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Automatic Noise Cancellation Problem


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69 replies to this topic

#41 OFFLINE   stevedebi

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Posted 04 November 2014 - 04:58 PM

Can we not turn it off by simply turning the audio system off?

There is a fuse that can be pulled to shut down power to the system. It is in the owner manual.









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#42 OFFLINE   Smiling Jack

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Posted 05 November 2014 - 01:12 PM

.......

.......

 

Jack, this has *nothing* to do with the audio system.  It's designed to help with the noise produced by the CVT.  Here's an article:

.......

........

 

This would imply that the noise cancellation system has it's own separate speakers and amplifier(s).

 

I presumed that it used the audio system's speakers and amplifier(s).

 

Does anyone know which is the case?


Edited by Smiling Jack, 05 November 2014 - 01:13 PM.


#43 OFFLINE   jdbob

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Posted 05 November 2014 - 02:42 PM

"The DACMC is a digital signal processor that consists of an internal analog/digital converter, amplifier, and tone generator. The DACMC operates with the ignition in RUN, ACC, or OFF. Active noise control functions only operate with the ignition in RUN."

 

.....

 

"The DACMC receives engine rotation speed data and active noise control microphone input signals and calculates the targeted frequency needed to cancel engine noise within the passenger compartment. The DACMC outputs the engine noise cancellation frequency to all audio system speakers, except the instrument panel center speaker (if equipped), as fluctuating AC voltage."

 

So it uses the audio system's speakers and amplifiers.



#44 OFFLINE   bigalpha

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Posted 05 November 2014 - 02:51 PM

And the noise cancellation works even with the audio system in use?



#45 OFFLINE   stevedebi

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Posted 05 November 2014 - 03:27 PM

And the noise cancellation works even with the audio system in use?

Yes.



#46 OFFLINE   bigalpha

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Posted 05 November 2014 - 03:42 PM

That seems almost impossible!



#47 OFFLINE   Smiling Jack

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Posted 05 November 2014 - 04:56 PM

"The DACMC is a digital signal processor that consists of an internal analog/digital converter, amplifier, and tone generator. The DACMC operates with the ignition in RUN, ACC, or OFF. Active noise control functions only operate with the ignition in RUN."

 

.....

 

"The DACMC receives engine rotation speed data and active noise control microphone input signals and calculates the targeted frequency needed to cancel engine noise within the passenger compartment. The DACMC outputs the engine noise cancellation frequency to all audio system speakers, except the instrument panel center speaker (if equipped), as fluctuating AC voltage."

 

So it uses the audio system's speakers and amplifiers.

 

So, if the active noise cancellation uses the audio system's amplifiers and speakers, how on earth could it work when the audio system is turned off?

 

I note now that the only time I ever heard objectionable noise from the car was on my original trip home from the dealer after taking delivery.  I may very well have had the audio system turned off completely on that trip home, and I probably never again had it turned off completely while driving - though I often just turn down the volume to zero.


Edited by Smiling Jack, 05 November 2014 - 05:01 PM.


#48 OFFLINE   stevedebi

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Posted 05 November 2014 - 05:06 PM

So, if the active noise cancellation uses the audio system's amplifiers and speakers, how on earth could it work when the audio system is turned off?

 

I note now that the only time I ever heard objectionable noise from the car was on my original trip home from the dealer after taking delivery.  I may very well have had the audio system turned off completely on that trip home, and I probably never again had it turned off completely while driving - though I often just turn down the volume to zero.

 

The audio system is turned off, but the ANC isn't. Here is a pretty good explanation for the Fusion hybrid, from 2012.

 

http://corporate.for...58-active-37160

 

The entire point of the system is that it is sending out noise that exactly cancels out the noise detected by the sensors - so you hear nothing.


Edited by stevedebi, 05 November 2014 - 05:07 PM.


#49 OFFLINE   jdbob

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Posted 05 November 2014 - 05:43 PM

The microphones are connected to the module that drives the speakers, so turning off the audio system might just turn off some of the other modules (there are several) but leave the speaker amplifier module on.

