A continuous beep usually indicates a problem that requires attention, such as a degraded or crashed volume, an abnormal SSD cache, or a malfunctioning cooling fan. Check DSM first:
1. Sign in to DSM and open Notifications in the upper-right corner to see the reported cause.
2. Go to Control Panel > Hardware & Power > General > Beep Control and check Reason for current beep. [1]
3. If the volume is degraded or crashed, follow DSM’s repair/recovery instructions before muting the alert. A blinking orange STATUS indicator may also mean that the volume is degraded, crashed, or missing. [2]
4. If the SSD cache is abnormal, follow the corresponding DSM instructions.
5. If the fan is malfunctioning, clean dust from the NAS and ensure it is operating in a suitable-temperature environment. If the problem remains, the fan may need service. [1]
To stop the sound, go to Control Panel > Hardware & Power > General > Beep Control and click Mute in DSM 7.0 and later, or Beep Off in DSM 6.2 and earlier. [1]
Do not treat muting as a repair: first check Notifications, storage-pool/volume status, drive indicators, and the fan so the underlying fault is addressed.
Sources: [1] Synology Knowledge Center, “My Synology NAS keeps beeping. What can I do?” [2] Synology Community, “How to reset my DS212 from continuously beeping.”