Shielding Effect for Sonic Boom of Projectiles
In a preceding paper  a prediction model for sonic booms of projectiles has been presented. In that model the trajectory of the projectile is conceived as a coherent line source, approximated by a series of point sources for the calculation algorithm. The sound pressure at a receiver point is obtained as the phase sensitive addition of the contributions from the individual point sources. To study the effects of barriers on the sonic boom of projectiles, the propagation calculation of the model has now been supplemented by a shielding attenuation. The conclusions gained by studying the simulation results were used to derive a simplified method to calculate the shielding effect for sonic booms. This model is based on the concept of Fresnel zones and considers three contributions to the sound pressure at the receiver point, namely the contribution over the barrier and two additional contributions which stem from segments of the trajectory to each side of the barrier. To validate the calculation methods, measurements were carried out in situations with a shielding effect ranging from 0 dB to 20 dB. The results agreed well with those of the original and the simplified prediction models. Furthermore, the measurements verified the above mentioned concept that three signal packets are responsible for the resulting sound pressure. A comparison of the spectra with and without the barrier revealed that to a first approximation, shielding does not influence the spectrum. This can partly be explained, but requires further investigation.
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Document Type: Research Article
Publication date: January 1, 2001
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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