If your vehicle is showing whining noise that gets louder as engine rpm increases, here are the most likely causes and the parts you'll need to fix each one.
A low fluid level introduces air into the power steering system, causing the pump to whine loudly as engine RPM increases. If the fluid is full, the internal pump mechanism itself may be failing.
The bearings inside the accessory drive pulleys dry out and wear over time. As they spin faster with the engine, they emit a high-pitched whine or squeal.
Worn internal bearings or a failing diode trio in the alternator will create an electrical or mechanical whining sound that directly matches engine speed.
If the transmission fluid is low, the transmission fluid pump will suck in air and whine loudly as engine RPM increases. This frequently occurs after an improper fluid service where the transmission was underfilled.
The water pump bearings can fail and whine as they rotate with the engine belt. This often precedes a coolant leak or engine overheating.
A poor electrical ground allows the alternator's electrical frequency to be heard as a whine through the car speakers. This is highly common after installing an aftermarket stereo or amplifier.