What is Sound Barrier?

The expression which is "breaking the sound barrier" simply means going faster than the speed of sound in an aircraft.

The expression which is "breaking the sound barrier" simply means going faster than the speed of sound in an aircraft.

The problem of calculating the speed of sound was first considered by Sir Isaac Newton. He attempted to measure it by checking the time lapse between the appearance of flame from distant cannon burst and the arrival of the report. However, his experiments overlooked the important factor of air temperature and density. It was 130 years later that the French astronomer, Pierre Simon de LaPlace, pointed out this error. Under standard conditions the speed of sound is now accepted to be 760 miles per hour at sea level and 660 miles per hour at an altitude of 35,000 feet.

Supersonic speeds are calculated, beginning with the speed of sound, in Mach numbers. Mach 1 stands for the speed of sound; Mach 2 is twice the speed of sound. An aircraft or ant projectile reaching Mach 1 speed forms a shock wave at its leading edge. A shock wave is a pilling-up of air or an accumulation of sound waves. The cannon-like detonation sometimes associated with breaking the sound barrier, or reaching the speed of sound, is really a shock wave generated by an airplane flying at supersonic speed. As the airplane flies on, the shock wave keeps on following the line of flight, hitting the earth with considerable force. The resulting noise from the airplane is called the sonic boom.