Answer:
Speed of sound
Explanation:
The sound barrier or sonic barrier is the sudden increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. Therefore, sound barrier and speed of sound are synonyms. In dry air at 20 °C (68 °F), the speed of sound is 343 meters per second (about 767 mph, 1234 km/h or 1125 ft/s).
