Hello Glockers,
Welcome to Apple Support Communities!
We want to help you adjust the timer volume.
You can have Siri adjust the volume, or by using the volume buttons, or in Settings.
See here:
"Adjust the volume on iPad
Use the volume buttons on iPad to adjust the volume of songs and other media, alerts, and sound effects. (The volume buttons are either on the side or the top of your device, depending on your model.)
You can also use Siri to turn the volume up or down.
Siri: Say something like: “Turn up the volume” or “Turn down the volume.” Learn how to use Siri.
You can use Control Center to silence audio alerts and notifications."
This Apple Support page has the full details: Adjust the volume on iPad - Apple Support
We hope this helps to adjust the volume as you want.
Please let us know if you have further questions.
Cheers!