Handbook for Sound Engineers

Glen Ballou, Glen Ballou

• Publisher: Routledge
• Year: 2015
• ISBN:
  9781135016654
• Edition: 5
• Topic: Tecnología e ingeniería
• Subtopic: Ingeniería acústica

Handbook for Sound Engineers is the most comprehensive reference available for audio engineers, and is a must read for all who work in audio.

With contributions from many of the top professionals in the field, including Glen Ballou on interpretation systems, intercoms, assistive listening, and fundamentals and units of measurement, David Miles Huber on MIDI, Bill Whitlock on audio transformers and preamplifiers, Steve Dove on consoles, DAWs, and computers, Pat Brown on fundamentals, gain structures, and test and measurement, Ray Rayburn on virtual systems, digital interfacing, and preamplifiers, Ken Pohlmann on compact discs, and Dr. Wolfgang Ahnert on computer-aided sound system design and room-acoustical fundamentals for auditoriums and concert halls, the Handbook for Sound Engineers is a must for serious audio and acoustic engineers.

The fifth edition has been updated to reflect changes in the industry, including added emphasis on increasingly prevalent technologies such as software-based recording systems, digital recording using MP3, WAV files, and mobile devices. New chapters, such as Ken Pohlmann's Subjective Methods for Evaluating Sound Quality, S. Benjamin Kanters's Hearing Physiology—Disorders—Conservation, Steve Barbar's Surround Sound for Cinema, Doug Jones's Worship Styles in the Christian Church, sit aside completely revamped staples like Ron Baker and Jack Wrightson's Stadiums and Outdoor Venues, Pat Brown's Sound System Design, Bob Cordell's Amplifier Design, Hardy Martin's Voice Evacuation/Mass Notification Systems, and Tom Danley and Doug Jones's Loudspeakers. This edition has been honed to bring you the most up-to-date information in the many aspects of audio engineering.

Part 1

Introduction to Sound and Acoustics

Chapter 1

Audio and Acoustic DNA—Past and Present

by Don and Carolyn Davis

1.1 Introduction

1.2 Gestalt Theory

1.3 Music in Acoustics

1.4 Sales or Communication?

1.5 Motional Impedance

1.6 Genesis

1.7 1893—The Magic Year

1.8 Bell Laboratories and Western Electric

1.8.1 Negative Feedback—1927

1.8.2 The dB, dBm and the VI

1.8.3 Bell Labs and Talking Motion Pictures

1.8.4 Motion Pictures—Visual versus Auditory

1.8.5 The Transition from Western Electric to Private Companies

1.9 LEDE Studio

1.10 Audio Publications

1.11 The “High” Fidelity Equipment Designers

1.12 Sound System Equalization

1.13 Real-time analysis RTA

1.14 Altec Classes

1.15 JBL

1.16 Acoustics

1.17 Professional-Level Audio Equipment Scaled to Home Use

1.17.1 The Invention of Radio and Fidelity

1.18 Acoustic Measurements

1.19 Calculators and Computers

1.20 Other Giants in Our Lives

1.21 Sound System Engineering

Bibliography

1.1 Introduction

This chapter is the DNA of my ancestors, the giants who inspired and influenced our lives. If you or a hundred other people wrote this chapter, your ancestors would be different. We hope you find reading the DNA of our ancestors worthwhile and that it will provoke you into learning more about them.

Interes t in my audio and acoustic ancestors came about by Carolyn and I starting the first independent Hi-Fi shop, The Golden Ear, in Lafayette, Indiana in early 1952. The audio enthusiasts from Purdue came to our shop to meet the great men of hi-fi; Paul Klipsch, Frank McIntosh, Gordon Gow, H.H. Scott, Saul Marantz, Rudy Bozak, Avery Fisher—manufacturers who exhibited in the Hi-Fi shows at the Hollywood Roosevelt and the Hilton in New York City. We sold our shops in Indianapolis and Lafayette in 1955, and took an extended trip to Europe. In 1958 I went to work for Paul Klipsch as his “President in Charge of Vice.” Mr. Klipsch introduced me to the writings of Lord Kelvin, the Bell Labs West Street personnel, as well as to his untrammeled genius.

Don and Carolyn Davis and “The Golden Ear”

Altec was the next stop, with my immediate manager being “the man who made the motion picture talk.” At Altec I rubbed against and was rubbed against by the greats and those who knew the Greats and those who knew the Greats from the inception of the Art. This resulted in our awareness of the rich sense of history we have been a part of and we hope that sharing our remembrance will help you become alert to the richness of your own present era.

In 1972 Carolyn and I were privileged to work with the leaders in our industry who came forward to support the first independent attempt at audio education, Synergetic Audio Concepts (SynAudCon). These manufacturers represented the best of their era and they shared freely with us and our students without ever trying to “put strings on us.”

Thoughts for Today. I want to discuss many of my contemporaries in this new section because in conversations with newcomers to the field I have shared several of those stories with them and they have found them inspiring. Each of these individuals led my thinking in a new direction and often, as indicated, were a direct assistance to the task at hand. They all possessed traits of character, that made them valuable members of society. Carolyn and I have always sought alertness to talented individuals in any field. They are fun to know, a challenge to keep up with, and a guide to a fuller understanding of viewpoints not formerly considered.

