PWM

[PilatusPC-6]

Hi everyone, hope all is well, I would like to make a question regarding PWM setting in the ESC. The setup that I'm using is an Aerostar 80 Amp ESC and a Turnigy G-46 ( .46 glow ) brushless outrunner motor, these are powered by a 4s lipo. In the PWM setting of the ESC I got 8 Kz 16 Kz and 24 Kz, as I can't get to know how many poles does this motor have I tried running the motor on all the three settings to notice if there will be any noticable difference, what I just noticed is that when I ran the motor on16Kz at a certain revs I heard a screeching noise come out of the motor, leaving the same setting for the timing I changed the PWM setting to 24 Kz and the noise went away at the same revs as when ran on 16 Kz. Does anyone know what's the best PWM setting for the said motor, any info or help would be greatly appreciated. BTW I did the maiden/test flight with the above setting and haven't noticed any of the components (both ESC and motor) that had any excessive heat after a 5 min flight.