Architectural Acoustics (eBook)

Marshall Long (Autor)

eBook Download: PDF | EPUB

2014 | 2. Auflage
984 Seiten
Elsevier Science (Verlag)
978-0-12-398265-0 (ISBN)

Infos

Architectural Acoustics, Second Edition presents a thorough technical overview of the discipline, from basic concepts to specific design advice. Beginning with a brief history, it reviews the fundamentals of acoustics, human perception and reaction to sound, acoustic noise measurements, noise metrics, and environmental noise characterization. In-depth treatment is given to the theoretical principles and practical applications of wave acoustics, sound transmission, vibration and vibration isolation, and noise transmission in floors and mechanical systems. Chapters on specific design problems demonstrate how to apply the theory, including treatment of multifamily dwellings, office buildings, rooms for speech, rooms for music, multipurpose rooms, auditoriums, sanctuaries, studios, listening rooms, and the design of sound reinforcement systems. Detailed figures illustrate the practical applications of acoustic principles, showing how to implement design ideas in actual structures. This compendium of theoretical and practical design information brings the relevant concepts, equations, techniques, and specific design problems together in one place, including both fundamentals and more advanced material. Practicing engineers will find it an invaluable reference for their daily work, while advanced students will appreciate its rigorous treatment of the basic building blocks of acoustical theory. - Considered the most complete resource in the field - includes basic fundamental relations, derived from first principles, and examples needed to solve real engineering problems. - Provides a well-organized text for students first approaching the subject as well as a reliable reference for experienced practitioners looking to refresh their technical knowledge base. - New content for developing professionals includes case studies and coverage of specific focus areas such as audio visual design, theaters, and concert halls.

Since 1971, Marshall Long has been engaged in acoustical engineering consulting as principal of the firm he founded. Based in California, USA, Marshall Long Acoustics, has established a national and international reputation, completing over 3,000 projects in architectural acoustics, noise and vibration control, environmental impact assessment, and audio visual design. With engineering degrees from Princeton and UCLA, Dr. Long has taught acoustical engineering courses at UCLA and Southern California Institute of Architecture, and has guest lectured at Cal State Long Beach and USC. He has published numerous papers and articles in the field of acoustics. The author has recently been awarded a US patent on the recording and reproduction of three-dimensional sound. For further information visit the firm's website at mlacoustics.com.

Textauszug

1

Historical Introduction

Abstract

Chapter 1 begins with a historical review of the relationship between architecture and the acoustics of spaces. It includes a discussion of the progress of building construction along with its influence on music and discourse. The chapter begins with the early cultures including the Greek and Roman theaters and continues into the twentieth century with the development of the science of acoustics and the mathematical modeling of sound in rooms. The chapter discusses important cultures throughout the intervening ages, including the Renaissance and Baroque periods, and highlights influencial figures such as Wallace Clement Sabine.

Keywords

historyacousticstheaterchurchcathedralopera houseshoebox hallconcert hallSabinesound theory

The arts of music, drama, and public discourse have both influenced and been influenced by the acoustics and architecture of their presentation environments. It is theorized that African music and dance evolved a highly complex rhythmic character, rather than the melodic line of early European music due, in part, to its being performed outdoors. Wallace Clement Sabine (1868–1919), an early pioneer in architectural acoustics, felt that the development of a tonal scale in Europe rather than in Africa could be ascribed to the differences in living environment. In Europe, prehistoric tribes sought shelter in caves and later constructed increasingly large and reverberant temples and churches. Gregorian chant grew out of the acoustical characteristics of the Gothic cathedrals, and subsequently baroque music was written to accommodate the churches of the time. In the latter half of the twentieth century both theater design and performing arts became technology-driven, particularly with the invention of the electronic systems that made the recording, film, and television industries possible. With the development of computer programs capable of creating the look and sound of any environment, a work of art can now not only influence, but also define the space it occupies.

Greek and Roman Period (650 BC–AD 400)

Early Cultures

The origin of music, beginning with some primeval song around an ancient campfire, is impossible to date. There is evidence (Sandars, 1968) to suggest that instruments existed as early as 13,000 BC. The understanding of music and consonance dates back at least to 3000 BC, when the Chinese philosopher Fohi wrote two monographs on the subject (Skudrzyk, 1954).

The earliest meeting places were probably no more than conveniently situated open areas. Their form was whatever existed in nature and their suitability to purpose was haphazard. As the need arose to address large groups for entertainment, military, or political purposes, it became apparent that concentric circles brought the greatest number of people close to the central area. Since the human voice is directional and intelligibility decreases as the listener moves off axis, seating arrangements were defined by the vocal polar pattern and developed naturally, as people sought locations yielding the best audibility. This led to the construction of earthen or stone steps, arranging the audience into a semicircle in front of the speaker. The need to improve circulation and permanence evolved in time to the construction of dedicated amphitheaters on hillsides based on the same vocal patterns.

