Greetings ditalouisa,
It sounds like you have an issue with your audio levels on your iPhone. We know how important having a working iPhone is for you, and you’re in the right place to find a resolution.
Based off of the description you provided, you're likely referring to the headphone notifications that alert you when you've been listening to loud headphone audio for long enough to effect your hearing. To prevent this from happening on your device you will need to turn off Headphone Notifications. This setting also controls whether your iPhone volume will be automatically turned down as well. You can view steps on how to turn it off in Track headphone and environmental sound-level exposure in Health on iPhone, specifically this section:
If you listen to headphone audio for long enough at a volume that could affect your hearing, you can get a notification and have the volume automatically turned down to protect your hearing (iOS 14.2 or later).
- To get notifications for loud headphone audio, go to Settings > Sounds & Haptics > Headphone Safety, then turn on Headphone Notifications.
Note: Depending on your country or region, Headphone Notifications may be turned on by default, and in some countries or regions, you may not be able to turn off Headphone Notifications.
- To view the details for a notification, tap Browse at the bottom right of the Health screen, tap Hearing, tap Headphone Notifications, then tap the notification."
If you also use an Apple Watch with your iPhone, you may also want to check out the "View Noise Notifications for loud environmental sounds" section of that same support article. Additionally, you can find some great steps to help customize your headphone audio here: Customize headphone audio levels on your iPhone or iPad.
Cheers!
