2015 YUKON NOISE IN CABIN

FogDucker · October 6, 2015

I used a similar sound analyzer and did dozens of different tests, on my vehicle as well as several rentals. Pretty sure the buffeting is just under 30 hz. But there is a fair bit of noise at all frequencies, so pretty hard to isolate. I also did a rough calculation of what frequencies fundamental standing waves would resonate at in the XL version and came up with higher first order frequencies then the 29 hz.

If you want to get a sense of what frequency the buffeting is, you could also do what I did to verify the microphone in my tablet can actually sense such low frequencies. I down loaded a frequency generator app. Now, the speaker in the tablet won't output much under about 100 hz, so I connected the headphone jack to my home theatre subwoofer. And guess what? 30 hz sounds EXACTLY like the buffeting in my Yukon.

So now what? I shared this info with the service manager at my dealership and I could tell this was WAY of his head by the deer-in-headlights look.

Also, I sat I the back of mine several times and to be honest, the buffeting is much less noticeable. Seems the drivers seat is the worst place to sit. So, that of course makes sense with low frequency sounds as they will hacpve a very long wavelength and hence, the nodes and antinodes will be quite far apart and the amplitude the ear hears will vary greatly with where you are relative to them along the wave. For example, the wavelength of a sound wave in air (at 20C) at 29 hz is approx 1.2 meters.

Interesting. The tricky thing about that frequency is that it's difficult to locate the source. It doesn't matter where you put the subwoofer in your living room, except to the ladies of the house. If you're right about the wavelength, this means that the sound is not in the rear [hatch] area, rather more close to the second row seats. I'm sure we'd find body mounts and suspension components there too. I have only heard "the boom" from the front seats, but then again, have never been for a ride in the 2nd or 3rd row. That's an important clue.

The other thing I observed that is very important is the buffeting actually "phases" in and out. This is typically a beat phenomenon and could be caused by some kind of interference between multiple waves in the cabin. Or, the vibration that is caused the buffeting that is phasing in and out. Has anyone else observed the phasing in and out?

Yes! It's gradual. Fades in, fades out. Road conditions and throttle [with or without AFM] don't seem to play a role. Speed does. ~65km/h [~40m/h] and ~120km/h [~70m/h] seems to produce the boom on most road surfaces, most of the time.

Recent posts on the pickup thread on this site are quite disappointing. Someone posted that the body mounts are involved in the excessive transmission of vibration but according to someone at GM, GM will NOT be changing them because to do so would mean re-doing all the government crash testing and GM is not going to do that. Now, I did a bunch of research a while back and I am pretty sure that a change to the body mounts will "detune" the entire body/frame structure and possibly resolve this whole thing. But based on what I read over there, I have lost all hope GM will be doing that. Heck, I even recorded all the body mount parts numbers from the 2015 parts manual to track any changes that get made. Now, seems less likely to happen.

If body mounts were the root cause, wouldn't *all* 2015/2016s would have "the boom"? Maybe it's a bad batch of body mounts, other parts or assembly issues? What parts could be responsible for generating high, medium or no boom at all?

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Marc

FogDucker · October 6, 2015

The boom could be a body-on-frame related issue or hatch related as reported on teslamotorclub.com:

This was one of the first problems I reported to Tesla. On my drive home from the factory I too noticed the horrible "pressure buffeting" when all of the windows and sunroof were closed. I tried several experiments to see if I lowered the windows slightly or opened the sunroof if it would go away. It didn't. After discussing it with the LA service center and them with corporate they determined this is a known issue and is actually caused by rear hatch. If you open the rear hatch you will find two thumb screw type rubber dampers on each side of the hatch by the edge (not the solid plates they press against on the car itself). If the screws are not far enough out the hatch acts as a large speaker bouncing up and down as you drive over uneven roads creating this uncomfortable pressure feeling. Adjust them out far enough so the hatch closes tightly but not too far where the automatic closer will not shut because there is too much pressure. This adjustment, in combination with the rear parcel shelf to absorb vibration, greatly reduces the pressure buffeting problem.

If you're not feeling anything you are fine. It kind of feels like sticking your head inside a bass drum and having someone lightly lap the head of the drum. It's feels kind of like a slight change in air pressure in you ears accompanied by a low frequency rumble.

The sound comes from the tires and the suspension usually, but the pressure feeling is coming from the movement of the rear hatch acting like a big sub-woofer. So if you don't have that sensation, your hatch is probably adjusted so there isn't enough flex to cause the acoustic effect.

It happened at all speeds in my car. I could be going slow over road bumps, or going quickly at highway speeds.

RC45 · October 6, 2015

Is this ANC standard in all the trucks? If so, where are the mics and how would this work if the sound system was removed or replaced with a non-OEM one?

