Diffraction of sonic booms around buildings resulting in the building spiking effect

• Published in: The Journal of the Acoustical Society of America Vol. 129; no. 3; pp. 1250 - 1260
• Main Authors: Cho, Sang-Ik T., Sparrow, Victor W.
• Format: Journal Article
• Language: English
• Published: Melville, NY Acoustical Society of America 01-03-2011; American Institute of Physics
• Subjects: Acoustics; Aeroacoustics, atmospheric sound; Aircraft; Buildings; Computer Simulation; Diffraction; Exact sciences and technology; Facility Design and Construction; Fundamental areas of phenomenology (including applications); High-Energy Shock Waves; Impulse response; Linear Models; Mathematical analysis; Mathematical models; Motion; Noise, Transportation; Nonlinear acoustics, macrosonics; Numerical Analysis, Computer-Assisted; Physics; Pressure; Sonic booms; Sound Spectrography; Spiking; Time Factors; United States; United States National Aeronautics and Space Administration; United States; Aeroacoustics; Non linear acoustics; Sonic boom
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.3543984

The diffraction of a sonic boom around a building of finite dimensions yields amplification of the front shock and a positive spike that follows the tail shock in the pressure waveform recorded at the incident side of the building's exterior surface. This physical phenomenon is consistently found both in the data obtained from a 2006 NASA flight test and field experiment, and in the finite-difference time-domain simulation that models this particular experiment, and the authors call it the "building spiking" effect. This paper presents an analysis of the numerical and the accompanying experimental results used to investigate the cause of this effect. The simulation assumes linear acoustics only, which sufficiently describes the physics of interest. Separating the low and high frequency components of boom recordings using optimal finite impulse response filters with complementary magnitude responses shows that the building spiking effect can be attributed to the frequency dependent nature of diffraction. A comparison of the building spiking effect of a conventional N-wave and a low-amplitude sonic boom shows that a longer shock rise time leads to less pronounced amplification of the exterior pressure loading on buildings, and thus reveals an advantage of shaping a boom to elongate its rise time.