Since charging your iPhone is probably something that you do a lot, you might have noticed that when you plug in your iPhone to charge, it emits buzzes or chimes.
You can tell a lot about your iPhone if you pay attention to these buzzes or chimes.
When you plug your iPhone into charge, you’ll hear a chime or feel a buzz (depending on whether it is in silent mode or not). This is the “I’m charging” announcement.
If shortly (three seconds to be precise) after this first buzz or chime, you get a second buzz or chime, this means that the iPhone is fast charging. For this to work, you’ll need a compatible iPhone (officially an iPhone 8 or higher), USB-C-to-Lightning cable, and a USB-C charger capable of outputting a minimum of 15W, and for the battery to be discharged to below 50%.
If you hear three buzzes or chimes, then this is a sign that USB Restricted Mode is enabled. This is a privacy feature that prevents USB accessories that plug into the Lightning port from making data connections with an iPhone, iPad, or iPod Touch if your iOS device has been locked for over an hour. You shouldn’t hear this when connecting your iPhone to a charger, and shouldn’t affect charging at all no matter what device you plug your iPhone into, only data transfer.
If you want to stop your iPhone buzzing when in silent mode, head over to Settings > Sounds & Haptics, scroll down to System Haptics and toggle this to off.