How it works
A fan curve relates a chosen temperature measurement to a requested fan speed. The controller may live in motherboard firmware or supported device software. Which sensor drives the curve matters: a processor temperature can rise rapidly while case air changes more slowly. A case fan and a cooler fan therefore need not use identical settings. PWM and voltage-controlled fans also require appropriate control modes.
The aim is reliable cooling with acceptable noise, not the lowest possible fan speed. A curve that reacts to every brief temperature spike can make the fan continually accelerate and slow down. Supported response delays or hysteresis can reduce that behaviour, but must still allow cooling during sustained work. A fan may fail to start reliably below its practical minimum; a displayed percentage is not a universal rotation speed.
Practical checks
Keep a record of the original profile and use the manufacturer's supported controls. Confirm the correct sensor, fan header and control mode before adjusting anything. Change a limited setting, monitor temperature and rotation during the workload you actually use, then test a longer sustained load. Restore the known working profile if temperatures or behaviour become unsuitable. Do not silence a fan warning without identifying whether it indicates a genuine cooling problem.