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Environmental Ergonomics
Published in Robert W. Proctor, Van Zandt Trisha, Human Factors in Simple and Complex Systems, 2018
Robert W. Proctor, Van Zandt Trisha
Sonic booms are examples of unpleasant noise that evoke strong emotional responses. A sonic boom occurs when an aircraft travels faster than the speed of sound. The booms occur unexpectedly, have rapid onset, and are loud enough to shake buildings and startle people. One of the most notorious studies of the effects of sonic booms on people was conducted in 1964 by the U.S. Federal Aviation Administration (FAA; Borsky, 1965). From February 3 through July 30 of that year, residents of Oklahoma City, which during the latter part included one of the authors (RWP), were subjected to eight sonic booms per day to assess the possible effects of supersonic transport flights on residents’ attitudes. Interviews were conducted with nearly 3000 persons at 11, 19, and 25 weeks after the beginning of the testing period, and complaints filed by all residents were recorded. As Gordon Bain, then Deputy Administrator for Supersonic Transport Development of the FAA, commented, “The Oklahoma City sonic boom study … was the first major effort anywhere in the world to determine the nature of public reaction to sonic boom at specified, measured levels over a reasonably extended period of time” (Borsky, 1965, p. ix).
Exhaust System
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
Supersonic airplanes produce a unique noise phenomenon: the sonic boom. In most cases, a sonic boom is experienced as a shock wave sweeping across the ground below the aircraft. However, sonic booms can also occur during acceleration periods such as diving, and in such cases are more transient. Though sonic booms are obviously much more damaging than noise produced during subsonic flight, they are generally restricted to military aircraft and are banned above most urban areas, and thus contribute less to the noise pollution experienced by most people.
Aircraft
Published in Suzanne K. Kearns, Fundamentals of International Aviation, 2021
The speed of sound is not constant, as it changes with air temperature, but on a standard day at sea level, it is 662 knots (1,225 kilometers per hour; 761 miles per hour). Therefore, as the speed of sound is not a single velocity, it is expressed as a ratio between an aircraft’s speed and the speed of sound. This ratio is called the Mach number, after Austrian philosopher Ernst Mach, and it is used to categorize aircraft types based on their maximum speed: Subsonic—Mach = < 1. This is the range that is generally used by international air transport aircraft. Aircraft generally operate at less than 0.8 Mach, as this speed range results in all airflow over the aircraft remaining lower than Mach 1.Transonic—Mach = 1. These aircraft are approaching Mach, and some points on the airframe will be less than the speed of sound, while other points will exceed it. In general, aircraft do not cruise near this speed due to high drag associated with the compressibility effect. A sonic boom is created when an aircraft attains Mach 1 (the aircraft is moving faster than the sound waves it creates, so the sound waves form a cone of sound behind the aircraft, which creates an extremely loud sound, like an explosion or gunshot). Aircraft operating through this range almost always have swept wings, meaning when viewed from above, the wings angle back in an inverted V shape.Supersonic—1Mach = > 1 through < 5. Aircraft aerodynamics beyond Mach are quite different from those in subsonic flight. As drag hits a maximum just before the speed of sound, once an aircraft accelerates past Mach 1, drag is reduced and fuel economy improves. However, because the lift-to-drag ratio is reduced, these aircraft almost always have a similar shape: a long and thin fuselage with large delta-shaped wings (that form a solid-triangle shape). High-supersonic speeds are often classified as Mach 3 - 5.Hypersonic—Mach > 5. In hypersonic flight, aerodynamic heating occurs, and aircraft must be designed to withstand extremely high temperatures. High-hypersonic speeds are often classified as 10 < Mach > 25, with space vehicle reentry speeds beyond Mach 25.
Non-Markov behavior of acoustic phase variance in the atmospheric boundary layer
Published in Waves in Random and Complex Media, 2022
Vladimir E. Ostashev, Elena Shabalina, D. Keith Wilson, Matthew J. Kamrath
Another application is to understand the effect of turbulence on pulse propagation, e.g. blast waves and sonic booms from a new generation of supersonic aircraft, which are under development. Atmospheric turbulence increases the rise time of sonic booms, while lowering their peak amplitude and elongating their tails [19]. These effects tend to make sonic booms more tolerable to people.