The acoustical conditions in a classroom may severely impair listening, which in turn impairs learning. To safe-guard against inferior listening conditions government agencies and professional societies have established building codes and recommendations for acceptable signal-to-noise ratios (SNR) and reverberation times (RT) in classrooms. Codes and recommendations are based on conditions required for speech intelligibility and correct identification of spoken words and isolated sentences.

Correct identification of what was said is a necessary condition for memory and learning, but it is not a sufficient one. There is a gap between speech intelligibility and memory and the size of that gap is a function of the intelligibility of the spoken message and how much the message taxes the individual's limited working memory capacity.

I will discuss how SN, RT and their combinations change speech intelligibility and memory of spoken messages. Although the characteristics of the spoken material and the individual's working memory capacities can be assessed independently of each other, there is a functional equivalence between them. A difficult task and a lack of skill are two sides of the same coin.

In a better world building codes and recommendations for classroom acoustics should be based on memory and learning rather than on speech intelligibility alone.