Underhear
Underhear refers to the practice of listening to audio content, typically music or spoken word, at a volume so low that it is barely perceptible or is primarily a background ambiance rather than a primary focus. This can be done intentionally for various reasons, such as creating a calming atmosphere, aiding concentration without distraction, or enjoying the subtle presence of sound. The term suggests that the audio is almost subliminal, heard "under" other activities or conscious thought.
This approach contrasts with active listening, where the listener is fully engaged with the audio content.