To change the alarm sound on your iPhone, follow these steps:

1. Open the Clock app on your iPhone.
2. Tap the Alarm tab at the bottom of the screen.
3. Tap Edit in the top-left corner.
4. Select the alarm you want to change.
5. Tap the Sound option.
6. Choose a new sound from the list of built-in alarm tones. You can tap each sound to preview it.
7. If you want to use a song from your music library as the alarm sound, tap Pick a song and select a song you have downloaded.
8. After selecting the sound or song, tap Back to return to the alarm settings.
9. Tap Save to confirm your changes.

You can also download new alarm tones from the Tone Store via the Sound settings if you want more options beyond the built-in sounds

. Additionally, you can customize the vibration pattern for the alarm in the same Sound settings if desired

. This method works on iPhone models including iPhone 14, 15, 16, and most iOS versions