This Is Your Brain on Music: The Science of a Human Obsession

by Daniel J. Levitin

One counterintuitive point is that loudness is, like pitch, an entirely psychological phenomenon, that is, loudness doesn’t exist in the world, it only exists in the mind. And this is true for the same reason that pitch only exists in the mind. When you’re adjusting the output of your stereo system, you’re technically increasing the amplitude of the vibration of molecules, which in turn is interpreted as loudness by our brains. The point here is that it takes a brain to experience what we call “loudness.” This may seem largely like a semantic distinction, but it is important to keep our terms straight. Several odd anomalies exist in the mental representation of amplitude, such as loudnesses not being additive the way that amplitudes are (loudness, like pitch, is logarithmic), or the phenomenon that the pitch of a sinusoidal tone varies as a function of its amplitude, or the finding that sounds can appear to be louder than they are when they have been electronically processed in certain ways—such as dynamic range compression—that are often done in heavy metal music.