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Wow this is a REALLY interesting article. Again, EV's are different beasts entirely. For the problems described in this thread the most intriguing line from the Results section is:

"In the case of the Audi E-tron, thanks to the DoE, it is clear that the two front bushes of the electric drive have the greatest impact".

I wonder if there is some manufacturing variability or defect.
 

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2019 e-tron prestige
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Yes! This has got to be the problem.

From TSB 40 20 03 2058489/2 March 12, 2020:
"Customer states: "They can hear rumbling, squeaking, creaking or similar noises from the front end when driving on uneven roads. The noises can possibly be heard and felt in the foot well or behind the dash panel."

Their service guideline (for the above complaint) was to "replace the hydro-bush on the guide link in pairs." It's unclear that this TSB is directed towards body boom though.
I have to reiterate that I've never felt this sensation in any car before, including many other dual motor EVs.
 

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Possibly so! This type of harmonic suppression might already be in use. Looking at Fig 7, though, this modeling seems to assume a stable body and wheel arrangement. The problem people experience generally is on rough and/or uneven surfaces. Even the stable situation would require a good deal of computing power, so imagine the increased complexity and required response times for real time compensation if you start throwing in random body and wheel motions! I can see why the bushes would be so important for this to isolate the drivetrain from the body and visa versa. I recall earlier in the year Audi announced improvements to the car that added about 10 miles to the range. It had to do with modifications to the motor that improved efficiency and rolling distance--ie, less friction. Audi incorporated this into late 2019 models, but no retrofit. I wonder if that also addresses some of this booming issue.

Still, everyone doesn't seem to experience this, so there must be some combination that minmizes booming to acceptable levels. EV's motors are just too quiet!
 

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Discussion Starter · #25 ·
I don't believe TSB 40 20 03 2058489/2 is related to the boom sensation or at least it did not fix the problem on this thread:


From the thread:

WildBTK "I had this TSB applied to my eTron. It did not fully solve the suspension clunking on the front end. My post was about the rear suspension booming sound going over some bumps. It's hard to describe and will be nearly impossible to record."
 

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Discussion Starter · #26 ·
Still, everyone doesn't seem to experience this, so there must be some combination that minmizes booming to acceptable levels. EV's motors are just too quiet!
Is it possible it may be a combination of some owners not being aware of, or as susceptible to, the 'boom', combined with varying levels of 'boom' within e-trons? What concerns me more is a lack of awareness or acknowledgment from Audi, let alone a fix.
 

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Is it possible it may be a combination of some owners not being aware of, or as susceptible to, the 'boom', combined with varying levels of 'boom' within e-trons? What concerns me more is a lack of awareness or acknowledgment from Audi, let alone a fix.
I would think at least this first reference to controlling "body boom" would be relevant:

Have you been able to demonstrate it for your Dealer?
 

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A test tone should key the listener in to what we're hearing. I will have to try playing it through the e-tron speaker system to see if it can accurately reproduce the sound.

35 Hz test tone (warning: be careful, start at very low volume)

For me, this approximate frequency occurs in the car, in a quick pulsating manner.
 

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A test tone should key the listener in to what we're hearing. I will have to try playing it through the e-tron speaker system to see if it can accurately reproduce the sound.

35 Hz test tone (warning: be careful, start at very low volume)

For me, this approximate frequency occurs in the car, in a quick pulsating manner.

Wow, I played that back on my desktop, which has a decent sound system. That low drone is really annoying, even got some sense of light pressure in the ears! I can only imagine how annoying it would be rapidly pusating! I most definitely do not hear that in my car. It almost sounds like an electrical hum, like from a transfomer.
 

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Yep! It feels like being knocked on the head with a fist. My ears also pop frequently on rough roads.

Hmm, maybe the motors should be inspected as well.

I’m glad to hear you’re not experiencing this in your car. That suggests it should be fixable.
 

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Discussion Starter · #32 ·
@polyphonic my Audi dealer is saying there is no fault with the car. Have you booked your car in to your Audi dealer for inspection? I'm interested to see whether they can experience and acknowledge the issue.
 

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@Nic99 that’s unfortunate. Did you see my post on Audiworld with the audio examples? The mock-up is audible through the car’s stereo system. That may be useful in getting the point across.

Mine is in service now for some other items, but I demonstrated the booming noise for them to investigate. (And of course, the new ICE loaner car does not make this sound)
 

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Discussion Starter · #34 ·
My car was with the dealer a couple of weeks ago, prior to your idea of a demonstrable noise frequency and due to Covid restrictions I was unable to demonstrate the problem first hand.

Please do update us on how the Audi dealer progresses with the booming noise investigation.
 

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My car has the hydro-bush TSB, but unfortunately it came back 'normal.' This is disappointing since NVH is a major highlight of the vehicle.
 

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Everyone who have this issue, please check the spare tire compartment. I found that my spare tire is not screw down completely. This might solve the issue.
 

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I experience the same with a brand new e-Tron SB 55. Chaning tires pressure has little to none impact on the rumbling. Body boom as described in audiworld forum and the scientific paper has been improved (!!!) however when going over 110km/h the car exhibits rumbling in the low frequency range.

I believe it is more common with recent Audi cars with air suspension. My Audi A6 (2018 C8) does exhibit the same rumbling but is much less loud than in the e-Tron. Driving other Audi cars with normal suspension they do not exhibit the rumbling (same A6 but with normal suspension or Audi Q5). So only to blame the EV drive train and some buhsings is i think a far stretch from the paper. Audi has an issue with the air suspension in my opinion and not particular with the ev drive train.
 

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Had some booming from my e-tron 50 in All-road mode this morning, driving along a failry smooth road in wet but drying conditions. Similar to the 35hz noise but only happening when hitting minor divots in the road. Its a road I drive most days, but I rarely use All-road, normally dynamic or comfort which don't bring out this noise/sensation. Posting this in case it helps anyone with their investigations.
 

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Body boom as described in audiworld forum and the scientific paper has been improved (!!!) however when going over 110km/h the car exhibits rumbling in the low frequency range.
That is interesting, since it appears to be more prevalent at lower speeds in mine. over 110 km/h, I might hear it once every several seconds, instead of several per second at 45 km/h. I am planning on trying a measurement mic for infrasonic frequencies (below 20 hz). Still very much bothered by this issue, but stuck with the car.

Had some booming from my e-tron 50 in All-road mode this morning, driving along a failry smooth road in wet but drying conditions. Similar to the 35hz noise but only happening when hitting minor divots in the road. Its a road I drive most days, but I rarely use All-road, normally dynamic or comfort which don't bring out this noise/sensation. Posting this in case it helps anyone with their investigations.
AFAIK the dampers are the same, and it's just a ride height adjustment? Thanks for the info though -- will have to systematically try all of the suspension settings on the same road stretch, just to see. I use auto most of the time, fwiw.
 
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