Alarm volume too low, or dropping on its own?
A slow, quiet failure: the alarm still goes off, you just stop hearing it. This one has a small number of real causes, and unlike a missed alarm you can reproduce it on demand.
Android has more than one volume
Ring, media, alarm, notification and call each have their own level. Pressing the volume keys on the home screen usually moves ring or media — not alarm. So a phone can be "at full volume" with the alarm stream near the bottom. Open Settings → Sound & vibration and look at the alarm slider specifically.
What lowers the alarm stream without you noticing
- Routines and modes. Bedtime mode, Focus, driving mode and automation apps can set volumes on a schedule. If your alarm got quiet around the time you enabled a night routine, start here.
- Headphones and Bluetooth. Some phones remember a separate level per output. Plug in headphones, change the volume, unplug — and the value you set can follow you back.
- Adaptive or auto volume features. Several manufacturers ship a feature that lowers volume in a quiet room. A bedroom at 3am is the quietest room your phone will ever measure.
- The alarm app itself. Many alarm apps simply hand playback to the system alarm stream, so whatever moved that stream moves your alarm too.
Fade in is not the same as quiet
A gradually rising alarm is a good feature — it wakes you without the jolt. It becomes a problem when the ramp is long and you sleep through the quiet part. If your app offers it, check how long the ramp is and whether it reaches full volume at all.
Headphones that fall out
If you fall asleep with earbuds in and they come out overnight, an alarm routed only to the headphone output plays into an empty pillow. Look for an option that forces the alarm through the speaker regardless.
The fix that actually holds
The durable answer is an alarm app that stores its own volume per alarm and applies it to its own player, instead of inheriting whatever the system alarm stream happens to be at. Then a routine, a car mode or a music app cannot quietly turn your morning down.
Wakebell
Wakebell keeps a volume per alarm, separate from media volume. Fade in is optional and reaches full in 30 seconds, not several minutes. It plays through the speaker even with headphones connected, so an earbud that falls out overnight does not cost you the morning. And an alarm history records what actually happened each time.