Home button is quacking on iPhone 8+
What to do when a loud crackling vibration sound suddenly appears on my iPhone 8+? Oct 2019
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You might need to take it to get repaired if its making an audible "crackling" sound.
The vibration is normal and is caused by the haptics engine under the Touch ID button. You can lower the vibration amount by going into "Settings" under "General" and selecting "Home Button".
If you are still hearing the "crackling" noises, go get a second opinion in person from an Apple representative. They should be able to tell you whether the iPhone is functioning normally or is in need of repair.