From my own observations, 0-2m/s noise is normal for the MS4525, 3m/s is worrying but still flyable. That said, some things you may want to try that helps reduce the noise:
- Make sure the sensor is stably mounted; the sensor is very sensitive to external disturbances. If it is allowed to vibrate together with the moving air, the noise will naturally be higher
- Set ARSPD_TUBE_ORDER to 0 to prevent false positive readings in the event that the static port is receiving excessive pressure.
I did some work on measuring airspeed sensor noise previously, which you can find here: MS5525 vs MS4525 airspeed sensor noise