Go to Notifications in DSM and check for possible causes, then go to Control Panel > Hardware & Power > General > Beep Control and look at Reason for current beep to determine why it is beeping. The knowledge base mentions these possible causes:
- Volume has degraded → refer to the storage pool repair article in DSM help.
- Volume has crashed → refer to the volume crash article.
- SSD cache is abnormal → refer to the SSD cache FAQ.
- Cooling fan is malfunctioning → dust the Synology NAS first and make sure it is in an environment with appropriate temperature; if the issue persists, the fan may be broken.
- If the beep is due to a malfunction on some models, you can use the Beep Off / Alarm silence button to deactivate the beep sound.
From the hardware manuals, the Beep Of Button / Alarm silence button is specifically for deactivating the beep that sounds when a malfunction occurs.
Relevant notes:
- If the fan malfunctions, the NAS may emit a beeping sound.
- On some older models, the manual says the Beep Off Button deactivates the beep when a malfunction occurs.
- This can silence the alarm, but it does not fix the underlying cause, so you still need to check the reason in DSM and resolve it.
Sources used: [9], [11], [12], [13], [14], [15]