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Concerning Motor Noise

I have noticed a noise that I believe is related to the motor. I have read about highway cabin noise, the high-pitched whine with acceleration and AC related noise, but the noise I am hearing is different. I searched the forums and found about six other users with reports of a similar noise at http://www.teslamotors.com/forum/forums/firmware-44. I addressed my concerns in that thread, but the thread was created to discuss software, so I decided to start a new thread to see if I can find some answers.

The noise typically occurs when driving faster than 30 or 40 MPH and definitely while I am on the highway at higher speeds (60 MPH). The noise becomes audible as soon as I push the accelerator and goes away as soon as I take my foot off the accelerator. It sounds like a low pitch humming noise or a buzzing noise and while it's hard to pinpoint, it sounds like it is coming from the back of the car.

I brought it in to my local service center and left it there for a day. They drove my car and other cars they had on hand. They noticed the sound in my car and not in the others. The best explanation they could offer me was that they thought it was normal, and perhaps it was part of the "break-in" of the car. They added that if it is actually an abnormal noise, the sound should get louder and louder over time. I'd rather not wait for a problem to get worse, which is why I have been searching the forums. One user in the aforementioned thread apparently had the same problem and had it "fixed" by a service center. But, the problem's explanation and the fix are still unclear.

I am not 100% sure, but I don't believe the sound was there when I first got the car in February of this year. I started noticing it a few weeks ago. Has anyone else noticed this? If so, is there an explanation and/or a fix?

Thanks in advance.

Do you have the AM radio on when this noise occurs? AM frequencies are very susceptible to interference from the electronics in the car. I know I get plenty of crossover noise whenever I have an AM station tuned in, so the noise is coming from the speakers in my case.

I have a similar problem except mine sounds like a high pitched electronic whine. . Again it only appends under moderate to heavy acceleration.

The sound comes from the driver side rear and It happens even if the radio is off or muted.

I asked at the service center and they said that it's normal. But I don't agree.

Mine is not related to AM radio and it's not the high-pitched whine that has been associated with acceleration- although I do have that as well. This is a different noise.

If your car does it and the others at the service center do not--they need to keep digging.

I haven't heard of, nor read in the "manual", anything about a break-in period.

Drive it like you stole it from day 1.

I have an S85 and took delivery in March. After about 1000 miles, I got upgraded to 4.3. The next day, I got upgraded to 4.4. At about the same time I started hearing the same noise that you describe - humming noised that started when I went above 65 and seemed to be coming from the back of the car. I spoke to a tesla service rep and they told me that they'd never heard of this problem before. After exchanging several voicemails to schedule a visit to the Meno service center, the noise went away. I can still hear a faint humming when I go about 65, but it's not as noticeable as before.

I have the same sound however I don't believe it is linked to a software update sd I have had 3+ updates with the noise remaining. My last explanation was that it was the differential. I have 10k miles on the car and the noise has not gotten better or worse, most noticeable at freeway speeds. I do not have an answer for what it is but I do not think it is software issue.

Hmmm, low pitched humming noise coming from the back. It sounds like we may have the same noise. To me it sounds and behaves like gear noise from the transmission. It's quiet on deceleration and "float" but the moment there is power to the wheels.....Hmmm.
I only recently started to notice the sound (@6500 mi.). If it gets louder I'll have it checked out.

This could be a pain to find. My Lexus had a wind noise problem that took them 2 years to solve (and was not retrofitted).

Is it possible your hearing is better than most? I'm sure many of us have loss a bit of the high-end, and the sound may be in all cars, but some of us can't hear it. Even the techs might not hear it.

I also have thick carpets on all the floors and the rear area. It might dampen the sound, but I don't remember any similar sound when I first got the MS and didn't have the carpets.

Lastly, it may be an audio system problem. Turn off the A/C and mute the audio. Have a passenger place their ear next to the door speaker and then next to the tweeter in the windshield pillar to see if they hear the sound from the amp. The amp might have a filtering problem and/or the motor electronics is not filtered enough and/or there is some kind of induction coupling of the frequencies.

Good luck! Anything you can do to isolate exactly where the sound is coming from will help the techs.

I have a sound like that when accelerating and to me, best described, as a very much muffled ICE acceleration sound. It sounds like if you're standing outside and hear a car accelerating rapidly far in the distance. My sound kicks in at about 40 kW of acceleration and tapers off as I reach a cruising speed. Doesn't really bother me and I assume it's something to do with the motor spinning up.

Thanks for the input. truebeliever and hfcolvin give good descriptions of what I am hearing. The noise persists with no AC and muted audio.

I have a feeling I will not find an easy answer, and while it probably shouldn't, it seems to bother me. It sounds almost like a bad muffler and I'm afraid it'll cramp my style when I'm trying to show the car off....

