Why Do We Not Hear Sonic Booms from Aircraft Overhead?

Understanding Sonic Booms

In the 1970s, it was not uncommon to hear sonic booms if you lived in certain parts of the United States, such as West Texas. Sonic booms occur when an aircraft travels faster than the speed of sound, creating a shockwave that can produce a loud, disruptive noise. This phenomenon was most famously experienced during the heyday of high-speed supersonic flight.

The Decline of Supersonic Flight in Civil Aviation

The introduction of the Concorde in the 1970s and 1980s marked a brief period of civil supersonic flight. However, due to high operating costs, limited passenger capacity, and concerns about the sonic boom, the Concorde ceased commercial operations in 2003. Since then, no civilian aircraft have been designed or operated with the capability to break the sound barrier over populated areas.

Laws and Regulations Governing Supersonic Flight

In the United States, the Federal Aviation Administration (FAA) strictly regulates supersonic flight over land. The key regulations are found in 14 CFR § 91.817, which states the following:

No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator in accordance with §91.818. No person may operate a civil aircraft for which the maximum operating limit speed (MM0) exceeds a Mach number of 1 to or from an airport in the United States unless—Information available to the flight crew includes flight limitations that ensure that flights entering or leaving the United States will not cause a sonic boom to reach the surface within the United States,The operator complies with the flight limitations prescribed in paragraph b1 of this section or complies with conditions and limitations in an authorization to exceed Mach 1 issued in accordance with §91.818.

These regulations are designed to protect public safety and reduce complaints from citizens living in areas where supersonic aircraft might pass. They severely limit the ability of commercial and private aircraft to break the sound barrier over populated areas.

Historical Context and Lessons Learned

Before the implementation of these laws, there were instances when sonic booms were frequent. For example, in the 1950s, I lived near several aircraft factories in England, where de Havillands regularly conducted supersonic tests. These sonic booms were a regular occurrence and sounded like a very short clap of thunder. The residents of the area were accustomed to this phenomenon.

Perceived Damage to Structures

One of the more amusing stories from those days involves the perception of damage caused by sonic booms. My parents, who lived in West Texas, believed that the cracks in their fireplace at their lake house were caused by sonic booms. Although this is unlikely to be a real cause of damage, it speaks to the power of a sonic boom and its potential to create confusion among observers.

While the thunder-like sound can be startling, it is important to note that sonic booms are typically short-lived and do not cause significant structural damage. The rumble is mostly confined to a small area around the aircraft.

In conclusion, the lack of sonic booms from aircraft overhead today is a direct result of stringent regulations in place to protect the public and maintain a peaceful environment. While the Concorde and other supersonic aircraft brought technological marvels, the practical and regulatory challenges led to their limited use and eventual disappearance from civilian service.