Sonic Booms – Another Source of Noise Exposure?

In 1953, Chuck Yeager broke the sound barrier, achieving a speed of 1,650 miles per hour and an altitude of over 90,000 feet. This historic feat introduced the world to sonic booms, the thunderous noise produced when an aircraft or aerospace vehicle exceeds the speed of sound.

Sonic booms have since fascinated audiologists and impacted communities near testing ranges. This article delves into the causes of sonic booms, their effects on humans and structures, and the public’s perception of these powerful acoustic phenomena.

Understanding Sonic Booms

When an object moves through the air at supersonic speeds, it displaces the surrounding air molecules with great force, forming a shock wave similar to a boat’s bow wave. The displaced air molecules create a cone-shaped region of pressurized air, known as a shock wave, that extends from the aircraft to the ground. As this cone spreads along the flight path, it generates a continuous sonic boom across its base.

The sharp release of pressure after the buildup by the shock wave produces the thunder-like sound known as the sonic boom. It is important to note that sonic booms occur when an observer’s ears intersect the edge of the pressure cone, rather than when the aircraft breaks the sound barrier, as commonly misconceived.

Effects of Sonic Booms

Sonic booms can be incredibly loud, reaching up to 136 decibels or 120 pascals (in pressure units) for commercial supersonic transport planes (SST). Research conducted by NASA and other institutions has explored the effects of sonic booms on humans and animals. Startle responses, disruption of ongoing activities, and disturbance of sleep and rest have been observed as common reactions to sonic booms.

The effects of sonic booms are typically measured in pounds per square foot (psf) of overpressure, with minor damage to buildings and glass occurring between 2 and 5 psf. However, structural damage is unlikely until overpressures exceed 11 psf. Severe damage to eardrums may occur at 720 psf, and lung damage would require overpressures of 2,160 psf.

Typical overpressure of aircraft types that create sonic booms are:

• SR-71: 0.9 lb, speed of Mach 3, 80,000 feet
• Concorde SST: 1.94 lb, speed of Mach 2, 52,000 feet
• F-104: 0.8 lb, speed of Mach 1.93, 48,000 feet
• Space Shuttle: 1.25 lb, speed of Mach 1.5, 60,000 feet, landing approach

Public Perception and Acceptance

The public’s tolerance and acceptance of sonic booms are influenced by various factors. Attitudes toward the source of the booms, concerns about wildlife impact, negative perceptions of the military, and living in rural areas with more pronounced noise all play a role in shaping individuals’ willingness to endure sonic booms.

NASA researchers have found that sonic booms are disruptive, annoying, and can lead to sleep disturbances. The question of public tolerance for sonic booms remains unresolved until low-sonic-boom aircraft development progresses, allowing real-world tests to gauge public reactions.

Currently, sonic booms are prohibited over the United States.

Sonic Booms and the Future

Sonic booms, the thunderous noise produced when an aircraft exceeds the speed of sound, have intrigued audiologists and impacted communities near testing ranges. Understanding the physics behind sonic booms, their effects on structures and humans, and the public’s perception is crucial. While research has shed light on the startle responses, disruption of activities, and disturbances of sleep and rest caused by sonic booms, the question of public tolerance remains.

As the development of low-sonic-boom aircraft progresses, further studies and real-world tests will shape our understanding of and response to these powerful acoustic events. While sonic booms are infrequent in the United States, they continue to be of interest in other countries where such booms are more prevalent.

So…..Is the sonic boom another source of noise exposure?   Probably not, as it is a rare impulse noise that we do not hear over the US, but could be of interest in other countries where these “booms” are more frequent.

 

References:

Armstrong Fact Sheets:  Sonic Booms.  National Aeronautical and Space Administration. Retrieved May 13, 2015:  https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-016-DFRC.html#.VVNSs_lViko

Cunningham, A., Sonic booms and human ears:  How much can the public take?  Popular Science.  Retrieved May 13, 2015: https://www.popsci.com/military-aviation-space/article/2004-07/sonic-booms-and-human-ears?image=0

Rylander, R. (1974). The Sonic Boom -Effects on humans. Sozial-Praventivmedizin.  19 (3),pp.217-.  Retrieved May 13, 2015: https://link.springer.com/article/10.1007%2FBF01999428#page-1