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Acoustics of Enclosures
Published in Malcolm J. Crocker, A. John Price, Noise and Noise Control, 2018
Malcolm J. Crocker, A. John Price
All of the analysis presented so far in this chapter has been based on the concept that sound waves can exist as energy packets that travel through the room and contribute to the reverberant sound field in a particular statistical manner. This approach is generally known as geometric or ray acoustics. Although this approach is often able to provide useful information, it cannot provide a complete explanation of the behavior of sound in an enclosure. An alternative approach, wave acoustics, is based on a study of the natural modes of oscillation of the room. The appropriate wave equation is written and solved for the particular room and initial time boundary conditions. As long as the enclosure is simple in shape (i.e., a rectangular box, shell, or tube, etc.) then the exact solution can be obtained and it will describe both the transient and steady-state behavior of the sound field.
Structural damage detection using time domain responses and an optimization method
Published in Inverse Problems in Science and Engineering, 2019
S. M. Seyedpoor, A. Ahmadi, N. Pahnabi
Civil engineering structures, during their service life, may experience damage caused by various sources such as harsh environmental conditions, overloading, ageing materials or inadequate maintenance. In order to prevent catastrophic failure and prolong the service life of the structures, early and reliable damage identification is necessary. In engineering practices, damage detection methods are categorized into two major groups as destructive and non-destructive methods. In general, the destructive methods due to their disadvantages are not appropriate; therefore, the use of non-destructive methods has attracted much attention. The non-destructive damage detection methods, which are restricted to local observations in a limited area, when applied to large structures, are very time consuming and expensive. The stress wave, ultrasonic, X-ray, acoustics and radiography are the examples of these methods. In contrast, vibration-based damage detection methods are global non-destructive ones based on the principle that the damage changes the physical properties leading to altering dynamic properties of a structure. Therefore, by utilizing the dynamic characteristics from the structural vibration, damage can be predicted.