The Psychological Properties Of Sound

Kelvin Sholar

Sound has two types of properties or qualities which belong to it. They are either physical properties or psychical. Psychical properties of sound is another name for psychological properties or qualities related to things perceived through the mind.

There are several psychological properties of sound; including pitch, loudness and timbre. Pitch is the psychical form of the frequency of sound pressure changes. The perception of pitch depends on several related factors. First, the perception of pitch depends on what range that the frequency of the sound pressure wave is in. Second, the perception of pitch depends on how loud the sound is. Finally, the perception of pitch depends on how many other frequencies occur at the same time.

Loudness is the psychical form of the amplitude of sound pressure intensity. The perception of loudness is like the perception of pitch, because it depends on what range the sound pressure wave frequency is in, and it depends on how many other frequencies occur at the same time.

In order to understand timbre, we have to understand pure pitch; but what is that? If one strikes a tuning fork, then it produces a pure pitch. The mathematical form of a pure pitch is a sine wave. The tuning fork produces one pure pitch at a time, but when one plays the violin, then the sound that is produced is full of different pure pitches that occur at the same time. These pure pitches are represented mathematically as various sine waves but in different phase relationships. Now, timbre corresponds to a combination of frequencies that make up a sound, as well as, the overall waveform of the sound pressure wave. The violin has the timbre it has because whenever a vibration is produced by the strings of the violin, then natural sympathetic vibrations occur in the body of the violin. These sympathetic vibrations are the multiples of the fundamental frequency of the produced waveform. The more resonant an instrument is, then the more pure pitches (i.e. harmonics or overtones) that are present in its sound – and the richer the timbre of the instrument is. Ultimately, this is why the violin has a much richer timbre than a tuning fork.