In a previous post I talked about Visual Poetry as being "poetry for the eyes". Fluxus, being Intermedia, is all about the spaces in which different media intersect, so audio art, sound art, and noise recording, can be described as "art for the ears". In the late 20th century many artists trained in traditional visual theory and technique began to expand their artistic practice into the aural sphere. The most common audible art is familiar to most people in the form of the "sound track" to a video. When artists began producing motion picture art, whether in "high-tech" films, or using "low-tech" video cameras, sound was often incorporated to accompany the visual elements. This work is commonly referred to as being "multimedia". But at around the same time as some artists were producing art videos without sound, other artists began producing art audios without video imagery. This audio art has become in effect a new type of "visual" art, although it is invisible to the eyes.
Examples of my own audio art are on my website at; https://www.digitalsalon.com/revich-fluxus.html. There are many other examples of work on the Fluxus Podcast, maintained by Walter Cianciusi.