The small partner of the iPhone 13 series model, I don't know if I have found that the "Phone Noise Reduction" button is missing in the "Settings - Accessibility - Audio/Visual" option.
If the phone noise reduction function is turned on, it can reduce the environmental operation during the call, which is available in previous models, even the old iPhone 6S device can find "phone noise reduction" in "audio/vision", but the four iPhone 13 released this year do not have this option.
Some netizens have reported that the iPhone 13 series has not had a "phone noise reduction" switch button For two months.
In the iPhone manual on Apple's official website, it can also be seen that the iOS 15 system can adjust the audio settings through the mono audio, balance, and telephone noise reduction in the "Audio/Visual" setting project. Usually, if some models don't support a setting, Apple adds a description. It can be seen that the iPhone of the iOS 15 system should all support the enabling of "phone noise reduction".
If it is not a hardware problem, it is most likely a bug in iOS 15. According to the feedback of netizens, Apple support said that Apple engineers are studying the problem, but there is no clear timetable at present, and it is hoped that Apple can completely solve this problem through follow-up software updates in the future.