Sonic boom and the "rise time" of the shock which makes the boom seem louder. On most aircraft designs the characteristic distance is about , meaning that below this altitude the sonic boom will be "softer". However, the drag at this altitude or below makes supersonic travel particularly inefficient, which poses a serious problem. The pressure from sonic booms caused by aircraft often are a few pounds per square foot. A vehicle flying at greater altitude will generate lower pressures on the ground, because the shock wave reduces in intensity as it spreads out away from the vehicle, but the sonic booms
Piston effect sound. Instead, tunnel boom results from the structure of the tunnel preventing the air around the train from escaping in all directions. As a train passes through a tunnel, it generates compression waves in front of it. These waves coalesce into a shock wave that generates a loud boom when it reaches the tunnel exit. The strength of this wave is proportional to the cube of the train's speed, so the effect is much more pronounced with faster trains. Tunnel boom can disturb residents near the mouth of the tunnel, and it is exacerbated in mountain valleys where the sound