Whining- Motor/gearbox noise

Cocijo

Cocijo

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Do any of you technical people know exactly what causes the light whining noise (which is normal) on our cars? Is it the electric motor bearings? Is it the transfer gears within the electric drive transmission system? I know that a lot of electric motors these days are near silent.
 
I think you may be talking about the artificial sound they have added to alert pedestrians that you are driving up behind them. I know some EVs have different sounds to choose from or the option to deactivate it entirely. Not MG.
I do believe it's required by law in some countries.
 
Extract from reddit.com/r/askscience


"Good question, actually most of the whine does not come exactly from the motor, but it comes from all the mechanical parts that connect the rotor to the gearbox and then to the wheels. In the case of racing cars or toy cars theres a lot of noise coming from the spur gears. Meanwhile in a tesla they use more silent helical gears.

But in some cases, the frequency of the signal they may use to power the motor can indeed generate noise, just like the humming from the 60hz in a transformer, we can clearly hear when PWM signals go bellow ~15khz. This phenomenon is called electromagnetically excited acoustic noise and vibration."
 
2of3 said:
I know some EVs have different sounds to choose from or the option to deactivate it entirely. Not MG.
Click to expand...
I though on the ZS you could turn off the alert in infotainment screen? It defaults to on when you start a new journey. I don't think the 5 has this facility though.
 
I’m not referring to the pedestrian alert. I think that defaults to on - at each journey. It is the general whining of the motor/drivetrain I’m asking about - curious about what generates the noises.
 
I can only hear the pedestrian alert on mine, but then I suffer from Industrial deafness, thanks to a former noisy job back in the 70s, where I have a loss of hearing certain frequencies.
 
The pedestrian alert turns back on every time you restart the car (unless you unplug the speaker like myself and others have)

I know what you mean about the motor whine. Sounds like a milk float sometimes.
 
Cocijo said:
I’m not referring to the pedestrian alert. I think that defaults to on - at each journey. It is the general whining of the motor/drivetrain I’m asking about - curious about what generates the noises.
Click to expand...
I think the slight whine that @Cocijo is referring too, can be produced when the car is travelling at between 27 - 28 Mph.
The whine can be heard when lightly feathering the "GO" pedal at this speed.
You can produce or loose the whine by lifting back, or applying pressure to the pedal.
It it hard to produce and can only be heard when everything is switched off in the car.
The Demo car I drove back in Nov 2019 was the same.
My brother has a ZS EV that is only about 3 months old and only covered 1,000 miles, and it does the very same thing.
For some reason, it only produces this slight whine at this speed and no other as best as I can tell.
I have no idea what is producing the noise, sorry !.
 
There is another component to the noise. It’s caused by the very slight noise made by the “gearbox”. What gearbox you say! It’s not a full gearbox as in an ICE car and can be seen as the combined final drive & differential which is used to reduce the motor speed down to axle speed and also make the car go round corners. Normal ICE cars also make the noise, but its masked by the noise of the engine and exhaust which swamps the small amount of noise made as I’ve described.

The noise comes from the metal on metal contact between the teeth on the gears. It’s very slight and partly masked by oil. Gearboxes are highly efficient, but not quite 100%, with the very slight losses manifesting in the form of the gearbox heating up and slight noise that’s made. The noise tends to be worse when under high power (foot down), and better when on a light throttle as that’s reducing the amount of power being transferred between the teeth. The same thing applies to the electrical “noise” referred to earlier in the post - so they essentially combine to produce a characteristic noise to a particular vehicle.

As a matter of interest, there was a new form of electric motor racing featured on the news earlier - extreme E. See if you can find something on YouTube about that and you will see and hear, exactly what I mean. Sounds a bit like our cars, but not exactly the same and somewhat louder.

Hope this somewhat anal explanation helps 😎
 
In fact, there’s a whole discipline within the automotive industry, it’s called “NVH”, which stands for Noise, Vibration & Harshness. When I say discipline, it’s actually the removal of these. An extreme example is that awful resonance you get on a bus at slow speed sometimes- it’s actually an effect of resonance of the “natural frequencies“ of the various component parts ...... For further info, please Google NVH 👍
 
Lincs Robert said:
In fact, there’s a whole discipline within the automotive industry, it’s called “NVH”, which stands for Noise, Vibration & Harshness. When I say discipline, it’s actually the removal of these. An extreme example is that awful resonance you get on a bus at slow speed sometimes- it’s actually an effect of resonance of the “natural frequencies“ of the various component parts ...... For further info, please Google NVH 👍
Click to expand...
probably the best answer as for mine it only produces it under near 0 throttle. If i have very light regen or light acceleration the tone slightly changes but If i put a load on it the noise dissappears.
Strangely when I had a courtesy EV for the day, it did not produce the noise... just luck of the draw I guess.
 
Cocijo said:
I’m not referring to the pedestrian alert. I think that defaults to on - at each journey. It is the general whining of the motor/drivetrain I’m asking about - curious about what generates the noises.
Click to expand...
I had my car in for the latest BMS update yesterday due to the failure of the previous update in Nov. That in itself is a dif story which I will put in another post. I was given a new Kia Soul EV as a courtesy car for the time my car was in for the updates. Now the Soul does have a few features we do not have on our MG ZS, it has more room inside, in the front anyway, it is quicker, the ride is firmer, the one aspect relevant here is it is not more quiet than the MG, my wife and myself could not honestly state that the KIA was more quiet than our MG, I would have to say there was no significant difference. The Dealer knows I have been interested in an E Niro for a second car and has tried to sway me towards the Soul. Simply because it is easier to supply apparently. Yesterday’s drive hasn’t changed my mind on the Soul. I still wouldn’t have it sitting on my driveway, Postman Pat might, but I wouldn’t.
 
I think that some of the noise is also caused by the mating of the gears under load and on overrun. My car is noisier on overrun than when under load.
 
Not me. I don’t find the car that noisy really. It’s subjective I know but I don’t think it’s a particularly unrefined car for the bracket.
 
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