The speed of sound at 30,000 feet is 678.1 miles per hour (mph). This specific value is important for various applications, particularly in aeronautics, where it is used to calculate Mach numbers for aircraft flying at high altitudes.
Altitude's Influence on Sound Speed
The speed at which sound travels is not constant and varies significantly with atmospheric conditions, most notably temperature. As altitude increases, the air temperature generally decreases, which in turn causes a reduction in the speed of sound. This phenomenon explains why sound travels slower in the colder, less dense air found at higher elevations compared to warmer air closer to sea level.
Speed of Sound at Various Altitudes
To illustrate how the speed of sound changes with elevation, the table below provides data for specific altitudes:
| Altitude (Feet) | Altitude (Meters) | Speed of Sound (mph) |
|---|---|---|
| 25,000 | 7,620 | 692.6 |
| 30,000 | 9,144 | 678.1 |
| 35,000 | 10,668 | 660.7 |
As this table demonstrates, there is a clear downward trend in the speed of sound as altitude increases, reflecting the impact of changing atmospheric conditions.
Factors Influencing the Speed of Sound
The primary factor determining the speed of sound in air is temperature. Sound waves propagate through the vibration of air molecules. In colder temperatures, air molecules have less kinetic energy and are more spread out (less dense), which slows down the rate at which they transmit vibrations. While air pressure and humidity also play minor roles, temperature is the dominant factor influencing sound speed in the atmosphere.
Practical Implications of Sound Speed at Altitude
Understanding the speed of sound at different altitudes is crucial for:
- Aviation and Aerospace: Essential for designing and operating aircraft, especially those capable of supersonic flight. Engineers use this data to calculate an aircraft's Mach number (its speed relative to the speed of sound) and predict aerodynamic behavior.
- Atmospheric Research: Helps meteorologists and atmospheric scientists analyze the structure and properties of the atmosphere.
- Sonic Boom Prediction: Accurate knowledge of sound speed at altitude is necessary for predicting when and where sonic booms will occur from supersonic aircraft.
This precise data is fundamental for scientific and engineering applications where the behavior of sound waves in varying atmospheric conditions is critical.
