Acoustic sagas. As well as why we hear sounds?
It seems that we were already defined that represents a sound in air. It is a continuous stream of consolidations of air, and degree of their compaction speaks about loudness, and frequency - about sound height. How our organism distinguishes these streams?
The mechanism of acoustical perception and the biomechanic of process of perception of a sound it was completely recreated only at the end of 50 - x the last century. The enormous role in it was played by the scientist George Bekeshi ( of Bekesy, Georg Von ), it is from Hungary. X one of perpetual motion machines of progress - the claim became the beginning of its researches still in 20-.
All the matter is that hardly established those years, telephone network of Hungary served as an intermediate link in the European network. Whether it is necessary to say about what the easiest was to write off any malfunctions for not maturity of the Hungarian lines? Here then - that young George also received a task from the management scientifically - research laboratory Ministries of Communications of Hungary - to understand and establish the reason. Over time George placed everything in places. In most cases imperfection of telephone sets which membranes distorted a voice to unrecognizability was the reason of claims. The fatal conclusion caused the beginning of researches of a structure of organs of hearing by George.
Full disclosure of an essence of process of perception of a sound an ear, the break which followed it in the field of medicine and quite deserved Nobel Prize in the field of physiology and medicine in 1961 became result of researches. Thanks to George Bekeshi we will be able freely and surely, though in brief, to consider a structure and the mechanism of functioning of an ear.
The ear of the person consists of three departments. The first - the simplest - carries the name of an external ear. Its structure and functions are clear. They are entirely directed to catching of a sound. The external ear comes to the end with an eardrum.
The second department - a middle ear. Fluctuations from an eardrum are transferred to difficult system from three stones carrying the beautiful names “ hammer “ “ anvil “ and “ stremechko “. Their function - to extinguish amplitude of fluctuations, increasing their force. It is necessary precisely to transfer fluctuations to the sound accepting department of an ear - an inner ear. Strengthening of fluctuations happens thanks to the lever mechanism of work of acoustical stones. It is remarkable that the middle ear is supplied with the protective mechanism: at very high level of loudness, t. e, sound pressure, special muscles pull an eardrum, thereby extinguishing amplitude of the fluctuations given by it to acoustical stones and, as a result, protecting extremely sensitive inner ear from damage.
The main body of an inner ear is the snail. Reminding the representative of fauna in a form, the snail has complex structure. In brief we will tell that the main bodies of a snail are the membrane and voloskovy cages which are sound receptors. Fluctuations from acoustical stones pass a way through a liquid column to a membrane surface, causing its fluctuations. There are several theories of an explanation of further succession of events. According to Bekesha`s theory, the surface of different sites of a membrane possesses different physical properties. Therefore fluctuations of various frequency cause fluctuations of its various sites. That is, low frequencies cause fluctuations of one site of a membrane, and high - absolutely another. These fluctuations are also transferred to the voloskovy cages contacting to a membrane. The theory explains both frequency distinction of a sound, and division according to loudness. Than the sound is louder - that, naturally, the membrane fluctuates stronger and voloskovy cages receive more intensive signal.
Further passing of the transformed sound signal - a problem of nervous system. It should be added that there are two types of conductivity of a sound: air and bone. In usual conditions the first way of sound transmission prevails. The bone way begins to play a role, say, at immersion of the person under water. And, if at an air way of transfer the way of a sound lies through an external and middle ear, then in case of bone sound vibrations are transmitted through skull bones directly in a snail.
From features of a human ear It should be noted its greatest sensitivity to sounds with a frequency from 1000 to 3000 Hz that lies in the area of frequencies of human informal conversation. It means that with such frequency the ear perceives fluctuations at rather small levels of sound pressure.
The following remarkable feature of hearing of the person is his binauralnost . It means the property arising from paired relationship of an auditory organ. Thanks to a binauralnost, we can define the direction in which there is a sound source. Exclusive sensitivity and ideal setup of the sound analyzer allows to catch a difference in time between the sound signals which came to the left and right ear in spite of the fact that this time makes ten-thousand fractions of a second. In addition to it, the left and right ear at the asymmetrical provision of a source of a sound hear it with various loudness.]