ELi5 Why do some electric motors make noise and others don’t

Question

For example, electric cars are quiet, electric drills/lawn mowers are noisy

In: 3

Answer 1

In general, the smaller the motor, the higher the ram. This is not always the case, but it’s not a bad rule of thumb.
Power tools used what is called a series motor, although that is changing now, and electric mowers used them too. Series motors are characterized by having extraordinarily high speeds but not very high torque. This is remedied by gearing the output down. That’s what makes those small motors so noisy, the combination of the high speed armature and the gears. There’s also air movement (vacuum cleaner), vibration (imbalance) and bearing noise.