Acoustic encoding is the process of converting information into a sound-based code that the memory system can store. When you repeat a phone number under your breath or hear a melody that sticks in your head, you are relying on it.

In the classic multi-store model of memory, acoustic coding is especially important in short-term or working memory. Letters that sound alike—B, C, D, T—are more easily confused in immediate recall than letters that look alike but sound different. The phonological loop component of working memory is thought to be the specialized system that maintains acoustic information through rehearsal.

Long-term memory also uses acoustic features. Songs and poems learned years earlier can be retrieved with surprising accuracy, partly because the sound pattern itself provides a rich retrieval cue. People with certain forms of amnesia may retain the ability to learn new melodies even when they cannot form new episodic memories.

Acoustic encoding is not the only route into memory—visual and semantic codes are equally important—but it is the one that turns the fleeting sound of language into something that can be held and examined.