You can use your iPhone to continuously listen for certain sounds—such as running water, a doorbell, siren, crying baby—and notify you when it recognizes these sounds.
Note: Don’t rely on your iPhone to recognize sounds in circumstances where you may be harmed or injured, in high-risk or emergency situations, or for navigation.
Go to Settings > Accessibility > Sound Recognition, then turn on Sound Recognition.
Tap Sounds, then turn on the sounds you want iPhone to recognize.
Tip: To quickly turn Sound Recognition on or off, use Control Center.