The term "Barong Barong" might bring visions of dragons or mythical creatures to mind, but in reality, it refers to a distinct noise pollution issue in the aviation industry. The term is a onomatopoeia, coined from the sound it describes, and has become synonymous with the sonic boom phenomenon caused by aircraft. In this article, we'll delve into the essence of Barong Barong, explaining what it is, its impacts, and the efforts being made to mitigate it.
Sonic booms, commonly known as "Barong Barong" in Philippines, are produced when an aircraft exceeds the speed of sound, creating concussive air pressure waves. These sound waves can be heard as a deep thunder-like clap or rumble, hence the name "Barong Barong," which is Filipino for "rumble rumble." Let's explore this fascinating yet contentious issue further.
Understanding Sonic Booms
Sonic booms are the byproduct of a physical phenomenon. When an object moves through the air faster than the speed of sound, it causes a series of pressure disturbances that spread out in a cone, similar to how the wake of a boat spreads out behind it. For aircraft, this critical speed is about Mach 1, or 1,225 kilometers per hour (765 miles per hour) at sea level.
These pressure disturbances hit the ground and other surfaces at the same time, creating a shock wave that manifests as a sonic boom when it reaches the observer's ears. The sound is typically loud, sudden, and distinct, with reports of windows rattling and people feeling brief vibrations, especially with low-flying aircraft.
Sonic Boom Hassles
While sonic booms might be interesting from a scientific standpoint, they can cause significant nuisance for people living or working near airfields, military bases, or flight paths. The sudden, powerful noise can be startled, distracting, or even damaging, leading to tranquility and property damage complaints, especially during night-time operations.
A study by the UK Civil Aviation Authority found that, on average, a single sonic boom can cause around 2.2 people to seek medical advice, typically for stress or anxiety. Additionally, sonic booms can be costly, leading to increased noise-activated insurance claim payouts for aircraft operators.
Regulations and Challenges
Due to these impacts, many countries have imposed sonic boom restrictions, with most civilian aircraft tasked with maintaining speeds below Mach 1, particularly over land. The International Civil Aviation Organization (ICAO) limits low-altitude (below 10,000 meters) supersonic flight for commercial airliners over land surfaces, except in emergency situations.
The challenge lies in detecting and enforcing these limits. Measuring true supersonic speeds requires precise, expensive equipment, and some aircraft, like stealth planes, can navigate without leaving obvious audio or radar signatures. This makes clandestine sonic booms a tactic in military operations and reconnaissance missions.
Controlling Sonic Booms: Innovations Afoot
The aviation industry is actively seeking solutions to minimize or eliminate sonic booms. The key lies in reducing the shock waves generated during supersonic flight.
One approach is to design aircraft fuselages with a long, slender shape and a sharp, curved nose, altering the shock wave formation and spreading it out, resulting in a quieter boom. "Low-Boom-Forming" techniques explore this idea, with experimental aircraft like the Quiet Supersonic Technology Demonstrator (QueSST) and the Supersonic Aerodynamic Flare Testing (SAFT) project making strides in this area.
Shaped Sonic Booms
A novel concept in sonic boom management is engineering the shock waves to produce pleasant-sounding noises. The idea, known as "shaped sonic booms," involves adjusting the shape of the aircraft to control the delay and intensity of the shock waves, making the boom less jarring and more akin to musical tones.
This approach builds on research showing that the brain processes familiar sounds, like music, differently than abrupt, jarring noises. By shaping sonic booms to sound more like natural phenomena or pleasant melodies, they could become less intrusive to human perception, potentially allowing for increased supersonic operations over land.
While the quest to tame the Barong Barong continues, with scientific advancements and innovative technologies on the horizon, the future of sonic booms appears quieter and more tolerable. As our understanding and control over supersonic flight advance, the aviation industry may soon silence the rumble, opening new avenues for air travel and exploration.