For example, electric cars are quiet, electric drills/lawn mowers are noisy
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The noise often comes from what the electric motor is driving. In the case of the lawn mower, most of the noise is coming from the cutting blade spinning in the air. In the case of the drill, the gears in the drill make much of the noise. The gears in drills are usually what are called “straight cut gears”. The gears in a car’s drivetrain are almost always “helical cut gears”. Helical cut gears are quieter than straight cut gears. As Fred2718 mentioned, cooling fans for the motor can also contribute to noise.
Electric motors can also have “torque ripple”. That is, the torque output of the motor might not be perfectly constant as the motor turns through a revolution. This will cause a vibration which will contribute to noise. Electric car designers use motor designs that minimize or eliminate torque ripple.
As a final note, in a piece of equipment that is in good shape and properly lubricated, friction is generally responsible for very little noise. But, if you ever had a motor (like on a fan) that suddenly developed a squeal, that is a friction problem in a bearing that is out of lubrication.
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