Wide bandwidth noise sounds as loud as a narrower tone despite lower level

Evidence

To illustrate the process of the loudness model, two example stimuli are shown as they are passed through the different steps of the model in Figure 4–8. Each of these example stimuli has a similar loudness, in order to show how the loudness model might predict the loudness of two sounds that are very different in overall level and bandwidth. The first sound is a 57 dB SPL, 1000-Hz tone, and the second is a band-limited noise with a total power of about 43 dB SPL. These two sounds are similar in their loudness and loudness levels, which are 3.4 sones and 56.8 phons, respectively, as determined by the loudness model. … The top panel of Figure 4–8 illustrates the acoustic representation of these sounds in the form of the spectrum. The middle panel shows the excitation patterns of these two sounds, which is a model of the internal representation of these two stimuli. Finally, the bottom panel illustrates the specific loudness pattern. The pure tone has a higher dB SPL level, excitation, and maximum specific loudness than the noise. However, the noise has a wider bandwidth and is therefore subject to spectral loudness summation. The area under the two specific loudness pattern curves is the same for the tone and the noise, which is why the two stimuli have the same loudness. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 780

Categorization

• XREF: Connects to earlier chapters’ coverage of auditory filters and excitation patterns, and prefigures what hearing loss does to loudness summation.