Relationship between Motor Speed & Noise

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Relationship between Motor Speed & Noise

Postby om_tech_support_JT » Wed Jun 06, 2012 1:49 pm

Q: I'm looking at your BLH series brushless motor systems for a museum display application. Since it will be inside a museum, I need to make sure I keep the noise down to a minimum. I don't have a specific decibel rating I"m looking for, but it needs to be quiet enough so it doesn't bother/annoy the visitors when they're walking by. I've heard that motor speed makes a difference in noise. I'm basically trying to pick a gear ratio for the BLH 30W motor, but I'm not sure if I should choose a motor that runs at a high speed with a high gear ratio, or a motor that runs at a lower speed with a low gear ratio. Can you help explain this?

A: There are two components of noise: electrical noise and audible noise. In a brushless motor system, electrical noise is mostly generated by the driver, and audible noise is typically generated by the motor. At low speeds, the frequency of the electrical noise generated by the driver is actually low enough that it's audible to the human ear. At high speeds/frequencies, the human ear cannot detect this noise. For the motor, more noise is generated by the ball bearings and the gears in the gearhead as speed increases. In most cases, motor noise is greater than electrical noise.

For this reason, we would suggest that you use a low gear ratio and a lower motor speed to achieve more noise reduction.

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