NC curves originated to rate speech intelligibility, not listener satisfaction

Evidence

In North America, the NC curves are widely applied to define acceptable background noise levels for audio environments. “[the NC curves] are intended to be octave band noise levels that just permit satisfactory speech communication without being annoying”; so said the creator of these curves, Beranek, as reported in Tocci (2000). — Toole, Floyd E, Sound reproduction- the acoustics and…, 936

Categorization

• DEFINE: Clarifies what NC (Noise Criterion) curves actually measure and their original design purpose.