 

On the other hand, just because it looks like things are off doesn't actually mean that they are. For instance it's typical that when turning off a TV satellite receiver that the only thing that will go off is the display and power LED, the rest stays powered.



#50 OFFLINE   Smiling Jack

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Posted 05 November 2014 - 06:33 PM

The microphones are connected to the module that drives the speakers, so turning off the audio system might just turn off some of the other modules (there are several) but leave the speaker amplifier module on.

 

On the other hand, just because it looks like things are off doesn't actually mean that they are. For instance it's typical that when turning off a TV satellite receiver that the only thing that will go off is the display and power LED, the rest stays powered.

 

Possible, I suppose, but that seems like an incredible (literally) stretch to me.

 

I think that it is more likely that only one set of amplifiers drives the speakers and that when the audio is off, those amplifiers are off and there will be no sound coming out of those speakers. It seems highly unlikely that two separate amplifiers would be driving the same speaker at the same time.  It also seems unlikely that the amplifiers would not be turned off with the audio system power, since they would be the principal power draw.

 

Maybe someone who actually knows will respond.


Edited by Smiling Jack, 05 November 2014 - 06:34 PM.


#51 OFFLINE   stevedebi

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Posted 05 November 2014 - 06:55 PM

Possible, I suppose, but that seems like an incredible (literally) stretch to me.

 

I think that it is more likely that only one set of amplifiers drives the speakers and that when the audio is off, those amplifiers are off and there will be no sound coming out of those speakers. It seems highly unlikely that two separate amplifiers would be driving the same speaker at the same time.  It also seems unlikely that the amplifiers would not be turned off with the audio system power, since they would be the principal power draw.

 

Maybe someone who actually knows will respond.

Jack,

The URL I provided states that it uses the audio system to produce the sounds that cancel out the noise. Is that not enough?

 

"The module instantaneously and continuously generates opposing sound waves. This reversed wave is directed through the Fusion Hybrid’s audio system, combining with the original engine noise wave to cancel out any potentially objectionable sound."

 

It seems obvious that they keep the amp and speakers active all the time. Maybe that accounts for some of that "other" energy I see on my left hand display, even when the HVAC is off.


Edited by stevedebi, 05 November 2014 - 06:57 PM.


#52 OFFLINE   jdbob

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Posted 05 November 2014 - 07:17 PM

Possible, I suppose, but that seems like an incredible (literally) stretch to me.

 

I think that it is more likely that only one set of amplifiers drives the speakers and that when the audio is off, those amplifiers are off and there will be no sound coming out of those speakers. It seems highly unlikely that two separate amplifiers would be driving the same speaker at the same time.  It also seems unlikely that the amplifiers would not be turned off with the audio system power, since they would be the principal power draw.

 

Maybe someone who actually knows will respond.

 

I didn't say there were more than one set of amplifiers. I said that there are multiple modules that make up the audio system. Those other modules don't drive any speakers, they only provide a number of audio inputs (such as the audio inputs in the center console, radio, satellite radio, bluetooth audio, etc.) to the amplifiers.



#53 OFFLINE   Smiling Jack

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Posted 05 November 2014 - 09:13 PM

Jack,

The URL I provided states that it uses the audio system to produce the sounds that cancel out the noise. Is that not enough?

 

"The module instantaneously and continuously generates opposing sound waves. This reversed wave is directed through the Fusion Hybrid’s audio system, combining with the original engine noise wave to cancel out any potentially objectionable sound."

 

It seems obvious that they keep the amp and speakers active all the time. Maybe that accounts for some of that "other" energy I see on my left hand display, even when the HVAC is off.

 

Could be, I suppose.

 

Once again, perhaps someone who actually knows will respond.

 

Otherwise I suppose there are a few ways we could test this out.



#54 OFFLINE   fbov

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Posted 07 November 2014 - 12:34 PM

I see no reason to doubt the explanation provided. It's not a stretch to most audiophiles (or audiofools depending on your point of view); separate amp and pre-amp/source installations are especially common in car audio. .

