are up against the laws of physics, like F=ma. At that point they employ the band-aids.
Now since some members of congress have suggested having some of those laws changed then maybe there is a chance (see David Cole's quote at the bottom)....
http://www.snopes.com/politics/obama/physics.asp
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kballs 4:51PM (6/11/2009)
Uh, you misplaced the decimal point! It's 0.1 MPG.
From motor trend's article:
The noise-cancellation system also allowed engineers to drop the idle speed of the I-4, which yielded about 0.1-mpg-better fuel economy. Further noise mitigation is attained through the use of laminated acoustic glass for the windshield and front side windows as well as triple seals on all four doors.
http://www.motortrend.com/roadtests/suvs/112_0909_2010_chevrolet_equinox_review/engines_interior.html
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