If a Sonos alarm should play in just one room, test the selected room and grouping behavior during the day before relying on it overnight.
Set up a controlled test
Create a temporary alarm a few minutes ahead at a considerate volume. Select the intended room and review the grouped-rooms option in the Sonos documentation and app. Keep the current room grouping noted so you can compare the same alarm under a second configuration.
Read the result
Listen in both the intended room and another grouped room. Change only the grouped-rooms choice for the second trial. Record where sound actually played. Keep a separate reliable alarm while testing and remove the temporary alarm afterward. Sonos says the group at alarm time determines which grouped rooms play, not the group that existed when you saved the alarm.
Worked example
If a kitchen alarm wakes someone in an adjacent room through a grouped speaker, the solution may be the alarm’s room scope rather than lowering the entire system volume.
Documentation and next step
See the manufacturer’s instructions for requirements and settings. For a related decision, see sonos surrounds ambient vs full music test.
