Always check your levels. Background sound should be felt, not heard. If a viewer stops to think, "Wow, that's a loud refrigerator hum," you've probably pushed it 3dB too far.
Professional sound design is rarely just one track. To create a convincing "City" background, you might layer: Constant low-level traffic rumble. The Mid-Ground: Occasional car horns or sirens.
An incredible archive of thousands of historical and modern environmental sounds. Television Background-Sound Effect
If your characters are in a busy cafe but the background talk is indistinct, it creates a sense of isolation or focus on their private conversation.
You don't need a Hollywood budget to get high-quality television-style backgrounds. Check out these resources: Always check your levels
A specific pedestrian’s footsteps or a dog barking nearby. 4. Where to Find Them
The Invisible Character: How to Use Television Background Sound Effects Professional sound design is rarely just one track
A living room needs a subtle "room tone"—that low-frequency hum of a house. An outdoor scene needs "air," which might include wind rustling leaves or distant birds.