Two tones within a critical band interact to reduce total loudness

Evidence

Two tones of equal level with a frequency separation greater than the critical bandwidth produce a loudness which is larger than the loudness of a single tone with a frequency midway between that of the two tones, and with a level corresponding to the total intensity of the two tones. With increasing frequency separation of the two tones, loudness increases. This means that loudness is not produced from separate spectral components, but rather the two components influence each other, especially if their frequency separation is small. Only for quite large frequency separation, where the two single tones do not influence each other, does a loudness value occur which corresponds to the addition of the loudnesses of each tone. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1247

Categorization

• XREF: Connects to the reader’s existing knowledge of the critical band concept introduced earlier in this book.