Wrench589 · October 7, 2015

Is this ANC standard in all the trucks? If so, where are the mics and how would this work if the sound system was removed or replaced with a non-OEM one?

As far as I understand, the "ANC" is only on the upper models - Denali and LTZ. This is evident by the fact that those models have the a total of 4 microphones in the headliner; one for handsfree and three for the ANC. The other trim levels only have the one handsfree microphone.

I did a test with mine by completely disabling the ANC by removing the main fuse that powers the entire audio system. The buffeting did not change. I did hear more road noise and wind noise, though, so told me the ANC was doing something, and I did disable it for the test.

Now, it is entirely possible that the ANC is doing nothing to combat the buffeting sound. It is possible it is not even tuned to respond to such low frequencies. I have no idea.

FogDucker · October 7, 2015

I experimented with the adjustable stops located halfway down the hatch. Tried fully screwed, half screwed [close to stock] and nearly fully extended - no change. I also tried with the 2nd row [bench] folded and flipped - no change. Next is to poke around with the "fold flat" 3rd row and rear storage bin.

@RC45: ANC is not standard on all trucks. The boom was reported on trucks with and without ANC. Those who did have it disabled it by pulling the fuse. No change.

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Marc

Edited October 7, 2015 by FogDucker

Wrench589 · October 7, 2015

Interesting. The tricky thing about that frequency is that it's difficult to locate the source. It doesn't matter where you put the subwoofer in your living room, except to the ladies of the house. If you're right about the wavelength, this means that the sound is not in the rear [hatch] area, rather more close to the second row seats. I'm sure we'd find body mounts and suspension components there too. I have only heard "the boom" from the front seats, but then again, have never been for a ride in the 2nd or 3rd row. That's an important clue.

Yes! It's gradual. Fades in, fades out. Road conditions and throttle [with or without AFM] don't seem to play a role. Speed does. ~65km/h [~40m/h] and ~120km/h [~70m/h] seems to produce the boom on most road surfaces, most of the time.

If body mounts were the root cause, wouldn't *all* 2015/2016s would have "the boom"? Maybe it's a bad batch of body mounts, other parts or assembly issues? What parts could be responsible for generating high, medium or no boom at all?

--

Marc

Exactly. In fact, the source could be anywhere in the cabin.

Most interesting. Mine is almost at the identical speeds.

I still believe all of the vehicle are doing it. Some worse then others, possibly due to difference in tire RFV or road surface, or other factors. And of course, differences in driver hearing sensitivities. But of then3 or 4 rentals I've had, they all did it to some degree.

Here is one more test for you do try, Marc. Sit in one of the second row seats, with the vehicle not running and in a quiet environment. Open the door beside you, and swing it open and close several times without fully closing it. Tell me what you hear every time the door goes through the detents that are in the hinge mechanism that help,hold it partially open.

Edited October 7, 2015 by Wrench589

FogDucker · October 7, 2015

Here is one more test for you do try, Marc. Sit in one of the second row seats, with the vehicle not running and in a quiet environment. Open the door beside you, and swing it open and close several times without fully closing it. Tell me what you hear every time the door goes through the detents that are in the hinge mechanism that help,hold it partially open.

It does have a similar tone to "the boom". Kinda like a rubber mallet on metal. Not the same sound as driving slowly over a bump or the 65kph/120kph fluttering boom.

I just called my neighbour, asked him if he'd like to test drive a 2015i Yukon at ~65km/h. He agreed and drove while I sat in all 7 passenger seats [2nd row bench]. Observations:

We started with me sitting in the front passenger seat for driver ear training. It wasn't immediately obvious to him, but when I pointed it out, he could identify "the boom". He could also hear it when driving over bumps at lower speeds [as if someone flicked a 12" woofer with their finger]. Training complete, in the back I went.
I was unable to hear "the boom" in either the 2nd or 3rd row. I tried every combination of seats up/down/folded. I even pulled back some of the insulation from under the 2nd row to feel for vibration on the metal floor. I lied flat and put my head down in the footwells - no boom.
Oddly, he wasn't able to consistently reproduce "the boom", but the odd time he did, I thought I could feel vibration in the 2nd and 3rd row. I couldn't isolate it.
I can rule out the hatch and rear storage. I literally had my ear to the floor and trying pressing/banging on panels.
The exhaust note / reverb sounds a bit different in the back seats. It can be heard more clearly. [LOVE IT!]
Outside temperature: 15C/59F

For those who have "the boom", are you able to hear it from the 2nd or 3rd rows? Does it sound different? Can you feel any vibration?

--

Marc

ajs800 · October 7, 2015

It does have a similar tone to "the boom". Kinda like a rubber mallet on metal. Not the same sound as driving slowly over a bump or the 65kph/120kph fluttering boom.

