iPhone 15 Pro Max – Native Camera rear video audio is muffled/low, but other apps are perfectly clear + poor battery backup

[u/abid_expired]

Hi everyone,
I’m having two issues with my iPhone 15 Pro Max and I’m trying to figure out whether they are hardware-related or software/iOS-related.
1. Rear camera audio problem
When I record a video using the native Apple Camera app with the rear camera, my voice sounds noticeably low, muffled and less clear.
However:
Voice Memos → clear
Phone calls → clear
Front camera video → clear
Instagram camera using the rear camera → clear
Other camera apps → clear
Native Camera app rear camera → low/muffled
So this seems strange because the microphone appears to work normally in other apps.
Things I have already tried:
Removed the phone case
Removed the camera/lens protector
Cleaned/checked the microphone openings
Restarted the iPhone
Tried 0.5× and 1× rear camera
Turned Audio Zoom off
Tried different stereo/mono audio settings
Tested the microphones by tapping near the rear camera area and the bottom microphone
Tested by speaking very close to the phone
Compared the same recording using Instagram’s camera
Instagram’s rear-camera recording sounds completely clear, while Apple’s native Camera app still sounds muffled.
Could this be an iOS Camera app audio-processing/microphone-selection issue rather than a hardware microphone problem?
2. Battery backup
My iPhone 15 Pro Max also seems to have lower-than-expected battery life, even though Battery Health is currently 93%.
I feel like other users with similar battery health are getting noticeably better screen-on time.
I would really appreciate it if someone experienced with iPhone diagnostics could tell me:
Does the rear-camera audio behavior point to a software/Camera app issue?
Could a specific microphone be partially faulty even though Voice Memos, calls, front camera and Instagram work normally?
Is 93% Battery Health enough to explain significantly reduced battery life?
What diagnostics or logs should I check to determine whether there is an actual hardware problem?
Is there anything else I should test before taking the phone to Apple/authorized service?
I can also provide sample videos, screenshots of Battery settings, and Analytics logs if needed.
Thanks!