I'd also try another MS to see if you hear the same sounds. From the responses of other MS owners, it doesn't seem normal.

If it is unique to your car, it could be as minor as some sound-isolation material that is not in place or a tiny void that lets the outside/motor noise in. That doesn't mean it will be easy to find, but worth trying to locate.

I am really getting pissed off at Tesla for not acknowledging this issue.

I have the same problem with my car. Someone on TMC described it as a sound like when you stretch a balloon nozzle and it squeals. That's exactly the way it sounds.

Tesla knows what the problem is. It existed in their demos cars during the amped up events. When asked about the squeal I was told it was because these were alpha cars and the problem would be fixed.

I believe the motor controller is going into oscillation during heavy acceleration. Mine did it several times today going to work. I almost stopped by Fremont service to demonstrate but didn't have time. Then it did it again going home for every heavy acceleration I did for about 20 minutes. Then it stopped. This problem started several thousand miles after I got the car.

This is not normal. Do not let Tesla BS you. I have not been able to pin point the conditions, such as high or low battery voltage (it does it at both). Air conditioning seems to not make a difference.

Tesla please acknowledge this problem and fix it.

There is a soft whine in my car during heavy acceleration. According to a friend of mine who works at Tesla and is very familiar with the drivetrain it is due to the gears meshing. He said there's a trade-off between how quiet the gears are and how efficient they are using helical gears. The more teeth are engaged at any one time the quieter the gears but the greater the loss due to friction.

I agree that there is gear whine in the car. But if this problem was related to gear whine it would be there all the time and would change frequency with speed. This squeal I am referring to is abrupt, constant frequency and loud at high acceleration. And it sounds electronic, not mechanical.

Electronic sounds are very hard to localize, because the waveforms are identical, and the input from each ear is lacking in identifiable "wiggles" for the brain to match up.

Just to be clear - this post is not about the whine many people describe. This is the low, muffled noise that sounds like a buzzing or humming noise - almost like a bad muffler.

Mine seems to be getting louder. It really bothers me.

Brian H. I have been an electronics test engineer for 30 years. I've worked on high power electronics. The last was an HVAC system for a big rig that converts 12VDC to 300VDC at over a kilowatt to drive an air-conditioning compressor.

This noise the car makes is exactly the same noise that system made when it was unstable. It could result in the destruction of the power output stage.

I'm afraid that this could result in damage to the motor controller if allowed to continue too long. Then I could be stranded somewhere.

Today the car has not squealed on me. I'm beginning to suspect that it's temperature related.

@Michael39 - Impressive credentials. Certainly lends authority to your comments...

Yes, if the car is sending out audible distress signals, it behooves you to pay heed and respond.

I may be able to help, as I am a professional acoustical engineer and Board Certified in Noise Control. First, I do not have either the low-muffled sound or the high-pitched sound described by @jbrowdy and a few others here, respectively. Second, without experiencing these events, I can only offer some educated-guess work and a few troubleshooting ideas from experience in the science of noise control. Third, as noted by someone else, noise is very challenging to find, especially when structureborne in its origin. Fourth, I can't think of a fourth, so here I go:

RE: Low-muffled noise:
Since @jbrowdy's car has this noise and other cars driven by the service center guys do not, then clearly this is not normal and is not part of the "break-in", IMO. If this noise was present from day 1, and didn't just appear one day out of the blue, then either there is a defective part or there was a poor installation/assembly during the car's build. If it is a noise that began well after delivery, then see my comment below on the high-pitched squeal. Sorry I cannot be more specific with advise, but really without proper acoustical measurement, both sound pressure level and vibration analysis, it is difficult to be more narrow with a response. FWIW, the most difficult aspect of noise control is locating the origin or root-cause. Once the root-cause is identified, as you might expect, mitigation is often straightforward. Clearly, this problem has a solution, based on the fact not every Model S has this noise. I would keep pressing the service center to find and fix it - or get some professional help. If they need to bring in a skilled expert in acoustics, I can probably locate and recommend a name of someone, but I need to know where you're located. Alternatively, you could visit the National Council for Acoustical Consultants at www.NCAC.com, and there is a place on their website to find a local consultant.

RE: The High-pitched Squeal:
If the high-pitched noise of concern was not present when the car was new, but then begins to arise after time or after several thousand miles; then it is undoubtedly due to something failing (I know that states the obvious).

What I would recommend for the high-pitched squeal @Micheal39 describes is to have TM see if the motor controller is (1) failing or failed, and/or (2) it has worked itself loose due to road vibration after a few thousand miles. @Micheal, I think your suspicion of an oscillation in the motor makes sense, from my experience. Again, the same website listed above might provide the assistance TM needs to fix these noise-related concerns.

