Since the 2 nd World War, many governments have continued to invest in the design of supersonic aircraft. During the piloting of the latter, it is common to hear noises of explosion. The phenomenon behind these is the sound barrier . What should we understand about this phenomenon? All the answers are in the rest of this article.

Wall of sound: what is it?

The sound barrier is an imaginary boundary that marks the point at which a supersonic aircraft moving through the air produces shock waves so strong that they can be heard on the ground . But what exactly happens when an airplane breaks the sound barrier?

As it approaches Mach 1 (about 1,235 km/h), air pressure builds up in front of the plane until it eventually overcomes drag and pushes the plane forward faster than the sound itself can travel. This creates a shock wave of compressed air that extends behind and around the aircraft like a cone.

At speeds above Mach 2, this cone becomes more pointed, as areas of high pressure move away from the aircraft faster than areas of low pressure.

How is this phenomenon explained?

Contrary to what one might think, the phenomenon that occurs during a sound barrier is quite simple. Indeed, when a mobile object moves at the speed of sound in a fluid, a phenomenon of concentration of suppression waves is recorded. The latter generates a shock wave.

For example, when a fighter plane flies, it puts pressure on the air. Under the effect of this pressure, the molecules making up the air move back and forth over each other at a speed of 340 m/s (this is the speed of sound). Once this speed is reached, the air going in one direction does not have time to return. Which then forms a ball of air on the nose of the fighter plane. It is precisely this that constitutes the wall of sound. When this ball of air explodes, you will hear a “Sonic Boom” or a “Double Bang”.

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What is the origin of the expression “wall of sound”?

The expression “sound wall” has a rather special historical significance. Indeed, technological advances in the field of aviation during the Second World War experienced a considerable rebound. This happens precisely when the planes reached certain speed limits.

The pilots were faced with problems of instability and hardening of the controls of the plane. This phenomenon so embarrassed airmen during World War II that they came to call it the “sound barrier”.

The main originator of this term is WF Hilton , a British engineer of the 1940s. However, the phrase was not banished in order to offer a pictorial description of a sudden increase in resistance.

Who is the first driver to break the sound barrier?

The famous Chuck Yeager was the first pilot to break the sound barrier on October 14, 1947 . He was aboard the Bell X-S1 fighter plane which reached Mach 1.06 , or about 1,308 km/h.

Since then, many other aircraft have exceeded Mach 1. However, it is not just about reaching supersonic speed; an aircraft must also be designed and flown correctly in order to break the sound barrier without damage. Indeed, many pilots have died attempting to break the sound barrier due to structural failure or control issues.


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