In details

Physiological Qualities of Sound (continued)


Intensity - is the quality that distinguishes between strong and weak sound. It depends on the amplitude of vibration: the higher the amplitude the stronger the sound and vice versa.
In practice we do not use sound intensity units, but sound intensity level units, a quantity related to the sound intensity and the way our ears react to that intensity. These units are the bel and your submultiple the decibel (dB), which is worth 1 tenth of bel.

The human ear can support sounds up to 120dB, like the blaring horn of a car. The noise produced by a jet engine a few meters from the observer produces a sound of about 140dB, capable of causing painful stimuli to the human ear.

The hustle and bustle of big cities causes the so-called noise pollution composed of the most varied noises: engines and car horns, compressed air hammers, radios, televisions and so on. Prolonged exposure to levels above 80dB has been shown to cause permanent ear damage. The intensity decreases as the sound propagates, ie the farther from the source, the less intense the sound.

Timbre - Imagine the following situation: A listener who does not understand music is in a room, next to which there is another room where there is a piano and a violin. If one person plays the C-note on the piano and at the same time another person plays the C-note on the violin, both with the same force both sounds will have the same pitch (frequency) and the same intensity. Even without seeing the instruments, the listener in the other room can easily distinguish one sound from another, because each instrument has its own distinctive sound, that is, its timbre.
Therefore, we can say that timbre is the quality that allows us to perceive the difference between two sounds of the same height and intensity produced by different sound sources.