2015 YUKON NOISE IN CABIN

Wrench589 · January 16, 2015

wrench589 - I have a separate 140 page MyLink specific manual provided from the dealer. There is an IntelliLink manual, I downloaded it.

Can you post the link for the one you downloaded?

jasondenali15 · January 16, 2015

Officially driving the vehicle with a disabled ANC. The mic on the passenger side was disconnected, thus disabling the ANC. To be honest, it may help the booming ever so slightly. Negligible at best. The ride is very quiet in 8 cylinder mode...I would say an improvement. Not so much in 4 cylinder mode. That's why I think it's only a slight (at best) improvement. They kind of wash each other out. Keep in mind I drove it for only a half hour at varied speeds, and it's just one guy's early opinion...

I think the ride would be just fine if it did not go back and forth from 8 to 4 cylinders. Considering the vehicle does that frequently, and I still noticed the sound prominently every time it made the switch, I can definitively say disabling the ANC does not help...In my opinion.

I will keep paying attention to it over the next week or so.

The Zip · January 16, 2015

So the thread goes on, disconnecting the one ANC mic may not be the answer, the other two mics may be compensating. The one mic did help slightly, but no cigar. The answer may not be to disconnect the mics but to muffle them, which is what 20sierra14 did. Based on his input, the issue of buffetting did not decrease slightly, it stopped.

So, an improvement to what 20sierra14 did may be the tolerable fix. 20sierra14, explain exactly what you were experiencing and what stuffing cotton into the mic-wells did to mitigate that issue.

wrench589 - http://www.gmc.com/intellilink-infotainment-system.html

The Zip · January 16, 2015

jasondenali15 - Unless the dealer knows that the driver side mic is a "master switch" for ANC, this does not jive with my research. Reseached showed me that the ANC capability exists in "each" mic, which by disabling one mic should not disable ANC. As a manufacturer (Bose), I would incorporate this as a fail safe. And in essence that's what they say, ANC begins with "the" mics, not "a" mic.

What prompted the dealer to disable that mic, did he have knowledge that "one" mic would work? What was your complaint and what did the dealer do (specifics will be on the work invoice). Copy and paste the invoice if you can, thx.

Anon2015 · January 16, 2015

I would suspect the mics are doing some variety of spatial averaging.

Wrench589 · January 16, 2015

I would say that each microphone is exactly that, a microphone. A sensor. Turns sound energy into and electrical signal. No more, no less. All the noise compensating brains will be in a module somewhere else, not in the microphones. Putting the "smarts" in the microphone would be highly irregular, not to mention extremely expensive - why spend all that money to miniaturize all those electronics when there is lots of room elsewhere to build a larger module. No, the microphones are simply sensors. And normally, disconnecting a sensor does not shut down the module that is monitoring it. Sure, the module may detect a failed/missing sensor and produce an error code if the design so designed it in. Or not. My guess is that all you have done is removed 1 of the 3 input signals and the other 2 are still feeding sound to the ANC module and it is still outputting compensating sounds waves through the speakers/subwoofer.

Now, there may be some advantage to reducing the number of microphones. I would think that it would be extremely complicated to sense various signals from different locations and then output sounds from various other locations such that the sound waves are exactly 180 degrees out of phase at the right location at the right time, taking into account the different locations of he mics and the speakers and the exact distances and time it takes the sound to travel, and , and, and, etc etc. If the phasing/locations aren't perfect, the result could be an amplification of sound instead of cancelling. Or at least more sound then without ANC. So, did Bose do a good enough job of engineering the ANC brains to perfectly account for all the various locations, etc? Based on the quality of the music, I gotta doubt it! Lol! My gut feel is that ANC is a nice theory on paper and makes the nerds at Bose all excited, but to put it in practice in a motor vehicle at a reasonable price..... Well you know how that works out!

