Electric Motor Noise

Michigan Mike · #1 (**permalink**) 11-27-2009, 04:35 PM

I just did a search on "electric motor noise" but didn't find any related threads ...

Can someone please tell me why some electric motors are extremely noisy and others are quiet?
Which e-bike motors are quiet?
Thanks.

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deacon · #2 (**permalink**) 11-27-2009, 05:24 PM

You know thats a good question. I have three motors exactly alike and the all have a whine. High pitch whine for some reason except for today. Today I hooked a 350 controller to the 600 watt motor and it is as quiet as a mouse. Totally strange I know.

Michigan Mike · #3 (**permalink**) 11-27-2009, 05:45 PM

I was surprised to read in another thread how loud some ebike motors were. I think someone said his was louder than a gas motor. ?

professor · #4 (**permalink**) 11-27-2009, 05:46 PM

I was ready to buy an e-zip until I watched some videos on Youtube and a video comment about dogs barking a couple blocks away from the noise.
Some people aren't bothered but it would drive me nuts.
The Currie motors drive a straight cut gear reduction box and those gears scream. I would say, anything with gears would be noisy- I am using an electric scooter motor with a chain drive (thinking about friction drive instead) and it makes a little noise. Don't know much about the hubmotors.

Michigan Mike · #5 (**permalink**) 11-27-2009, 06:01 PM

That makes sense Professor ... about the gear noise.

deacon · #6 (**permalink**) 11-27-2009, 07:03 PM

I have a hub motor stored in the shop. It was fine when I got it but I had to replace the controller an now it sounds like it is going to lock up any minute. I might put it back on a bike one day. It is pretty loud, but it wasn't before I changed out the controller.

Michigan Mike · #7 (**permalink**) 11-27-2009, 07:50 PM

Does anybody know if brushless motors are louder or quieter than brushed motors?

jdcburg · #8 (**permalink**) 11-28-2009, 06:21 AM

They say brushless are almost silent. I have a brushed Unite 1016Z3 with a gear reduction unit on it. It has a gear whine under power. It sounds like an electric drill. However if it's on but not supplying power to the wheel (like going downhill), I can barely hear the motor over the wind noise - jd

TheE · #9 (**permalink**) 11-28-2009, 04:53 PM

A high pitched whine can actually be caused by the PWM of the controller. The current turning on-and-off causes the windings inside the motor to expand and contract at the frequency of the PWM signal, creating waves in the air and thus sound. Some controllers might bump the PWM frequency up past 20kHz so the sound is impossible to hear.

I guess you'd have to check the output of the controller with a frequency counter to know for sure. It very well could just be the gears.

Michigan Mike · #10 (**permalink**) 11-28-2009, 05:35 PM

When it gets more complicated than an on/off switch my head begins to give off a high pitched whine.

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