The sound barrier


October 17, 2021

The sound barrier is, in everyday speech, a term for the speed of sound in the Earth's atmosphere. As an airplane moves through the air, pressure waves form around the airplane. As the speed of the aircraft increases, there is an accumulation of pressure waves around the aircraft. When the speed of the aircraft reaches the speed of sound, this accumulation causes a "wall" of air under high pressure around the aircraft. It is this "wall" that is called the "sound wall". At the speed of sound, the "wall" is almost flat, but as the speed of the aircraft increases, the shape of the "wall" becomes a cone, which becomes sharper the higher the speed of the aircraft. The cone shape is visible in the pictures to the right. The high - and unstable - pressure means that it is a great strain on the aircraft's construction to fly at speeds close to the speed of sound. When it is said that an airplane "breaks the sound barrier", it means that the airplane accelerates from a speed below the speed of sound to a speed above the speed of sound. The speed of sound in the earth's atmosphere at 1 bar is approximately 347 m / s. The bang caused by planes flying faster than sound is not, as many believe, a plane breaking the sound barrier. The bang is the sound barrier itself. Sound is variations in air pressure, and the sharp increase in air pressure, caused by the accumulation of pressure waves, sounds like a loud bang. The bang is strong enough to shatter windows, something many nurseries noticed, until rules were introduced such as that the Concorde passenger plane was only allowed to go supersonically over the open sea and at high altitudes. The principle of the "sound barrier" also applies not only to aircraft in the air, but to all objects that move through gases. This could be, for example, a projectile from a firearm, or a whip that strikes in a way that causes the tip to produce a sound. The first time the sound barrier was broken in a controlled, plane flight of an aircraft was on 14 October 1947. The speed of sound is not constant, so that a separate measurement system for flight speeds has been introduced, the Mach scale, where the speed of sound is Mach 1, and double the speed of sound , Mach 2, etc. Speeds below Mach 1 are called subsonic, while higher speeds are supersonic (son sound)

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