Few of us ever chose audio and acoustics as a career but rather those subjects chose us as we were led by our innate experiences (love of music, ham radio, etc.) into appreciation of the how, what, and why of the technology behind the toys that gave us pleasure in our early lives.

1.2 Gestalt Theory

While men and women attracted to acoustics are often listeners to classical music and appreciators of visual art, their counterparts in audio are often more fastened on the scientific aspects of the material components used in their work.

Ernst Mach wrote, We do not perceive the world in itself, if we did we would perceive chaos. Thus we have evolved senses that perceive contrasts of perception, relations of perception. Sensations by themselves can have no organic meaning; only the relations of sensations to one another can have meaning.

Perception, Mach believed, is never perception of direct stimuli. Sensations are not simply raw experiences, but the interaction of experience with a preformed cognitive structure. For instance, when we hear a known melody, we recognize it no matter what key it is played in. It can be hummed, buzzed, or strummed on a guitar. Furthermore, even if one or more notes are incorrect, we still recognize it.

Ernst Mack

Mach asks, What constitutes a melody? It seems incorrect to say that the actual sound vibrations constitute the melody as we have just seen that numerous different sounds can make the same melody. But on the other hand, it seems empirically odd to say that a melody is not constituted out of its sounds. The actual melody, then, exists in our ability to recognize it. It is formed by experience of one or more examples of the melody, but it is an idealization of that experience. Significantly, the idealization captures not the actual sounds, but the relationships of the sounds to one another. For Mach, this process is at the basis of all perception.

Experience requires an “a priori,” but that “a priori” is itself formed by experience. Men and women who have, through experience, learned the deceptive nature of the five physical senses, learn more readily the nuances of acoustic measurements as well as the optimum number and placement of microphones in recording situations. It is the inept in recording work that resorts to close miking and asks “where shall I place the microphone” for a measurement.

They have ears that receive signals but the “listening capability” between them is relatively unprogrammed. There is a great deal of evidence that the current generation in audio have been exposed to highly undesirable “a priori” both in program material and cultural background.

In all professional work one should seek out the real standards that apply which are not necessarily those that are currently in use by the majority. To measure anything meaningfully requires:

1. Experience with similar devices.

2. Mathematical analysis of the device and its most likely performance.

3. Cut and try experimentation.

Obviously the mathematical approach is often the quickest. Experience with similar devices occurs when someone knowledgeable guides you through a process they are already very familiar with. Cut-and-try can overtime, hopefully with a minimum amount of destruction, lead to experience. In the long run, all measurement runs up against a trained listener’s perception. Yes! I know any untrained listener can be satisfied with trash, but any professional’s goal should be acceptance by the trained listener. When that occurs you have gained membership in a privileged peer group.

Ernst Mach 1838–1916, a contemporary of Gustav Fechner the psycho-acoustician, was acknowledged by Einstein as being the philosophical forerunner of relativity. Early in his life Mach defended Christian Doppler against two prominent physicists, Petzval and Angstrom who had challenged the “Doppler effect” by building an apparatus that consisted of a six foot tube with a whistle at one end that rotated in a vertical plane. When the listener stood in the plane of the axis of rotation no changes in pitch could be heard. But if the observer stood in the plane of rotation, fluctuations in pitch that corresponded to the speed of rotation could be heard.

Mach discovered that the eye has a mind of its own; we perceive not direct stimuli but relations of stimuli. The visual system operates through a process of continual adaptation of the present sensation to previous ones. We do not experience reality but rather experience the after effects of our nervous systems adaptations to new stimuli. Our cognitive structure is itself formed through previous experience, and our current experience is structured by it in turn. Mach claimed “We do not perceive the world in itself, if we did we would perceive chaos.” From Gustav Fechner’s work.

1.3 Music in Acoustics

The following is from Frederick V. Hunt, The Origin of Acoustics.

The broad implications of what Sarton called “The cause and cure of Scholasticism” may seem to be strange grist for the acoustic mill. There were at least two reasons, however, why the branch of acoustics dealing with music was able to make a unique contribution toward the ultimate conquest of scholasticism. The first was that music was insured a firm continuing hold on its place in the scholastic sun by virtue of its role as a part of the classical quadrivium (Astronomy, Geometry, Mathematics, Music.) Educators, philosophers, encyclopedist, and commentators alike had pre-force to deal with music and with the evolution of musical science. The second basis for the close relation between music and scholasticism stemmed from the fact that music is, sui generis, an epitome of experimental science. Objective in execution and humanistic in appreciation, its three aspects of composition, performance, and appreciation exemplified—and held up continuously for conscious or unconscious regard—the scientific credo of hypothesis, experiment, and conclusion.

Almost every medieval writer who considered the theory of music felt obliged to devote at least one section of his treatise to the production of sound and to the factors that influence pitch. Since the Greeks had already achieved an un...