Define Mach number. Distinguish between Ultrasonic, subsonic, supersonic, and hypersonic waves.

2. b) Define the Mach number. Distinguish between Ultrasonic, subsonic, supersonic, and hypersonic waves.

Answer:

Mach number: Mach number is defined as the ratio of the speed of the object to the speed of sound in the
given medium

Mach number = Object speed/speed of sound in the medium
M=v_o/v_s

Ultrasonic waves: Ultrasonic waves have frequencies of more than 20 kHz. The human ear is not sensitive to these waves. They travel at the same speed as that sound. The amplitude of the ultrasonic wave is also small.

Subsonic wave: If the speed of a Mechanical wave or object moving in the fluid is lesser than that of sound, then such a speed is referred to as subsonic and the wave is a subsonic wave. All subsonic waves have Mach no. < 1.

Supersonic wave: Supersonic waves are mechanical waves that travel with speeds greater than that of sound. Mach no.> 1.

Hypersonic wave: In the supersonic range, when Mach no > 5 means is called a hypersonic waves.