The loudness of the motor mainly comes from the fact that current through coil is turned on and off in frequencies bellow 30 kiloHertz. The sound mainly goes away when microstepping as this frequency increases over audible range.
The 12v or 5.2v or 2.8v that is written on the motor has nothing to do with what voltage you run it through. You actually need to run the motor at several times more that voltage, e.g. most ppls on cnczone will advice x10 times that value. The ratings on the motor have more to do with ohms law and overall power-watts rating of the motor than it has to do with actual application you want it in.
For example since reprap uses 12V psu, there is no chance you can put 1amp of current through a coil with 40 ohms resistance, because simply ohms law says it would take max 0.3A. In practice that shouldnt be peaked value as the driver needs to switch much more before that happens, so its fast enough, because the 0.3A peak takes a lot of time to hit as the waveform is curving down - almost flat. Also generally speaking high coil resistance means thin wire and more windings, so generally higher inductance, thats at least one of the reasons ppls warn against higher inductance with voltages like 12v. Perhaps another is that high inductance has a harder time increase or collapse its field in a current reversal bipolar motor, so perhaps this ppls dont say just "coil resistance" but more generally "higher inductance" which somehow includes both.
To run a motor 5.2v / 5.8A that means a max 0.9 ohms (ohms law) but again thats practically much less coil resistance, probably again an ideal peak would be much xxlog times lower than that, and thats kinda impossible.
To actually check out ratings of a motor, they usually give 2 of three by ohms law and you can figure out whats missing: e.g. they give either current and coil resistance, or voltage and current, etc. This voltage should be much lower, several times lower than what you plan to actually use. This is about the same thing to say that the ohm's law max current is many times much higher than the peak point where stepper driver will turn off or reverse the coils.
The 12v or 5.2v or 2.8v that is written on the motor has nothing to do with what voltage you run it through. You actually need to run the motor at several times more that voltage, e.g. most ppls on cnczone will advice x10 times that value. The ratings on the motor have more to do with ohms law and overall power-watts rating of the motor than it has to do with actual application you want it in.
For example since reprap uses 12V psu, there is no chance you can put 1amp of current through a coil with 40 ohms resistance, because simply ohms law says it would take max 0.3A. In practice that shouldnt be peaked value as the driver needs to switch much more before that happens, so its fast enough, because the 0.3A peak takes a lot of time to hit as the waveform is curving down - almost flat. Also generally speaking high coil resistance means thin wire and more windings, so generally higher inductance, thats at least one of the reasons ppls warn against higher inductance with voltages like 12v. Perhaps another is that high inductance has a harder time increase or collapse its field in a current reversal bipolar motor, so perhaps this ppls dont say just "coil resistance" but more generally "higher inductance" which somehow includes both.
To run a motor 5.2v / 5.8A that means a max 0.9 ohms (ohms law) but again thats practically much less coil resistance, probably again an ideal peak would be much xxlog times lower than that, and thats kinda impossible.
To actually check out ratings of a motor, they usually give 2 of three by ohms law and you can figure out whats missing: e.g. they give either current and coil resistance, or voltage and current, etc. This voltage should be much lower, several times lower than what you plan to actually use. This is about the same thing to say that the ohm's law max current is many times much higher than the peak point where stepper driver will turn off or reverse the coils.