Pitch Discrimination

As I have discussed in a previous post, we are able to distinguish sounds with a subjective quality called pitch. Most people are able to easily identify the notes of a bass as low and the notes of a piccolo as high. The physical property of sound that differentiates these instruments is the frequency of the sounds that they produce. Soundwaves with higher frequencies are perceived to have a higher pitch, and the opposite is true for soundwaves with lower frequencies. While you may know that the general range of hearing for humans is 20-20,000 hertz, how are we able to differentiate sounds that differ in frequency? The answer lies within the concept of pitch discrimination.

As I mentioned in my previous post, the fundamental part of the ear that allows humans to differentiate the pitch of sounds is the cochlea, and hair cells in the cochlea are able to convert sound energy to nerve signals that the brain can perceive. The problem with this lies in the brain's differentiation of nerve signals sent to it by the cochlea as "all nerve impulses are alike"(The Physics of Music and Color). The two things that differentiate nerve impulses are the specific hair cells that transmit the signal and the pattern of impulses over time. Scientific evidence suggests that the brain utilizes both of these aspects in processing pitch discrimination. The theories that explain these different approaches respectively are the Place Theory of Pitch Perception and the Rhythm Theory of Pitch Perception.

The Place Theory of Pitch Perception can be explained with hair cells. Effectively, different hair cells correspond to different frequencies because of how sound passes through the ear. Certain hair cells are triggered by sounds of specific frequencies. Because the brain is able to distinguish specific hair cells, it is able to create pitch discrimination.

The Place Theory of Pitch Perception is often considered incomplete, because it is not able to account for how sensitive the human ear is to slight changes in pitch. For this reason, the Rhythm Theory of Pitch Perception is often considered to occur simultaneously. According to this theory, the brain is able to interpret different patterns of vibrating hair cells triggered by sound waves of different frequencies in order to create pitch discrimination.

Works Cited:

1.  Gunther, Leon. The Physics of Music and Color. New York, New York: Springer, 2012.