Acoustic sagas. How the person tamed an echo? Present
: you in the huge hall. Around you - outer darkness. Though... wait a moment, how in complete darkness you learn that you in the huge hall, but not in a small room? There is no task more simply, you will tell. Also you will be right. The sound of your voice will prompt you scales of the room in which you are. Without moving a little, you do a short and sharp hail. The rolling rumble of an echo in reply does not leave doubts - you in the big room.
Here we also approached closely one more property of a sound - ability to be reflected. The general regularity of reflection of a sound is simple and similar to properties of light waves. This phenomenon is observed on border of two environments and is one of ways of further following of a sound wave after hit on this border. If density of two environments considerably differs, then the sound wave at hit on an environment surface with a high density is almost completely reflected back at an angle, equal to a hade.
However not all waves, getting on a surface of the firm environment, are reflected. The part of them is absorbed by this material. Repeated reflections lead to fast absorption of a sound. Therefore at hit of a sound on the porous material possessing the developed and difficult structure of a surface there is its almost full absorption. You remember unusually ringing voice rumble in the empty room. But if to close a floor and a wall carpets, then the rumble will come to naught. Decrease in effect of reverberation (such scientific name received an echo in relation to the enclosed space) that will be stronger, than we will use more dlinnovorsovy carpets and than we will cover the big area of walls and a floor with them.
Production rooms in which strongly rustling equipment works, thus, could be carpeted. It would lead to decrease in noise load of hearing of workers. In reality various devices shielding, rejecting, disseminating, absorbing a sound are used to ear protection on production. Similar examples of undesirability of reverberation are single. The mankind learned to use an echo with advantage long ago.
Acoustic decisions in architecture of medieval cathedrals strike with grandeur of the sound rising up. The body sounding in them creates the inexpressible atmosphere of solemnity and awe among listeners. Terrestrial disorders sink in the all-consuming waves which are rolled, apparently, from everywhere, even from within you. Perhaps, it is one of the most ancient and most beautiful tasks which was assigned by the person to an echo.
The present did not leave an echo alone. Properties of reflection of a sound are very widely used in technology, medicine, sea navigation and other areas of human activity.
Not for nothing, though for fun, physicians call the device of ultrasonography (ultrasonic research) “ the third eye of the doctor looking in an organism “. The remarkable method of diagnostics of internals of the person based on different reflection of ultrasound by different fabrics is adopted by world medicine already more than half a century. At the beginning of 50 - x ultrasonic research was offered to of the last century the American scientists as an alternative x-ray at researches of a brain. Research by ultrasound less dangerously and does not demand expenses of forces and time in comparison with x-ray.
The area of ultrasonic researches in medicine is very extensive. Ekhoentsefalografiya - a research method, irreplaceable when determining the place of a cerebral hemorrhage at serious injuries of the head. Ultrasonic research practically of all internals, except intestines (from - for contents of gases in it) plays an important role at statement of the diagnosis today. Advanced devices ultrasonography are widely used when carrying out echocardiographic researches at which heart becomes object. The pleasure of appearance of the kid in a family seldom does without prenatal diagnostics of a fruit today. Ophthalmologists apply ultrasonic probes at determination of the sizes of an eye and the provision of a crystalline lens.
Echolocation, one may say, was borrowed and transferred to equipment by the person from wildlife. The principle of reflection of a sound from an obstacle is used in fauna in the absence of organs of vision or in conditions when visual orientation in space is complicated or it is impossible. Bats, dolphins, shrews use biological ekholokatsionny mechanisms for obtaining information on world around.
Thanks to the fact that water carries remarkably out a sound research of underwater objects by means of echolocators became the main method of determination of depth, a ground relief, location of large schools of fishes and any other underwater objects, including the ships, submarines, etc. The question of application of sound waves for receiving and information transfer about underwater objects celebrates century anniversary this year.
Ultrasonic defectoscopy - a method of definition of the latent defects in firm environments. On February 2, 2008 80 years from the moment of issue of the patent for the device of ultrasonic defectoscopy to the young scientist Sergey Yakovlevich Sokolov who became subsequently professor of the Leningrad electrotechnical institute are executed. He by right is considered the father of this method of nondestructive control which is based on reflection of a sound from the defects which are contained in the volume of solid bodies.]