 

Amps can have more than one input, and newer Class-D amps have very low standby current draw, so there's no reason not to leave them on. You'd just be shutting off one of multiple sources to the amp when turning off the radio. Can you use the phone when the radio's off? From an engineering standpoint, doing otherwise is poor practice, as there's nothing critical in this feature that would warrant redundant amps, with associated weight and cost.

 

HAve fun,

Frank


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#55 OFFLINE   wb8nbs

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Posted 15 January 2015 - 11:18 AM

Noise Cancellation?  Didn't know we had this?  Is that why when I drive with the windows down or a window down it makes that offensive reverberation rumbling sound?  Interesting.  ;)

Cars make a very low (like 1-5 hz) vibration when you open a window because you have effectively turned the whole  passenger compartment into a giant whistle. Usually goes away if you open a second window which spoils the resonance of the passenger compartment.



#56 OFFLINE   wb8nbs

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Posted 15 January 2015 - 11:21 AM

The audio system is turned off, but the ANC isn't. Here is a pretty good explanation for the Fusion hybrid, from 2012.

 

http://corporate.for...58-active-37160

 

The entire point of the system is that it is sending out noise that exactly cancels out the noise detected by the sensors - so you hear nothing.

 

That URL is broken unfortunately.



#57 OFFLINE   bigalpha

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Posted 15 January 2015 - 11:24 AM

Cars make a very low (like 1-5 hz) vibration when you open a window because you have effectively turned the whole  passenger compartment into a giant whistle. Usually goes away if you open a second window which spoils the resonance of the passenger compartment.

 

And this car is particularly bad about the vibration. 



#58 OFFLINE   wb8nbs

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Posted 15 January 2015 - 11:48 AM


 

 

My ANC does not like passengers in the front seat for the most part. It's my daily driver and only when family of lunch buddies get in the car, the low db noise happens. Quite painful to everyone's ears and very embarrassing. Some of my passengers even put their fingers into their ears and say, "...make it stop.". At first, it does sound like the engine at low rpm, but you can easily prove, that it is the ANC. When it happens, just reach up and start tapping one of the over head microphones. The front passenger microphone works the best. If you hold the throttle steady when the drone is heard, start tapping the mic, and the noise goes away. Quit tapping, it immediately comes back. The front driver's mic has to be tapped slightly harder, and the rear mic even harder. The focus appears to be on the front passenger area. As tapping is awkward, especially when looking forward while driving and feeling the ceiling for the mic, I choose to increase/decrease the throttle. The only times by myself, that I can hear the db noise start, but never reach the full drone stage, is in music on Sirius XM radio. It will sound as if you set a sub woofer to low in the db, then it begins to distort the song. I listen to 80s, Message, and Boneyard. It's the base guitar/keyboard, that brings it out.

 


 

Where exactly, are the three microphones located?



#59 OFFLINE   62Lincoln

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Posted 16 January 2015 - 06:18 PM

Where exactly, are the three microphones located?

 

 

 In the headliner.



#60 OFFLINE   Blue Tom

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Posted 16 January 2015 - 08:22 PM

That was one of the only things that a saleswoman pointed out on our first C-Max test drive.  My wife was commenting that it seemed kind of noisy on the highway.  The sales gal said "well, the typical response would be to turn up the radio and say, 'What noise?'"  Then she pointed out the microphones and explained the ANC, which I thought was pretty cool.  The audio happened to be off at that time during the test drive, FWIW.  But since we bought the car, I've actually noticed a lot less engine noise/vibration than I remember on that test drive.  Probably was just more sensitive at the time since we were looking for flaws.  I still think it's cool that they include it, but I can't help but think it was just an engineering requirement because they couldn't mechanically suppress it to acceptable NVH standards.  Some sports cars play artificial engine noises over the speakers because their cabins are so quiet.  The C-Max, with its tiny engine, does its best to eliminate the engine noise from the cabin.  Different strokes for different car buyers, it would seem.  Personally, I wouldn't mind an option to pipe in some sweet V8 burbles that are synced to the throttle. You know, for irony.  But that's just me.


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