Silence

The silence of nature, contrasting with the noise of the metropolis

Silence , silence ^[1] - state of calm ^{[ clarify ]} sound , also called silence ^{[2] [3] [4]} .

Sometimes in allegories silence is not called the complete tranquility of the sound environment, but only partial, relative, for example, the silence of nature , contrasting with the loud noise of the metropolis .

Silence is good for your health , therefore it is recommended that emaciated and sick people avoid too loud sounds. For children, silence is also good for a restful sleep , as too loud noises prevent the child from falling asleep. However, sounds of not too high volume (20-60 dB ) positively affect a person at any age.

The complete absence of any acoustic noise and sound is called absolute silence . It can only be recorded by instrumental studies. A person cannot hear absolute silence by hearing , because, in any case, he will hear the sound of his heart and the flow of blood through the blood vessels. In conditions close to absolute silence, a person experiences negative effects on the psyche, possibly before the appearance of auditory hallucinations in him ^[5] .

Very quiet places are sound chambers and anechoic chambers created for research and training of astronauts. For example, such cameras exist in the “Tower of Silence” ( St. Petersburg ), designed by architect A. A. Poleshchuk with the money received by academician Ivan Petrovich Pavlov from the “ Ledenzovsky Society, ” in 1913-1917. ^{[6] [7]} , now at the Museum of the History of the Research Institute of Experimental Medicine, they are the first sound chamber cameras in Russia ^[8] .

The conditions closest to absolute silence were created by Steven Orfield in South Minneapolis in the Anechoic Test Chamber of the Orfield Laboratories, designed to measure acoustic noise. To achieve exceptional silence, the room uses meter-thick fiberglass acoustic platforms, double walls made of insulated steel and concrete 30 cm thick. The camera blocks 99.99 percent of external sounds and absorbs internal ones. It is listed in the Guinness Book of Records as the quietest place; on January 21, 2004, a record low background noise indicator was recorded here: -9.4 dB ^[9] . This camera is used by many manufacturers to test the volume of their products, such as heart valves, the sound of a mobile phone display, the sound of a switch on the car dashboard. It is also used to determine sound quality ^[10] .