The Bookshelf (Feb. 1979)

Music, Speech & High Fidelity by William I. Strong & George R. Plitnik. Brigham Young University Press, 1977, $9.95.

This large format (8 1/2 x 11) soft-cover book is subtitled, "A Descriptive Acoustics Worktext." At the end of each chapter are a number of exercises, lists of references and available audio-visual material, and demonstrations for classrooms. The first chapter of 40 pages covers some fundamentals of vibration. The second chapter of about the same length discusses the characteristics of sound waves.

The broad subject of the ear and hearing is handled fairly well within the 50-page space allotted. Tone timbre and spectrum, formants, critical bandwidth, and temperament are among the important topics presented. A short chapter on acoustical environments gives a non-detailed look at insulation, reverb time and absorption, properties of materials, and auditorium design. The 54-page chapter on the acoustics of speech is one of the stronger sections of this text. Speech production, phoneme classification, and the vocal tract are among the subjects not too familiar to many audio engineers that are covered in detail.

A 106-page chapter on musical acoustics amounts to a book itself on the subject. Spectral envelopes, dynamic ranges, impedance curves-good figures abound. All instrument types are covered in detail; for example, there are 16 pages just on the pipe organ. A 28-page chapter on electronic reproduction is really much too short to cover the area adequately.

There are a few short, non-detailed appendices which are elementary in nature. The book lacks an index, but there is some detail in the table of contents. At times, the approaches in the text are simple, and there are some of the most atrocious puns to ever appear in print. On the other hand, a great deal of material is presented lucidly with many excellent line drawings. The exercises are well thought out to aid the student (including the reader) in understanding fundamental relationships. This is an excellent text for introductory coverage of the acoustics of speech and music, and it provides helpful material in other areas as well.

--Howard A. Roberson

Active-Filter Cookbook by Don Lancaster. Howard W. Sams, 1975, $14.95.

Don Lancaster has written enough "cookbooks" to qualify for some sort of award in the culinary arts. This particular work starts with a discussion of the advantages and disadvantages of active filters and a section on terms and concepts. The following chapter on op-amps gives a general back ground including a design-examples page which has an eye-catching flag for immediate identification. The third chapter introduces the reader to first-and second-order networks. The author has flag-identified sections on "The Math Behind" which helps the general text flow more smoothly and, at the same time, gives the information essential to some. Amplitude and phase responses are shown for LP (low-pass), HP (high-pass) and BP (band-pass) filters.

The next two chapters cover filter responses, guiding the reader on order, selecting shapes, design criteria, and methods. There is an excellent, albeit brief, discussion of Bessel, Chebyshev, Butterworth and other filter types. The following three chapters cover specific LP, BP and HP filter circuits. Sallen-Key and state-variable filters are among those included. As in the previous chapters, there are the helpful math-background and design-example sections. There are also design-guide block schematics with instructive call-outs.

The final two chapters are on tuning, voltage control, special types and applications. There is a short list of reference articles and texts. The six-page index is quite good, but there are some omissions. Overall, Lancaster's book is very well organized and presented with numerous helpful figures.

It should be of value to those who would learn and do.

-Howard A. Roberson

(adapted from Audio magazine, Feb. 1979)

Also see: Bookshelf, The (Sept. 1987)

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