11-12-2012, 04:51 PM
A SEMINAR REPORT ON ACOUSTIC DESIGN AND MATERIALS
ACOUSTIC DESIGN.doc (Size: 6.78 MB / Downloads: 346)
Abstract
The present scenario of living is different from the earlier ages in many sorts of features for e.g. expedited technological growth has caused us to live between machines, their operations and in an environment synchronized with their relationships with us. The rising use of automation and fabricated methodologies has impacted us in a variety of ways. The result being less pleasant environments in terms of polluted resources, increased exposure to toxins and not to mention the ever growing increased auditory of sound.While our forefathers lived in relative tranquility, we are subjected to an incredible increase in the sources of noise and noise intensity both inside & outside our buildings, often with serious and harmful effects. This over exposure to sound has forced to devise techniques and methodologies in order to control and mitigate over hearing conditions. Hence “Acoustics” can be defined as a science of sound, which deals with origin, propagation and auditory sensation of sound, and also with design & construction of different building units to set optimum conditions for producing &listening speech, music, etc. the study of acoustics is a very necessary discipline these days as it employs designing interiors of auditoriums, theatres, and other structures to enhance their audacity features. The study of acoustics dates back to Pythagoras who studied vibrating strings and musical sounds. He apparently discovered that dividing the length of a vibrating string into simple ratios produced consonant musical intervals. The Roman architect Vitruvius was the first to write about it in his monumental De Architectura, which includes a remarkable understanding and analysis of theater acoustics. Galileo reviewed the relationship of the pitch of a string to its vibrating length, and he related the number of vibrations per unit time to pitch. In the 19th century much of the progress in acoustical studies was done by eminent scientists and sound engineers like Alexander Graham Bell, Rudolph Koenig, Rayleigh, George Stokes, Tyndall etc. In 1867 Tyndall published his book On Sound which laid a great deal of light upon the transmission of sound through the atmosphere and on combinations of musical tones. In this very century a new field of “architectural acoustics” started to emerge and much of its development is credited to Wallace Clement Sabine (1868–1919) who is also generally considered to be the father of architectural acoustics. He was the first to make quantitative measurements on the acoustics of rooms. His discovery that the product of total absorption and the duration of residual sound is a constant still forms the basis of sound control in rooms.
Introduction
ACOUSTICS: general definition
"Acoustics" is a science of sound, which deals with origin, propagation and auditory sensation of sound, and also with design & construction of different building units to set optimum conditions for producing &listening speech, music, etc. The word "acoustic" itself is derived from the Greek word ακουστικός (akoustikos), meaning "of or for hearing, ready to hear" and that from ἀκουστός (akoustos), "heard, audible", which in turn derives from the verb ἀκούω (akouo), "I hear". In other words “acoustics” is defined as the branch of science and engineering in which we study the characteristics and principles of sound propagation and its interaction with matter, to design and create structures having optimum hearing conditions. Acoustics has become a very complex and interdisciplined science these days and it wouldn’t be wrong if we say that it encompasses the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and others. The science has many sub divisions also, namely architectural acoustics, physical acoustics, musical acoustics, psychoacoustics, electroacoustic, noise control, shock and vibration, underwater acoustics, speech, physiological acoustics, etc. while the architectural acoustics deals with the design of soundproofed interiors of buildings and establishments, other branches like underwater acoustics have applications like SONAR( sound detection and ranging) . Through the use of architectural acoustics and its principles better and more soundproofed interiors of buildings and establishments like auditoriums, movie theatres, concert halls are being designed.
Architectural Acoustics:
Architectural acoustics is the branch of acoustics in which we study the designing and construction of buildings having soundproofed interiors. The acoustical design issues for buildings involve the principal issues like site noise considerations, including the control of noise transfer to a project’s neighbors, particularly if they are residential, establishing noise standards for each use space, including limitation of excessive ventilation noise, room acoustics considerations, sound isolation between various use spaces, vibration control for mechanical equipment, audio/visual system considerations.
History of Architectural Acoustics:
Acoustics is the science of sound. Although sound waves are nearly as old as the universe, the scientific study of sound is generally considered to have its origin in ancient Greece. The word acoustics is derived from the Greek word akouein, to hear, although Sauveur appears to have been the first person to apply the term acoustics to the science of sound in 1701. Pythagoras, who established mathematics in Greek culture during the sixth century BC, studied vibrating strings and musical sounds. He apparently discovered that dividing the length of a vibrating string into simple ratios produced consonant musical intervals. Besides the Greeks, the Roman architect Vitruvius was the first to write about it in his monumental De Architectura, which includes a remarkable understanding and analysis of theater acoustics: “We must choose a site in which the voice may fall smoothly, and not be returned by reflection so as to convey an indistinct meaning to the ear.” The historical development of architectural acoustics is similar to other fields of building design, in comprising two parallel strands of ideas – the science and mathematics of the subject on the one hand, leading to improved understanding of the phenomena, and the methods used by designers when faced with the challenge of a new building on the other, especially when the task differs markedly from precedent. The two nineteenth- century classic works on the physics of acoustics (Helmholz 1863; Strutt 1877-78) hardly mentioned the acoustics of theatres or other rooms, and the science they contained only began to be used by architectural acousticians in the mid-twentieth century. While these two branches of knowledge are closely related, it was not a case of theory leading to practice, or vice versa: the two were symbiotic.
• RENAISSANCE PERIOD (1400–1600):
Church construction still continued to flourish in the early years of the Renaissance. St. Peter’s Cathedral in Rome, the most important building of the period, was begun in 1506 and was created by many of the finest architects and artists of the day. Theater construction began again in Italy in the early Renaissance, more or less where the Romans had left it a thousand years earlier. In 1580, the Olympic Academy in Vicenza engaged Palladio (1518–1580) to build a permanent theater , the first since the Roman Odeons. The seating plan was semi-elliptical, following the classical pattern, and the stage had much the same orchestra and proskenium configuration that the old Roman theaters had. In 1588, Scamozzi further modified the Roman plan in a new theater, the Sabbioneta, The semi-elliptical seating plan was pushed back into a U shape, the stage wall was removed, and a single-point perspective backdrop replaced the earlier multiple-point perspectives. Its seating capacity was small and there was little acoustical support from reflections off the beamed ceiling.