From the knowledge base, the only documented options for fan speed control are the DSM fan modes:
- Full-Speed Mode
- Cool Mode
- Quiet Mode
- Low-Power Mode — only on specific models
You can change them in Control Panel > Hardware & Power > General > Fan Speed Mode.
The knowledge base says these options vary by model and hardware configuration, and some modes may be disabled when additional network cards are installed.
If the problem is a malfunctioning fan or a fan warning, the available manuals describe only physical replacement of the fan/PSU fan, depending on the model. For example:
- Some models support replacing the fan by opening the unit or expansion unit and installing a new fan.
- For units with PSU fans, DSM controls the NAS fans, but PSU fans are controlled by the PSU.
For your specific model, the knowledge base does not provide a dedicated “fix noisy fan” procedure beyond:
1. Check whether your model supports fan speed modes in DSM.
2. If a fan is malfunctioning, replace the fan according to the model manual.
The knowledge base has no more specific answer for a universal fix beyond those points.
Sources used: [10], [11], [14], [1], [2], [3], [4]