why are servos so unnecessarily loud?
Rhetorical question?
Weedpharma
bmarconi:
why are servos so unnecessarily loud?
Because they are meant to be used in radio control devices, which are typically so far away from anyone listening (not to mention the noise generated by the vehicle's propulsion system and other noises) - that the extra audible noise from the gear train of the servo doesn't matter.
Furthermore - servos are manufactured to be inexpensive. This means a certain amount of slop in the gear train, which adds to the noise. Also, regular spur gears are used - instead of more expensive (often much more expensive) solutions to lower noise from the gear train (such as helical cut gears, double herringbone gears, etc).
If you want less noise, you'll have to pay for it. I suspect (but I don't know) that some of the so-called "smart servos" - such as those from Robotis and others - might have less noise, since they are designed for robotics and animatronics, and not R/C purposes. But you will have to pay the price if you want that level of precision and noise reduction.
They use dry spur gears, which are loud. If your car gear box used spur gears rather than
helical it would scream. Actually you can hear this as reverse gear is normally spur.
Helical gears are much smoother but have the problem of exerting axial force meaning
thrust bearings of some sort are needed.
Really quiet gears are usually helical, lubricated and in a solid sound-proof casing. (and
a lot more expensive to make)