THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

PrefaceThe science of acoustics deals with the creation of sound, sound transmissionthrough solids, and the effects of sound on both inert and living materials. As amechanical effect, sound is essentially the passage of pressure fluctuations throughmatter as the result of vibrational forces acting on that medium. Sound possessesthe attributes of wave phenomena, as do light and radio signals. But unlike itselectromagnetic counterparts, sound cannot travel through a vacuum. In SylvaSylvarum written in the early seventeenth century, Sir Francis Bacon deemed soundto be “one of the subtlest pieces of nature,” but he complained, “the nature of soundin general hath been superficially observed.” His accusation of superficiality fromthe perspective of the modern viewpoint was justified for his time, not only foracoustics, but also for nearly all branches of physical science. Frederick V. Hunt(1905–1967), one of America’s greatest acoustical pioneers, pointed out that “theseeds of analytical self-consciousness were already there, however, and Bacon’slibel against acoustics was eventually discharged through the flowering of a clearercomprehension of the physical nature of sound.”Modern acoustics is vastly different from the field that existed in Bacon’s timeand even 20 years ago. It has grown to encompass the realm of ultrasonics andinfrasonics in addition to the audio range, as the result of applications in materialsscience, medicine, dentistry, oceanology, marine navigation, communications,petroleum and mineral prospecting, industrial processes, music and voice synthesis,animal bioacoustics, and noise cancellation. Improvements are still being madein the older domains of music and voice reproduction, audiometry, psychoacoustics,speech analysis, and environmental noise control.This text—aimed at science and engineering majors in colleges and universities,principally undergraduates in the last year or two of their programs and graduationstudents, as well as practitioners in the field—was written with the assumption thatthe users of this text are sufficiently versed in mathematics up to and including thelevel of differential and partial differential equations, and that they have taken thesequence of undergraduate physics courses that satisfy engineering accreditationcriteria. It is my hope that a degree of mathematical elegance has been sustainedhere, even with the emphasis on engineering and scientific applications. Whilethe use of SI units is stressed, very occasional references are made to physicalvii