Open the Clock app and go to the "Alarms" tab, then select the alarm you want to edit. Tap the "Sound" option and scroll down to choose a new preinstalled sound or tap "Pick a Song" to choose a song ...

Select an option from Settings > Sounds & Haptics > Ringtone to set a new default ringtone. You can use a third-party app to create a custom ringtone. Select it as the default in the Ringtone settings ...

Have you ever missed a call on your iPhone because the ringer volume is low? One of the most frustrating experiences is missing an important call because your iPhone’s ringer volume is too low.