I have reported this issue more than 20 times via feedback app since 2020 when iPhone 12 came out.
I don’t want to call them on purpose, because they always do the same thing.
They want to check your device , they want you to perform all sort of tests, analysis, restarts and reset keeping you on the phone for hours.
For this specific issue I have tested iPhones on every chance I could.
6s, 7, 8, 10, 11, 12 13 in malls, Apple store in front of them, from friends, just doing a simple test: in “sound&haptics, volume all the way up and assigned the same sound to ringtone and text tone.
I choose “Sonar” because is very loud.
Ringtone “Sonar” and Text Tone “Sonar”.
All those iPhones behaved in the same way: Alerts volume was and is too low, I miss a lot of notifications, all iPhones have this issue and it’s unacceptable for a 1000$ device. Period.
I presume almost all Apple engineers have an iPhone, for personal use or for work. How is it possible they didn’t notice this problem even on their own phone?
The issue has been reported several times by several customers, the engineers are aware of the issue and they should perform all those analysis on their own iPhones and fix it.