Apple's mobile phone has sound and can't find the source.

If the shutdown of Apple's mobile phone is not a special case, the specific file location can't be found.

If it's the voice bell that comes with the system, it can't be found. If it is a ringtone downloaded later, you can find it by connecting to iTunes software.

Some ringtones are probably cached files, such as those downloaded by WeChat browsing, or some audio files in web pages.