Loudness rises with bandwidth beyond the critical band despite falling pattern height

Evidence

In Fig. 8.7, the continuous rise of loudness is plotted as a function of bandwidth for constant sound pressure level. This increment of loudness as a function of bandwidth can be described as a spectral effect. For the same overall intensity and centre frequency, any stimulus narrower than a critical band, even a pure tone, produces a pattern of specific loudness corresponding to that shown for the noise one critical band in width. The SPL falling into one critical band is responsible for the specific loudness produced. Therefore, bands narrower than a critical band are represented by a pattern of specific loudness that is independent of bandwidth. However, the loudness pattern begins to change as soon as the width of the noise exceeds the width of the critical band. For a fixed overall level, the height of the pattern decreases but at the same time it extends over a greater portion of the critical-band rate scale. The extension along the critical-band rate produces an increment of the area that is larger than the decrement produced by the reduction of height. This way, the total loudness increases with increasing bandwidth even though the height of the pattern decreases. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1288

Categorization

• DEFINE: Explains the spectral effect, the mechanism by which loudness integrates acoustic energy across critical bands.