Preface to the second edition
Since the first edition was published 7
years ago, my coauthor Leo Beranek has sadly passed away. Thankfully though, he lived long enough to not only contribute new material to the first edition but also to see its publication. His original 1954 book ‘Acoustics’, which still forms a substantial part of this edition, made an invaluable contribution to the field of electroacoustics and inspired many subsequent authors, including the current one. For example, it was the first book to show the electrical, mechanical and acoustic radiation impedances of a transducer on the same analogous circuit.
In this second edition, I have endeavored to stay faithful to his vision. For instance, he expressed surprise that I had not written anything about electrostatic loudspeakers, so this edition includes a new Chapter 15 devoted entirely to the subject. Preceding that is a new Chapter 14, which covers vibro-acoustics, including membranes, plates, and shells. Hence the new book title: ‘Acoustics: Sound Fields, Transducers, and Vibration.’ This replaces the old Chapter 14 on state variable analysis which, according to data from digital libraries, was the least viewed and so it has been removed to make space for the new one without the book becoming too unwieldy.
There are revisions throughout, many of which have been suggested to me by diligent readers whom I have listed in the acknowledgments section. There are too many changes to list here, but the following are particularly pertinent:
Chapter 3: This contains a new section on analogous circuits for 2-port networks.
Chapter 4: The mass and resistance end corrections for a perforated sheet have been updated according to a recent paper by Xianhui Li.
Chapter 7: The field inside a closed-box or bass-reflex loudspeaker enclosure is now described with circular apertures instead of square/rectangular ones, which simplifies the equations and is truer to most real-world applications.
Chapter 13: Equations for the radiation characteristics of a rigid disk in a circular baffle or free space and the resilient disk or rectangular piston in an infinite baffle are simplified as a result of recently published work. The mutual radiation impedance between pistons in an infinite baffle now allows for pistons of different radii.
I hope that, through this edition, Leo’s legacy continues to be relevant to readers into the 21st century.
Tim Mellow 2019
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