Respuesta :

The correct answer among the choices is the second option. The speed of an object traveling below the speed of sound is called a subsonic. This type of speed  is any speed operating below the speed of sound. The units used to measure this is the Mach number.

Answer:The speed of an object traveling below the speed of sound is called Subsonic .

Explanation:

Infrasound: These are the sound waves with frequency less than the 20 hertz.Sound waves with lower frequencies which are below the lower limit of human audibility.

Subsonic : Speed of an object less than the speed of sound with sound propagating medium..

Ultrasound : These are the sound waves with frequency upper than the 20,000 hertz.Sound waves with higher frequencies which are above the upper limit of human audibility.

Supersonic : Speed of an object greater than that of the speed of sound.