Acoustic theory is a scientific field that relates to the description of sound waves. It derives from fluid dynamics. See acoustics for the engineering approach.
Propagation of sound waves in a fluid (such as water) can be modeled by an equation of continuity (conservation of mass) and an equation of motion (conservation of momentum) . With some simplifications, in particular constant density, they can be given as follows:
where is the acoustic pressure and is the flow velocity vector, is the vector of spatial coordinates , is the time, is the static mass density of the medium and is the bulk modulus of the medium. The bulk modulus can be expressed in terms of the density and the speed of sound in the medium () as
If the flow velocity field is irrotational, , then the acoustic wave equation is a combination of these two sets of balance equations and can be expressed as
where we have used the vector Laplacian, . The acoustic wave equation (and the mass and momentum balance equations) are often expressed in terms of a scalar potential where . In that case the acoustic wave equation is written as
and the momentum balance and mass balance are expressed as...LESS
This three-volume book gives a thorough and comprehensive presentation of vibration and acoustic theories. Different from traditional textbooks which typically deal with some aspects of either acoustic or vibration problems, it is unique of this book to combine those two correlated subjects together. Moreover, it provides fundamental analysis and mathematical descriptions for several crucial phenomena of Vibro-Acoustics which are quite useful in noise reduction, including how structures are excited, energy flows from an excitation point to a sound radiating surface, and finally how a structure radiates noise to a surrounding fluid. Many measurement results included in the text make the reading interesting and informative. Problems/questions are listed at the end of each chapter and the solutions are provided. This will help the readers to understand the topics of Vibro-Acoustics more deeply. The book should be of interest to anyone interested in sound and vibration, vehicle acoustics, ship acoustics and interior aircraft noise.
This is the third volume and presents problems and solutions plus a summary of the main results from volumes 1 and 2.