I just called my neighbour, asked him if he'd like to test drive a 2015i Yukon at ~65km/h. He agreed and drove while I sat in all 7 passenger seats [2nd row bench]. Observations:

We started with me sitting in the front passenger seat for driver ear training. It wasn't immediately obvious to him, but when I pointed it out, he could identify "the boom". He could also hear it when driving over bumps at lower speeds [as if someone flicked a 12" woofer with their finger]. Training complete, in the back I went.

I was unable to hear "the boom" in either the 2nd or 3rd row. I tried every combination of seats up/down/folded. I even pulled back some of the insulation from under the 2nd row to feel for vibration on the metal floor. I lied flat and put my head down in the footwells - no boom.

Oddly, he wasn't able to consistently reproduce "the boom", but the odd time he did, I thought I could feel vibration in the 2nd and 3rd row. I couldn't isolate it.

I can rule out the hatch and rear storage. I literally had my ear to the floor and trying pressing/banging on panels.

The exhaust note / reverb sounds a bit different in the back seats. It can be heard more clearly. [LOVE IT!]

Outside temperature: 15C/59F

For those who have "the boom", are you able to hear it from the 2nd or 3rd rows? Does it sound different? Can you feel any vibration?

--

Marc

Marc - Did you notice the buffeting/pressure issue when sitting in the back seats?

Also, the buffeting pressure feeling with my 15 XL SLT is at its worst around 40 and 70mph as well.

Edited October 7, 2015 by ajs800

FogDucker · October 7, 2015

Marc - Did you notice the buffeting/pressure issue when sitting in the back seats?

Also, the buffeting pressure feeling with my 15 XL SLT is at its worst around 40 and 70mph as well.

No, I did not. I'm not sure what that means or if it's consistent with what others are experiencing.

I'll be driving approximately 1000km over the next week, mostly highway, half of it with a trailer. I'll train my son for "the boom" and will gather some more observations.

--

Marc

The Zip · October 7, 2015

As far as I understand, the "ANC" is only on the upper models - Denali and LTZ. This is evident by the fact that those models have the a total of 4 microphones in the headliner; one for handsfree and three for the ANC. The other trim levels only have the one handsfree microphone.

I did a test with mine by completely disabling the ANC by removing the main fuse that powers the entire audio system. The buffeting did not change. I did hear more road noise and wind noise, though, so told me the ANC was doing something, and I did disable it for the test.

Don't know if I am following this, the Tahoe LS, LT and the Yukon are the least expensive GM Fullsize SUVs. But if anyone of those trucks were taken to the dealer and asked what could they mod, the only thing that would be a problem would probably be the 6.2 and the Mag Ride, everything else is pretty much plug and play. Which would make these trucks the same. If that's the case all should have ANC. If not, based on your test the least expensive models should therefore have crazy road and wind noise. I have a LT, my RPO code says my truck came with ANC and I have no road or wind noise.

The Zip · October 7, 2015

I still stay the shocks are one of the leading causes of this problem.

If this is what you believe, why not spend the money and get the best shocks on the market?

yahtzee · October 7, 2015

I took my first legitimate trip with my '16 XL Densli yesterday. Buffeting from 40-78mph. Actually improves above 78mph. Interesting note: my vibration issue that went away is back BUT only around 75-77mph. It also goes away above 78mph but is not present below ~70mph.

At 80+, she hummed right along.

Coming into town after exiting interstate popped the tranny into is lovely sounding 12th gear. Annoying. Took my parents out to dinner and had my mom drive it home. She was so enamored with its size that she didn't even hear the buffeting - until I said "listen...doesn't it sound like a window is cracked? Do you hear it?" She heard it.

Overall, I enjoyed the truck but I'm still puzzled why GM hasn't found a fix for these issues.

Regarding my follow up to the news outlets, auto rags and publications.....I heard back from one editor who copied a guy with ties to GM. Following up with him again today as well as pinging every single contact I reached out to last week. The Facebook group is small (growing) but who cares? Just another means to show GM the effort we're putting in to gain more attention.

FogDucker · October 7, 2015

@yahtzee: To be clear, "she hummed right along" means no buffetting/vibration, right? Did anybody in the 2nd or 3rd rows hear "the boom"?

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Marc

ajs800 · October 7, 2015

Marc- Do you not experience the buffeting in your denali? I know I'm late to the party as I have only had my 15 for a month but it seems as though there are two main cabin issues...

1. Buffeting (which I believe has been present in all models from base to denali/ltz)

2. The "boom" sound which seems to be isolated to the denali/ltz with ANC.

Is this accurate? I don't seem to have the Boom sound issue with my SLT....it's actually very quiet with only the annoying and sickening(literally) buffeting/pressure problem.

Edited October 7, 2015 by ajs800