Volume of ring changes
After the first ring of an incoming call the volume gets softer than the first ring
iPhone 14, iOS 16
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It is designed to reduce the volume as soon as the phone senses that you have heard it and are responding (not necessarily the first ring).
If Settings > Face ID & Passcode > Attention Aware Features is on, the ring volume will automatically decrease as soon as the phone recognizes that it has your attention. Also see: Turn Attention Aware features on or off on your iPhone or iPad Pro - Apple Support