Idle servo produces noise when powered

[Sasha Zee]

I installed and powered servos, but they produce some cracking noise which can be barely heard, like motor tries spinning or something like that. However, motor idles and when it moves, the noise is much lowder, but similar.

Does anybody know what this could be or mean and whether it is normal or not?

Servos are digital, 7.2/6.6V powered from 6.6V source

 

[hamz9561]

It's not unusual to hear a bit of a hum on a digital servo with a small load on it such as a throttle return spring.

 

[Certified Mike]

I would just keep an eye on any increase in power consuption, like if you're killing the battery packs quickly. Also, be sure the servo isn't getting overly hot.

 

[EvhCo]

Same happens to me. I've noticed a drop of 0.07 volts on my integrated voltmeter when the humming is on, but that rarely is a problem.