The auditory (sound perception) aspect - Speech sounds may also be analyzed from the point of view of perception. The perception of speech sounds involves the activity of our hearing mechanism, which can be viewed in 2 ways.
On the one hand, it is a physiological mechanism which reacts to acoustic stimuli: the human ear transforms mechanical vibrations of the air into nervous stimuli and transmits them to the brain. The listener hears the acoustic features of fundamental frequency, formant frequency, intensity and duration in terms of 4 perceptible categories of pitch, quality, loudness and length.
On the other hand, it is also a psychological mechanism which selects from the great amount of acoustic information only that which linguistically significant.
