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Noise-Cancelling Tech: A Key To Quieter, Higher-MPG Hybrids?

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2013 Ford Fusion Hybrid

2013 Ford Fusion Hybrid

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One thing common to many hybrid cars is the twin-pronged benefit of refinement and silence.

Just a brief drive in a hybrid is usually enough to confirm that, at low engine speeds at least, they don't produce a lot of noise. Even less when running in electric mode.

Still, there are always improvements to be made, and engineers at Bosch are looking into noise-cancellation techniques in order to reduce the noise hybrids make as the engine switches on.

As Wired reports, Automatic Noise Cancellation (ANC) is nothing new, and has been used for years to reduce noise in luxury cars.

But with fuel-saving techniques like cylinder deactivation, and with hybrid powertrains where the engine switches on and off, the noise generated can be more apparent due to a change in frequency of specially-designed engines.

Dr. Takeshi Abe, who worked on noise, vibration and harshness on the 2013 Ford Fusion Hybrid, explains that the unique firing order of the engine actually creates quite a boomy, unpleasant engine noise.

The Fusion Hybrid actually uses ANC--a technique that acoustically cancels out noises by generating an out-of-phase noise at the same frequency--to cancel this boomy noise.

That means the car can be made more efficient without sacrificing passenger comfort, and without loading the car with excessive levels of heavy sound-damping material. And efficient it is: The 2013 Fusion Hybrid manages 47 mpg combined.

Honda will also use the technology on its upcoming Accord Hybrid, but actually uses it on every variant of the 2013 Accord. Honda says the technology lowers the sound pressure level by about 3 decibels, in a range between 1,000 and 2,000 rpm where uneven engine pulses can create a harsh sound.

By actively cancelling noises produced by the engine, automakers can make their engines more efficient than ever before--and in the case of hybrid cars, make them even quieter...

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Comments (10)
  1. I mentioned to an office-mate that the C-Max hybrid has noise cancellation to reduce engine noise. She quickly replied with can that be used to reduce the noise from the children.
     
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  2. Ah, if only. Active Noise Cancellation for passengers...
     
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  3. *Automatic Noise Cancellation
     
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  4. That reduces the noise inside the cabin through its sound system.

    But that usually doesn't reduce any noise generated outside the car for the neighborhood...
     
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  5. True, though around my own neighborhood traffic moves slowly enough that hybrids would all be in EV mode anyway.

    Tire noise is actually a greater problem outside most modern cars. Most subcompacts seem to have tires like 1970s supercars these days.
     
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  6. Not hearing the logic here… "By actively cancelling noises produced by the engine, automakers can make their engines more efficient than ever before".

    Energy lost to noise is many orders of magnitude smaller than power output of the engine & engine efficiently. I'd tend to argue that the ANC requires additional energy from the motor, making it less efficient (but better sounding).
     
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  7. Sorry, I perhaps didn't make it clear enough in the article.

    Some of the techniques used to make engines more efficient, altering firing orders for example, can result in unpleasant noises from the engine. By using ANC, manufacturers can do whatever they like to increase efficiency without it becoming uncomfortable for the passengers - i.e. by using ANC, carmakers can make their cars more efficient without incurring refinement penalties.
     
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  8. Finding it interesting that the Ford Fusion "Hybrid" makes too much noise & uses Active Noise Cancelation (ANC) technology.

    In comparison the Ford Fusion ST ("Sport Technology") model isn't loud enough, so uses an Active Sound Symposer (ASS). See link(*) below for details on how sound is enhanced on the ST model. The symposer is basically a pipe from driver to the engine compartment to increase sound while accelerating.

    (*) http://wot.motortrend.com/video-find-2013-ford-focus-st-active-sound-symposer-gets-you-through-the-day-273185.html

    Take away… acoustic engineering is important part of a vehicle design as it relates to driver experience & expectations.
     
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  9. Indeed, you raise an interesting point.

    It's worth pointing out though that with the Fusion, Ford isn't so much reducing noise as a whole, but reducing unpleasant audible frequencies, such as those as the engine turns on, or those in a particular RPM range.

    With the ST, I expect these frequencies don't naturally occur as the engine is tuned more for performance than economy - but at the same time, all the sound-damping material and modern tech means that even performance engines are quiet these days - and buyers want a little more noise!

    You're right though, it's an interesting subject and very much related to driver expectations.
     
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  10. Active noise cancellation in a fully electric car is unnecessary. It's already quiet.
     
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