Greetings RogerAppleiTune,
Thanks for visiting the Apple Support Communities! I understand the ringtone becomes unexpectedly quiet after the first ring on your iPhone.
When Attention Aware features is enabled on your iPhone, the volume sound of the alerts will become quieter when looking at your device. You can see that information outlined in the following article: About Attention Aware features on your iPhone X or iPad Pro - Apple Support
Even if you don’t enroll in Face ID, the TrueDepth camera on iPhone X or later, or iPad Pro 11-inch or iPad Pro 12.9-inch intelligently activates to support attention aware features. For example,
- When you’re looking at your device, your display will not dim until you stop looking at your device.
- If you're looking at your device, it will lower the volume sound of your alerts.
If you don’t want to use these features, go to Settings > Face ID & Passcode and turn off Attention Aware Features"
Kind regards.