1. It is possible that the earphones are broken. There is no solution. Can you try plugging in another front end to see if there is sound?

2. The battery may be out of the package, causing voltage instability. Are you sure? It is an original battery

3. It is possible that your sound source is not good, so there is noise when listening to music. Classical music recorded earlier will have a background noise

4. If you are If you use better quality headphones, it may be the background noise of monitoring. There is no solution to this, unless you are willing to add a sound card or something.

5. It may be the magnetic effect caused by the close circuits in the mobile phone. Affect the coil, you can take a look at the induced current in high school physics, this is it

Let’s talk about it for now, you can refer to it yourself

Anyway, my htc also has a noise floor, and the headphones If you listen more closely, the noise floor is very obvious. Even Sony's professional MP3 players have a noise floor, so it's normal to turn on the noise floor, as long as it doesn't affect listening to music.