Samsung
Change Timer Volume auf Samsung
Samsung splits alarm-related sounds into separate channels. Ringtone, media, and notification volume each have their own slider in the system settings, but the timer alarm is controlled only inside the Clock app itself.
This is why pressing the physical volume buttons while a timer is running, or adjusting the general sound settings beforehand, has no effect on how loud the timer rings. The volume for the timer sits in a dedicated menu that is easy to miss because it looks like a normal settings screen.
Where the timer volume actually lives
Open the Clock app, then follow this path: Tap on Clock ➔ Open the Menu ➔ Tap on Settings ➔ Tap on Sound ➔ Swipe left or right to adjust the timer volume. Swiping the slider all the way to one side mutes the timer completely without disabling the timer function.
If your goal is to silence alarms or notifications system-wide, this is the wrong fix; that requires the general sound settings instead. Use this menu specifically when the timer itself is too quiet, too loud, or needs to be muted while other sounds stay untouched.
One side effect: since this volume is stored per Clock app profile, resetting the app or reinstalling it can return the timer volume to its default level.