Chapter 19 - Sound perception: Timbre, loudness, and pitch

Abstract

The physical sound is characterized by its partials, its amplitude, and its frequency; these correspond to the perceived timbre, loudness, and pitch, respectively. “But, to a smaller extent, frequency also contributes to loudness, and amplitude and partials also contribute to the perceived pitch.” Given these complications, and the fact that loudness is perceived logarithmically, there is a need to distinguish clearly between the physical sound intensity level commonly called volume and measured in decibels, abbreviated dB, and the perceived loudness, measured in phons. Equal loudness curves show that the human ear's sensitivity to different frequencies is far from flat, thus, in the audible range from 20 to 20,000Hz, all people are most sensitive to the midrange frequencies 1000–6000Hz, less sensitive to higher frequencies, and much less sensitive to lower frequencies. This is why you need tweeters, woofers, and subwoofers in a sound system. At high sound intensity levels, such as 100dB, the ear's sensitivity is almost flat at all frequencies, thus the music sounds better, and that is why rock concerts are always so loud, and many people enjoy loud music also when they listen through earbuds.