If you don't have an Apple Watch, Phone-Only mode delivers alerts as extended silent vibrations straight to your phone — designed to wake you without sound.
Settings › Alert Delivery
• Phone-only alerts are silent — they vibrate, they don't play a sound, so they won't wake your partner.
• They're built to keep buzzing to wake you even when the phone is locked and the screen is off.
• Have a supported Apple Watch? Leave this off — the watch on your wrist is the most reliable way to wake just you. See the watch guides.