What is the effect of MOSFET switching frequency on PMSM FOC drive?
The PMSM doesn't use hall sensors, it needs an encoder or some known sensorless techniques. Later it needs a start up procedure to determine the rotor position by injecting current signals and measuring voltage.
However if you made your own FOC, you should know what is the cause of this initial sound, also it is not clear why hall sensors are present in PMSM and what function they have in your FOC.