We all know from many threads about bad 12V batteries, which I had myself, that in my opinion, TM is most likely relying upon their suppliers for quality control, and TM needs to hold them accountable (zero defects). After all, replacing all these 12V batteries, and other components like door handles, charge ports, etc., has to be costing them money. I frankly do not know how TM controls quality, so these are just my suspicions, too.

Oh yeah, "fourth", please, please ensure this thread is private. good luck, keep us informed with updates, too. And for Brian H - I am at an airport gate waiting to board my plane, so in advance I apologize for my spelling and sentence structure, as my iPhone has this annoying auto-correct function that inserts what they want and not always what I meant to say.

Great stuff, Velo.

I'm in St. Louis, MO.

Safe travels ;)

advice

Auto-Error

If something is making unwanted noise, some part or parts are wearing out or coming loose or coming apart at an accelerated pace.

i too am hearing such a noise

Another analogy I would use is it sounds like a swarm of bees - but the pitch changes depending on how hard you push the accelerator.

I have the "hum" noise. I disagree with jbrowdy in that the PITCH changes only with the speed of the car. The AMPLITUDE or loudness of the hum increases with more pressure on accelerator. I would describe the sound more like what you hear when a monster truck (loud tires) is driving next to you (although not nearly that loud). It's best heard with the A/C and Radio off. I would also add that the noise occurs for me between 60 and 80 mph. I had my first Tesla Service appointment and demonstrated the noise to the lead technician (Nicholas in Phoenix). He was very interested and we went on a ride together. He listened closely to the back of the car. He had not noticed that particular hum before. My car is only 3 weeks old and the sound has probably been there since day 1. One thing I did was take out the rear "cover" (not the privacy cover) under the hatch to have that big well available for "stuff." Nicholas recommended reinstalling the cover. The cover is pretty thick and after reinstalling it, the noise level has gone down by 50% and is not nearly as noticeable. There is very little insulation for sound in the back and I believe more than likely it is a "normal" sound which could possibly be from the transmission or even the tires (I have 19" wheels in a 60 kWh MS). I would recommend reinstalling the rear hatch well cover. I would bet that the "jump seats" would help insulate the noise as well as the privacy cover. In a normal ICE car you would never hear a hum like this as the engine/transmission/road noise would drown it out and there is probably more insulation in an ICE car. For now I am going to monitor the noise per Tesla Service recommendation.

Itsele,
You may be correct. It may be a normal noise, and it is very possible I never noticed it before. If I had assurance that it is normal, I could live with it. It's not very loud. I just don't like the thought that something is possible abnormal.

I brought my car in twice for it, and then escalated the issue by calling Tesla. They want me to bring my car in again for the local service center to communicate with engineers. It's a pain to keep bringing the car in, so I am not sure how quickly I'll bring it in. If anyone has any additional information, please feel free to share.

Thanks.

Based on the descriptions from those that are hearing it, here is my guess:

Summary

Resonant vibration of loose magnetic coil windings under certain power demands.

Background

The power system contains inductors. These are windings of wire around a magnetic core - think of the wire around the nail experiment when you were a kid.

The power inverter (controls flow of power from the battery to the motor) has inductors in it.

The motor stator windings are also effectively the same class of structure. They are wire coils.

What happens to windings as you pulse current through them is that the magnetic field exerts a force on the coil each time you turn the current on and off.

Usually, these coils are laminated tight by winding tension and adhesives, so they don't move. Sometimes however, they can become loose through damage or defects.

When they are loose, they can jiggle when jolted by the surge of current through them. If that happens you can hear them buzz at a frequency related to how fast they are pulsed.

To increase acceleration, your Model S pulses the power through these coils at a tighter spacing (frequency and/or pulse width).

When the frequency matches the natural resonate frequency of the mechanical structure of those loose magnetic coils, they jiggle the most and sound the loudest.

Other things like the reduction can also show resonant vibration as a function of rpm. But you are hearing this on acceleration, not just at certs, but Based on when you hear this, I think this is the most likely reason.

The fix is to replace the loose coil structure, or apply damping adhesive to stops its vibration.

Accidentally hit send before finishing -

But you are hearing this specifically on acceleration, when current pulses are strongest, not just at a particular rpm when you are cruising. That's why pure mechanical vibration is less likely.

Based on when you hear this, I think loose coil windings are the most likely reason.

The fix is to replace the loose coil structure (inverter inductor or motor winding), or to apply damping adhesive to it to stop the vibration.

Missed this too -

"Other things like the reduction gear can also show resonant vibration as a function of rpm, but I think this is less likely."


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