• Jul 18, 2008
Toyota's Crown Hybrid gets brownie points for good gas mileage, but it's apparently a troublemaker in the motor noise department. Instead of merely adding insulation to the bulkhead, Toyota engineered an Active Noise Control system to reduce engine noise inside the cabin.

The contraption uses three microphones on the interior of the car to detect engine noise. Based on the frequencies they detect, one speaker in each of the front doors and a woofer on the rear shelf create antiphase signals to cancel out the noise. The canceling is set up to occur at passenger head level, and does not interfere with the music system or your own talking.

The Crown Hybrid, released this year in Japan, uses a slightly modified version of the hybrid system from the Lexus GS. Active Noise Control reduces cabin noise from the engine by about five to eight dB, and is permanently on. It's probably not out of the question that the Active Noise Control will make the jump to other Toyota products, and perhaps even Lexus models once they figure out how to put solid gold connectors on it.

[Source: Gizmag]


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  • 25 Comments
      • 6 Years Ago
      I think this technology is a great way to reduce the weight of sound deadening materials. Lighter vehicles are good, yes?
      • 6 Years Ago
      I certainly wouldn't pay for that if it was an option.
        • 6 Years Ago
        me too, I'd never PAY for that- I'm sure there's more worthwhile options avalible...
      • 6 Years Ago
      That's clever.

      Now is there a switch to make the hybrid engine sound like a V12 or a 426 Hemi?
        • 6 Years Ago
        Actually, that's existed a very long time too. Back when the Discovery Channel had that "Beyond 2000" show on TV (1990-1996 or so?) they had a british small car outfitted with noise cancelling technology, a rpm sensor, and a computer that could emulate the noise of many different engines. You could make it sound like a ferrari, v8, whatever you wanted. It was pretty cool. :)
      • 6 Years Ago
      Wow, offered on one Toyota in Japan. Here in the U.S. we get ANC in the Honda Odyssey, Accord, Pilot, and Acura RL.
      • 6 Years Ago
      Microphones in the headrests should be able to give the system some self-diagnosis.
      I have to say it's About Friggin' Time. I mean ever since noise-cancelling headphones came out, who hasn't thought, hey, Why doesn't my car do this? I hope they come out with aftermarket kits too. What a few microphones and a computer chip plugged into the Aux-In in my stereo? What's that, like $20?
        • 6 Years Ago
        The headphone noise control systems have it easy:
        The noise is coming at your ear really close to the microphone that is picking up the noise
        the anti-noise generator is really close by (the headphone itself),
        it doesn't have to calculate how much of a phase shift you have to make on the fly (the ear is right there and not moving around in the seat),
        the headphones filter broadband noise pretty well (turn off the cancellation in a headphone system and it is still muffling some noise),
        the interior environment of your ear canal isn't changing continuously (cars have biological entities that are moving about, distorting the acoustic space),
        etc.

        Cars are:
        a fairly reverberant environment (all that glass and plastic),
        have many noise sources at many locations,
        can change dynamically (opening a window, adjusting your seating position, getting warmer or cooler),
        have noise sources that cover the entire frequency range,
        etc.
      • 6 Years Ago
      A number of years back Nissan had a noise control system in one of their vehicle. As I recall, during the second model year they added an on/off button so that people could actually tell that it was working.

      Keep in mind that it takes roughly a 10 dB drop in sound pressure to appear to be half the loudness. So the 5 dB drop noted above is not that big of a change. And since it is likely to be affecting the combustion noise only, it's perceived effectiveness is probably not that good. At 60 kph and above, much of the noise you hear in your vehicle is from the tires, which are fairly broadband noise sources.
        • 6 Years Ago
        Lamric,

        Note that I said 10 dB is about a halving of loudness where loudness is a subjective measure. In an A/B listening test with headphones most people would catch a 3 dB change in sound. If I had most people (not acousticians) do ride and drives, they would be hard pressed to observe that difference unless it is pointed out to them given all of the other stimuli.

        The operative equation is dB = 10*log10(p^2/ref) , so doubling the pressure, p, is a 6 dB change.

        My comment about it being "not that big of a change" is that the system is likely targeting the engine order and not broadband noise so a 5 dB reduction of just that tone won't be that as noticeable. Imagine going to a concert and having one performer play 5 dB less. If the other performers are still going strong, that one performer's change will not stand out too much unless they happen to be doing a solo at the time. The engine order, particular above 60 kph isn't really a soloist in this situation. It would be the dominant noise when accelerating from a stop at slower speeds or just at slower speeds in general.
      • 6 Years Ago
      This idea has been around a very very long time.
        • 6 Years Ago
        +1

        This technology has been around for quite a while. It's plagued with problems though and doesn't play nice with aftermarket audio.
      • 6 Years Ago
      Meh. I really dislike this idea. Suppose something happens to your engine. You want to be able to hear what's going on. Mind you, I *own* a Corolla, and yes it's worked fine thank you very much... Except for that one time I kinda drove it off into a ravine, in the rain. Was literally 2 inches from a tree when it came to a stop.

      Now it has worked fine after I got it fixed, and I will say, those awful noises coming from under the car really helped me figure out the extent of the damage. If this ever makes it to the next Toyota I'm getting, I'm going to have it disabled.
      • 6 Years Ago
      Yes as opposed to "clueless" ford freaks :) !!!
      • 6 Years Ago
      Rob's formula should be like in the following:

      dB = 10*log10(p^2/ref^2) where ref is thresh of audiobility (2*10^-5 Pa)

      Therefore:

      double the Sound Pressure ---> +3db(A) in Sound Pressure Level
      • 6 Years Ago
      Can it also cancel out backseat drivers?
      • 6 Years Ago
      This technology is being used by other manufacturers right now..... I know for certain that Honda has had this in their Odyssey since 2005 and now in the Accord and the Pilot.
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