Greeks

The Greeks, perhaps due to their democratic form of government, built some of the earliest outdoor amphitheaters. The seating plan was in the shape of a segment of a circle, slightly more than 180°, often on the side of a hill facing the sea. One of the best-preserved examples of Greco-Hellenistic theaters is that built at Epidaurus in the northeastern Peloponnese in 330 BC, about the time of Aristotle. A sketch of the plan is shown in Fig. 1.1. The seating was steeply sloped in these structures, typically 2:1, which afforded good sight lines and reduced grazing attenuation. Even with these techniques, it is remarkable that this theater, which seated as many as 17,000 people, actually functioned.

Figure 1.1Ancient Theater, Epidaurus, Greece (Izenour, 1977)

The ancient Greeks were aware of other acoustical principles, at least empirically. Chariot wheels in Asia Minor were heavy, whereas those of the Greeks were light since they had to operate on rocky ground. To achieve high speed, the older Asian design was modified, so that the four-spoke wheels were smaller and the wooden rims were highly stressed and made to be very flexible. They were so light that if left overnight under the weight of the chariot they would undergo deformation due to creep. Telemachus, in Homer’s story of the Odyssey, tipped his vehicle vertically against a wall, while others removed their wheels in the evening (Gordon, 1978) to prevent warping. The wheels were mounted on light cantilevered shafts and the vehicle itself was very flexible, to help isolate the rider from ground-induced vibrations.

Greek music and dance were highly developed arts. In 250 BC at a festival to Apollo, a band of several hundred musicians played a five-movement piece celebrating Apollo’s victory over Python (Rolland et al., 1948). There is strong evidence that the actors wore masks that were fitted out with small megaphones to assist in increasing the directivity of the voices. It is not surprising that the Greek orator Demosthenes (c. 384–322 BC) was reputed to have practiced his diction and volume along the seashore by placing pebbles in his mouth. Intelligibility was enhanced, not only by the steeply raked seating, but also by the naturally low background noise of a preindustrial society.

The chorus in Greek plays served both as a musical ensemble, as we use the term today, and as a group to chant the spoken word. They told the story and explained the action, particularly in the earlier plays by Aeschylus (Izenour, 1977). They may have had a practical as well as a dramatic purpose, which was to increase the loudness of the spoken word through the use of multiple voices.

Our knowledge of the science of acoustics also dates from the Greeks. Although there was a general use of geometry and other branches of mathematics during the second and third millennia BC, there was no attempt to deduce these rules from first principles in a rigorous way (Dimarogonas, 1990). The origination of the scientific method of inquiry seems to have begun with the Ionian School of natural philosophy, whose leader was Thales of Miletus (624–546 BC), the first of the seven wise men of antiquity. While he is better known for his discovery of the electrical properties of amber (electron in Greek), he also introduced the logical proof for abstract propositions (Hunt, 1978) that led in time to the formal mathematics of geometry, based on the theorem-proof methods of Euclid (330–270 BC).

Pythagoras of Samos (c. 570–497 BC), a contemporary of Buddha, Confucius, and Lao-Tse, can be considered a student of the Ionian School. He traveled to Babylon, Egypt, and probably India before establishing his own school at Crotone in southern Italy. Pythagoras is best known for the theorem that bears his name, although it was discovered much earlier in Mesopotamia. He and his followers made important contributions to number theory and to the theory of music and harmony. The word theorii appeared in the time of Pythagoras meaning “the beauty of knowledge” (Herodotus, c. 484–425 BC). Boethius (AD 480–524), a Roman scholar writing a thousand years later, reports that Pythagoras discovered the relationship between the weights of hammers and the consonance of their natural frequencies of vibration. He is also reported to have experimented with the relationship between consonance and the natural frequencies of vibration of stretched strings, pipes, shells, and filled vessels. The Pythagorean School started the scientific exploration of harmony and acoustics through these studies. They understood the mechanisms of generation, propagation, and perception of sound (Dimarogonas, 1990). Boethius describes their knowledge of sound in terms of waves generated by a stone falling into a pool of water. They probably realized that sound was a wave propagating through the air and may have had a notion of the compressibility of air during sound propagation.

Aristotle (384–322 BC) recognized the need for a conducting medium and stated that the means of propagation depended on the properties of the material. There was some confusion concerning the relationship between sound velocity and frequency, clarified by Theophrastus of Eresos (371–287 BC): “The high note does not differ in speed, for if it did it would reach the hearing sooner, and there would be no concord. If there is concord, both notes must have the same speed.” The first monograph on the subject, On Acoustics, is attributed to Aristotle, although it may have been written by his followers. Whoever wrote it, the author had a clear understanding of the relationship between vibration and sound: “bodies that are capable of vibrating produce sounds … strings are examples of such bodies.”

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Produkt-Details

• Erscheint lt. Verlag: 5.2.2014
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Mechanik
• Themenwelt: Technik ► Architektur
• ISBN-10: 0-12-398265-0 / 0123982650
• ISBN-13: 978-0-12-398265-0 / 9780123982650