Audio ducking is a feature on the iPhone that automatically reduces the volume of background audio, such as music or videos, when there is another audio signal, such as a phone call or VoiceOver speaking. This feature is turned on by default on iPhones, but it can be turned off by going to Settings > General > Accessibility > VoiceOver > Audio and toggling off the Audio Ducking option. Audio ducking is a useful feature that helps maintain clear and uninterrupted communication during calls and is especially useful in various situations, such as FaceTime calls, video conferencing, or listening to podcasts while answering calls.