1. Camera Image Stabilizer (OIS):
Many smartphones with optical image stabilization have lenses that are mounted on small movable parts.
When the phone is turned off or the camera app isn’t active, these lenses aren’t locked in place — so they can make a slight rattling sound when you shake the device.
Typical sound: a faint, metallic clicking or rattling noise, especially near the camera area.
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2. Autofocus Module:
The autofocus mechanism can also move slightly when it’s not powered.
The sound is similar to the OIS noise but usually a bit quieter.
