The speed at which an object, such as an aircraft, breaks the sound barrier depends on various factors, including the altitude, temperature, and the composition of the medium through which it is traveling (usually air). In general, at sea level and under standard atmospheric conditions, the speed of sound is approximately 343 meters per second (1,125 feet per second) or about 1,235 kilometers per hour (767 miles per hour).
To break the sound barrier, an aircraft needs to exceed the speed of sound in the surrounding medium. This speed is often referred to as Mach 1. So, to break the sound barrier, an aircraft would need to reach or exceed Mach 1. Mach 1 represents the speed of sound and is equivalent to one times the speed of sound.
However, it's important to note that the speed of sound is not a fixed value and can vary with altitude and temperature. As an aircraft climbs to higher altitudes, where the air is less dense and the temperature is lower, the speed of sound decreases. Therefore, the indicated airspeed required to break the sound barrier also decreases at higher altitudes.
For example, at an altitude of 11,000 meters (36,000 feet), where the temperature and air density are lower, the speed of sound is around 295 meters per second (967 feet per second) or approximately 1,060 kilometers per hour (660 miles per hour). At this altitude, an aircraft would need to reach or exceed Mach 1, which is now equivalent to 295 meters per second.
In practical terms, modern supersonic aircraft such as fighter jets and supersonic passenger jets like the Concorde were designed to break the sound barrier and achieve speeds greater than Mach 1. These aircraft can typically reach speeds between Mach 1 and Mach 3, depending on their design and purpose.