Hearing mechanism as well as that of equilibrium is quite complicated.

The mechanism of hearing as well as that of equilibrium is quite complicated. This is because the vibrations of the sounds cause the auditory receptors to stimulate, while the head movements disturb the fluids surrounding the balance organs. Nevertheless, the auditory organs allow us to hear a wide range of sounds, while sensitive balance receptors keep the nervous system constantly informed of the position and movement of the head.Although the organs serving these sensations are located inside the ear, their receptors respond to different stimuli and are activated independently from one another.

Thus the sounds produce air vibrations, which are transmitted to the tympanic membrane, which moves the middle ear bone. The latter exert pressure on the circulating fluid in the inner ear. The fluid movement is accompanied by the movement of membranes and cells which stimulate the surrounding neurons. Stimulated neurons generate signals that spread to the brain. The interpretation of these impulses constitutes what we call hearing.
Unlike light that can be transmitted through a vacuum, the conduction of sound requires the presence of a resilient environment. Its velocity in dry air is about 331 m / s, while its velocity in an environment does not change. On the other hand, it is larger in solid environments than in gases, which include air.

Sound is formed as a result of airborne sound waves changes and has two main characteristics:

Frequency

The wave of a pure tone is periodic, while the frequency is the number of waves passing through a given point at a given time. It is expressed in hertz (Hz). The shorter the wavelength, the greater the frequency of the sound. The range of frequencies a human can hear is from 20 to 20,000 Hz. Our ears are most sensitive to frequencies between 1400 – 4000 Hz. Within this range we can also distinguish frequencies that vary by 2 – 3 Hz.Very low frequency sounds (less than 20 Hz) create suppressive waves that travel all the way through the cochlea but do not reach the organ of the cortex. So they are below the threshold of hearing.Different frequencies of sound we perceive as differences of the timber (“color”) of sound. The higher the frequency, the thinner and sharper a sound is perceived. Most sounds perceived in everyday life are mixtures of some frequencies. This production of sound is called quality and enables us to perceive the same musical note differently when singing a soprano, and differently when listening to it from a piano or clarinet. It is the quality of sound that determines the richness or complexity of the sounds (and music) we hear.

Intensity

Intensity is an objective physical characteristic and validity of sound, and height of sound is related to our subjective interpretation of its intensity. Sound intensity is measured in logarithmic units called decibels (dB). In a clinical audiometer, the decibel rate is arbitrarily determined and starts at 0 bB, which is the hearing start for normal ears. Each 10 dB gain is associated with a 10-fold increase in sound intensity. Meanwhile, the intensity of sound that human ears can hear without pain ranges from 0.1 to 120 dB. (The pain threshold is 130 dB).Hearing loss is common in people who are exposed for a long time or continuously to sounds with intensities greater than 90 dB. This is easier to understand, given that a normal conversation takes place in the 50 dB range. In a noisy restaurant, the intensity reaches around 70 dB, while in an amplified musical environment it exceeds 120 dB.

Amplitude

The intensity of the sound is related to its energy or to the pressure difference that exists between compressed or sparse areas. Graphically, the intensity of the sound corresponds to its amplitude or the peak of the sound wave.