Please note this is a digital servo. Digital servos perform quite differently to standard servos which have analogue motor drive amplifiers.

Digital servos are driven by a digital amplifier which has a small microprocessor to generate the necessary drive current to the motor.
This drive current is switched at very high speed, hence this will be audible as a high frequency buzzing - this is not a fault at all, this is how they work. The audible noise is a result of the servos very tight centring ability, it will constantly hunt around the exact centre point minutely to enable best possible resolution.

All digital servos sound different from standard types and they tend to exhibit this type of high frequency switching noise. If you are unsure this is suitable for your needs buy an analogue servo.

Ultra High Speed Digital Servo

The E-Power 20g micro servo features nylon gears inside. Providing you the lighter weight than metal gear servos. The response time of this servo is 0.06 sec at 4.8V or 0.05 sec at 6V which is amazingly fast.

Specifications:

Size 35.0mm x 15mm x 34mm (1.4" x 0.6" x 0.94")
Speed 0.6 sec/60� (4.8V) or 0.5 sec/60� (6V)
Torque 3kg @ 4.8v
Weight 20 grams

Please Note: 6 volts really does mean 6 volts not 7+ as is likely with 5 fully charged 2nd generation NMH cells