Keeping total level constant while widening bandwidth requires lowering spectral density

Evidence

The intensity density, dI/ df, also called spectral density, is frequency independent for white noise which is normally created by a noise generator. Adding a band-pass filter in sequence with the noise generator, and varying the bandwidth of the filter, leads to sounds with unchanged intensity density. Their total intensity, however, changes in direct proportion to bandwidth. Because we already know that loudness depends strongly on sound level, we have to take care to keep the sound pressure level of the noise constant when the bandwidth is changed. This means that the total sound intensity, given by the area below the curves in Fig. 8.6, has to be kept constant. This is only possible by reducing the intensity density in the same way as the bandwidth is increased, as demonstrated in Fig. 8.6 at a centre frequency of 1 kHz. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1197

Categorization

Category: Causal Relationships

Related

• Loudness rises with bandwidth beyond the critical band despite falling pattern height (similarity 0.88)
• Noise loudness is level-independent until bandwidth exceeds the critical bandwidth. (similarity 0.86)
• Widening a sound’s bandwidth beyond one critical band raises perceived loudness at unchanged intensity. (similarity 0.84)
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• Wider bandwidth increases perceived loudness at equal sound pressure (similarity 0.83)
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• Sharpness depends primarily on spectral content, not on level or bandwidth. (similarity 0.83)
• Wide bandwidth noise sounds as loud as a narrower tone despite lower level (similarity 0.83)
• Loudness increases when sound energy spreads across critical bands to fire extra nerves (similarity 0.83)
• Loudness grows with bandwidth via area tradeoff except at extreme levels (similarity 0.83)