What is meant by 'fade out' in sound control?

The term 'fade out' refers specifically to the gradual decrease in the volume of sound until it is no longer audible. This technique is commonly used in various forms of media, including theatre, film, and music, to create a smooth transition away from a particular sound or piece of audio. By bringing the volume down rather than cutting it abruptly, a fade out can provide a more polished and seamless listening experience, allowing the audience to better absorb the context or emotions of the moment.

In contrast, the other options do not accurately reflect the definition of 'fade out.' Increasing sound intensity implies a rise in volume rather than a decrease. Adding background music involves introducing an additional layer of sound rather than diminishing an existing one. Stopping sound effects immediately would not align with the gradual nature of a fade out. Thus, the correct understanding of 'fade out' emphasizes the process of bringing the volume down deliberately and carefully.