To play background noise on your iPhone while using other apps, follow these steps:

  1. Open the "Settings" app on your iPhone.

  2. Scroll down and tap on "Accessibility."

  3. Select "Audio/Visual" and then tap on "Background Sounds."

  4. Turn on "Background Sounds" and choose your preferred sound.

  5. Adjust the volume of the background sound as needed.

  6. Exit Settings and open any other app.