I taped over all three mics in ours about an hour ago and my wife is out driving it around this afternoon. Will let you know what she observed later on. One thing I noticed that bothers me is that the mic in the rear is in the center of the vehicle and the headliner is not attached at all in that location. It bounces around at the slightest of touch. I'm no expert on microphones, but I would think that if the mounting device for a microphone (the headliner in this case) is moving, it could create a false signal in the microphone. Heck, I'm sure that's why high quality studio mics are mounted on a flexible suspension system - to isolate them from all vibration in the mic stand. Imagine the center mic is getting bounded around mechanically by the bouncy headliner, generating a "false" signal in the microphone that the ANC then sees and outputs a sound to cancel. Except the original sound was actually there. And the cancelling sound has nothing to cancel so instead is heard by the occupants. Wouldn't that be a kicker!

We'll see how my tape works.

jasondenali15 · January 16, 2015

Well, after a 10 minute drive at a slow speed (less than 40), my ears were driving me nuts with the pressure!!! I called the dealer to reconnect whatever they disconnected on the passenger side for Monday. This made the situation much, much worse. Disconnecting that mic certainly was not the answer for my ride. 100%.

I give you guys a ton of credit for trying to come up with ideas. I am hopeful I can help. Is there any speed you want me to focus on while I still have it disconnected for your research?

I can tell you with absolute certainty the ANC is needed at the slower speeds. I feel like I just got done SCUBA diving. I am still trying to un-pop my ears as I type this.

Edited January 16, 2015 by jasondenali15

The Zip · January 16, 2015

wrench589 - taping is crude, but only part of the process. You would have to know if 20sierra14 taped the mic with or without the grille in-place and you would also have to fill the mic-well with cotton to get to his point in the process. Without knowing that, whatever you did will just be additional data but may not provide data beyond what 20sierra14 provided.

jasondenall15 - Take off the grilles from the other mics and go for a drive and see what happens. Also, don't drive anywhere but turn on XM (tune a few channels) and see what happens with that.

Keep in mind, ANC application has too many dynamics for you and I, the goal should be to take 20sierra14's concept to another level, he said the problem stopped.

20Sierra14 · January 16, 2015

Well, after a 10 minute drive at a slow speed (less than 40), my ears were driving me nuts with the pressure!!! I called the dealer to reconnect whatever they disconnected on the passenger side for Monday. This made the situation much, much worse. Disconnecting that mic certainly was not the answer for my ride. 100%.

You answered your own issue... This right there PROVES that it's the ANC "system" creating the pressure.. The tech did whatever he was doing to the ANC system (one mic only??) and that made the situation worse.. This happen to me when I pulled the "AMP" fuse to test the 1st idea we had.. The pressure was MUCH worse during the ride w/ the fuse pulled!

Keep in mind, I have zero "buffeting" sound in our Denali, only pressure. So folks hearing that noise only, I have no input for that...

The cotton ball test is very complicated... REMOVE THE GRILLE and stuff as many cotton balls in the opening as possible! Haha! Refer back to my pic of the actual microphone and you'll see that "o-ring" foam piece.. Take half a cotton ball and stuff inside that o-ring and then fill the entire opening w/ 2 more full cotton balls.. Tape it up, then take it for a spin!!

Post your findings!

Edited January 16, 2015 by 20Sierra14

The Zip · January 16, 2015

Whoa, slow down 20sierra14. This thread is transitioning from Research to Development. You placing cotton in the mic-well of your vehicle is one thing, telling others to do the same is another. We don't won't to jump out the pan and into the fire. Cotton in proximity to electrical connections is like tinder and a spark.

I do like the concept, although I didn't factor this in when I was in my developmental stage. Under the headliner is a spider of electrical connections, questions should answered before someone attempt to place cotton near those electrical connections.

Does the mic-well have finite edges or is the mic-well in an enclosed cup? This would eliminate external wires from coming in contact with the cotton

Does the mic connection emit a current?

If the mic connection emits a current, what is the impact exposed to cotton?

