Perceived loudness depends on frequency content and duration, not just sound pressure level

Evidence

Each attribute of an auditory event depends typically on many properties of the sound event. For example, the loudness of an event depends not only on the sound pressure level of the sound event, but also on, for example, the frequency content and the temporal duration of sound. Often, one of the physical properties of a sound event is dominant, like the fundamental frequency of a tone complex that mostly defines the pitch. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 858

The pressure amplitude of a sound wave does not directly relate to its perceived loudness. In fact, it is possible for a sound wave with a larger pressure amplitude to sound quieter than a sound wave with a lower pressure amplitude. How can this be so? The answer is that the sounds are at different frequencies, and the sensitivity of our hearing varies as the frequency varies. Figure 2.13 shows the equal loudness contours for the human ear. These contours, originally measured by Fletcher and Munson (1933) and by others since, represent the relationship between the measured sound pressure level and the perceived loudness of the sound. The curves show how loud a sound must be in terms of the measured sound pressure level to be perceived as being of the same loudness as a 1 kHz tone of a given level. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 623

As well as frequency and amplitude, duration also has an effect on the per­ ception of loudness, as shown in Figure 2.15 for a pure tone. Here we can see that once the sound lasts more than about 200 milliseconds then its perceived level does not change. However, when the tone is shorter than this the perceived amplitude reduces. The perceived amplitude is inversely proportional to the length of the tone burst. This means that when we lis­ ten to sounds which vary in amplitude the loudness level is not perceived significantly by short amplitude peaks, but more by the sound level aver­ aged over 200 milliseconds. — David Howard, Jamie Angus, coustics and Psychoacoustics, 645

Categorization

• DEFINE: Clarifies the psychophysical distinction between a sound event’s physical properties and the resulting auditory attributes.
• XREF: Directly connects to the reader’s interest in how sound mechanics produce perceived phenomena; useful companion to the earlier chapter material on SPL and SIL. — connects to: Loudness, measured in sones, depends inherently on frequency content — Almo Farina, Soundscape Ecology: Principles,…, 982
• corroborated: 3 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 858; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 623; David Howard, Jamie Angus, coustics and Psychoacoustics, 645