iPhone 12 alert sounds are very soft

I just upgraded from an iPhone XS to an iPhone 12 Pro.

All the alert sounds are significantly quieter on the 12 Pro.

Obviously I have turned up the volume to full in Settings.

I'm talking about the shut-off click, the camera click, alarm sounds, notifications, etc etc

Music playback is still as loud as on the XS.

Is there a fault with my new phone?

Is it a software thing? (iOS 14.5)