When someone is confident the cotton is isolated, then you may want to go with 20sierra14's suggestion. Buffetting is one thing, truck burning up is another. Thus, jumping out the pan and into the fire (literally)

Edited January 16, 2015 by The Zip

Wrench589 · January 16, 2015

My wife says that she heard absolutely no buffeting noise today! And, it was quite bad yesterday she said. Now, we gave seen it come and go over the last few weeks. Seemed that road surface condition plays a role in it. But, very encouraged by today's result.

FYI, all I did was cut a 1" square out of an old (thick) towel I had in a bag of rags. Then, I taped it over the microphone grill with wide masking tape. Did same to all three. Easy peasy.

Curious about something 20Sierra14 said. Pulling the fuse to the amp should cut all power to the audio amp. Thus, the ANC system would be rendered completely inoperative. No power, no sound output from the speakers. Now, there could be an exception if the subwoofer is power separately (as many home theatre subs are), but the is no fuse labelled for it. And, the subwoofer output is from the same amp at the back of the vehicle that all the other speakers are connected to. So, it looks like the subwoofer is not a powered one. So back to my premise, that pulling the fuse should disable the ANC completely. So, if pulling the fuse does not solve the problem, I have a hard time believing the ANC is the root cause.

20Sierra14 · January 17, 2015

Whoa, slow down 20sierra14. This thread is transitioning from Research to Development. You placing cotton in the mic-well of your vehicle is one thing, telling others to do the same is another. We don't won't to jump out the pan and into the fire. Cotton in proximity to electrical connections is like tinder and a spark.

I do like the concept, although I didn't factor this in when I was in my developmental stage. Under the headliner is a spider of electrical connections, questions should answered before someone attempt to place cotton near those electrical connections.

Does the mic-well have finite edges or is the mic-well in an enclosed cup? This would eliminate external wires from coming in contact with the cotton

Does the mic connection emit a current?

If the mic connection emits a current, what is the impact exposed to cotton?

When someone is confident the cotton is isolated, then you may want to go with 20sierra14's suggestion. Buffetting is one thing, truck burning up is another. Thus, jumping out the pan and into the fire (literally)

Well, I'm not GM telling customers to do this as their "fix" for the problem indefinitely. I simply need someone to be the 2nd "test" to the theory. From my pictures posted, there aren't any exposed electrical wires of any kind in the opening that the grille covers. Heck, my entire home theater's speakers have cotton stuffed inside the speaker cabinet -- and theres a lot more power running to those than these mics would ever have.

Wrench -- I may be wrong, but I think there is a 2nd AMP that handles the ANC. But that leads to the next question.. Why in the world would the pressure be worse w/ the stereo's systems AMP fuse pulled...??

Just another example of it leading back to ANC trying to compensate "something"...

Wrench589 · January 17, 2015

Well, based on what my wife tells me, I can corroborate 20Sierra14's result. That make two of us, buddy!

Now, if there is a second amp things are complicated. Any thoughts on which fuse circuit it gets power from?

Assuming only one amp, I do have a theory that could explain what you observed. Bear with me on this.... Let's assume that there are at least two forms of Noise Cancelling occurring. One that is based on measured noise from the microphones, and one based on pre-programmed sounds to cancel "known" known engine noise. Let's further assume that engine cancelling portion works pretty good, but the microphone based stuff isn't so great. Now, pull the fuse and all noise cancelling is turned off. Engine noise creates terrible noise. Sounds bad. Fuse in, microphones muffled - engine noise still cancelled, and microphone noise cancelling defeated.

Just a theory. Not saying it's a good one.

jl449 · January 17, 2015

Heck, my entire home theater's speakers have cotton stuffed inside the speaker cabinet -- and theres a lot more power running to those than these mics would ever have.

It's polyfill -- use it in subwoofer/speaker enclosures.. You do have a point.. there is a lot more power running thru those speakers than the tiny mics!! LOL

My Denali is expected to be delivered in early Feb... I hope I don't have to install this headliner when I get my 70+K SUV!!

Edited January 17, 2015 by jl449