Page 57 - Summer 2015

umes from a few cubic meters to a few hundred cubic me- ters.” Thus, “rooms as diverse as car cabins and small lecture rooms, reverberation and anechoic chambers might fit the description.” The book therefore excludes large auditoria, performance spaces, industrial buildings, etc. It discusses room acoustics; it does not discuss building acoustics (e.g., room-to-room transmission).
This book contains 491 pages and 14 chapters. The book begins with chapters on the basic properties of, and phys- ics related to, sound and sound in enclosures, such as sound pressure, acoustical impedance, and solutions to the wave equation for various boundary conditions. Further chapters discuss absorption and diffusion, and then human hear- ing and psychoacoustics—the human perception of sound. Then, the content becomes more specific to small rooms in chapters on sound reproduction, low-frequency sound fields, geometric acoustics, and rooms for music practice. The final two chapters focus on room-acoustical modeling and measurement.
[M.H. reviewed this book as a senior acoustics professor who teaches engineering acoustics to undergraduate and gradu- ate students, and who does research, mainly in architectural acoustics from engineering and physics perspectives, with a strong interest in how sound in rooms affects the health, well- being, communication, and productivity of the occupants.]
What are the book’s strengths; what is it good for? The book is well-written and organized, with many useful illustrations and extensive references. It is a comprehensive review of the state of the art on many important topics in small-room acoustics, presented by authors with much knowledge and practical experience. It discusses small rooms from both ob- jective and subjective points of view. It is a compilation of conventional and less conventional material. The introduc- tory chapters are fairly conventional, but introduce relevant correlation functions, convolution, and sound intensity. The chapter on room sound fields focuses on diffuse fields, but discusses the characteristics of non-diffuse fields. The chap- ter on sound diffusion and diffusers includes a brief dis- cussion of volume scattering; does the book ever say that scatterers reduce reverberation, independent of absorption effects? The section on scattering and diffraction in the chapter on geometric acoustics is welcome. The brief chapter on the ear (i.e., the human auditory system—I was surprised to meet this in the middle of the book) discusses its physical response characteristics and head-related transfer functions (HRTFs). The chapter on psychoacoustics helped me con- solidate my understanding of room acoustics from the occu-
pant perspective, but I wondered what my psychologist post-doctoral fellow would think of it (see below). Chapter 8 is a very useful, less conventional, review of spatial hear- ing, including the precedence effect, cocktail-party effect and spaciousness, as well as the effects of reverberation. As a researcher who does not focus on rooms for music, Chapters 9 (on sound–music, not speech–reproduction) and 10 (on sound-field optimization, including active control) helped me upgrade my knowledge of this subject. Chapter 9 intro- duces the modulation transfer function in application to loudspeakers and music. It discusses early reflections (but not early-to-late energy fractions), the effects of the replay loudspeaker, and stereo, binaural, and surround-sound re- production. Chapter 11 on rooms for sound reproduction discusses the designs of recording studies and home lis- tening rooms; the theme of Chapter 12 is music rehearsal and practice rooms, ending with a very brief discussion of rooms for speech. These somewhat unconventional sections are very comprehensive in their discussions of major de- sign issues such as room geometry and diffusion, and bring together a lot of relevant practical information. The final two chapters provide a comprehensive review of low- and high-frequency prediction and measurement methods used in room-acoustical research and design, including less con- ventional topics such as scale modeling, numerical methods, and auralization for prediction, as well as particle-velocity and sound-intensity measurement, the principle of reciproc- ity, and, briefly, binaural recording and listening tests.
What are this book’s shortcomings? It is a summary of the authors’ knowledge of the aspects of architectural acoustics that they are interested in, have studied, and applied—that is, mainly rooms for music—not a thorough treatment of all relevant topics. There are missing topics, some of them highly relevant today, such as classrooms, small open offices and industrial workrooms, speech intelligibility, early/late energy fractions, reverberation rooms, the Lombard effect, edge diffraction, sound-masking systems, “green” build- ings, etc. The book is a review of existing knowledge; some data is taken from old, unsubstantiated, sources; apparently no new work was done specifically for this book to make it more complete. Some topics are introduced, then dismissed in one or two brief, conceptual paragraphs that do not say much, but may provide useful references; maybe these top- ics will be expanded in the second edition. The book’s index could be more comprehensive; for example, the preface says that the book is relevant to reverberation rooms, but I found little on this topic, and it was not listed in the index.
Summer 2015 | Acoustics Today | 55