Measurementsin Building Acoustics (original) (raw)
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Reflectance Profile Method for the Acoustical Design of Buildings
The acoustic character of interior enclosed spaces is typically described by Reverberation Time (RT-60) and presented as a single value based on the Noise Reduction Coefficient for the total number of sabins in a spatial volume. When a series of reverberation times are calculated at frequency band centers, well-accepted terminology can be applied for describing the space for conditions where reverberation is missing, prevalent, or excessive. Therefore, reverberation time provides a spatial description but little about the material properties of room surfaces that create the condition. This paper presents a simple methodology for calculating the Reflectance Profile of a space. Examples of typical spaces such as hotel rooms and elementary school classrooms are included to demonstrate its utility as a design tool. The Glass House, a proposed music hall entirely enclosed in glass, is also included to indicate how the Reflectance Profile can provide an easy, understandable means of identifying corrective measures that should be employed during design to avoid frequency imbalance. It has led to the study of triangular non-damping reflective glass panels for use in the Glass House. 1 INTRODUCTION Reverberation time provides a means for presenting a single number value to describe the natural decay of sound introduced into an enclosed space. The equation for reverberation time (RT60) is extremely simple. Reverberation time is proportional to the cubic volume of the space divided by the sum of the surface areas of various materials times their sound absorption rates with a constant related to the amount of decay in decibels. For SI units and 60 dB of decay: T = 0.16 V/S In presenting the reverberation time any information about the actual makeup of the materials used to absorb the sound is lost. As a result it is difficult to see how to easily modify these combined values to improve conditions in the room. Sounds heard in a space have been changed by the surfaces of materials comprising the enclosure by reflecting various frequencies in different amounts to contribute to the reverberant qualities. It is fair to say that architects are more interested in the reflections of the sounds than the loss of reflections through absorption since the reflections are what are heard. This is true even
19th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007
ABSTRACT Room acoustics can be modeled by simulating the propagation of acoustic energy in the space under consideration. Thus, it is possible to formulate a room acoustic rendering equation which perfectly describes the time-dependent distribution of the energy. The current room acoustics modeling methods can be derived as special cases of this equation. In addition, an acoustic radiance transfer method has been constructed for modeling the sound propagation in environments with arbitrary reflection properties.
2010
The article reviews modern techniques for analyzing room response of small spaces for listening, recording and rehearsing music both in the time and the frequency domain. After a brief review of theories and norms it discusses the techniques using actual measurement results as examples. This allows to show typical non-Sabinian behaviors of small rooms with short time decays (Volume < 100 m3, T30 < 0.5 sec). The study of single reflections, modal perduration in time and frequency distribution allows to point out and verify the phenomena that can be controlled by the acoustic designer through surface treatment, source-receiver positioning and room shape modification.
ARCHITECTURAL ACOUSTICS BASIC ASPECTS OF ARCHITECTURAL ACOUSTICS
SUMMARY In all the buildings there are noises and must also consider the vibrations that are transmitted by the walls and structure. The traditional way of avoiding the transmission of vibrations is not only with large masses, we can achieve this by means of lightweight panels. This work of ideas to achieve it. Control of noise in buildings, isolation of noise and vibrations from the structure and activities of the people who live there. In general the insulation of the walls and the slabs of mezzanine with the adjacent spaces. For example, block walls 20 cm thick have a transmission loss averaging 50 dB, while two walls 10 cm thick with a 10 cm air chamber will have almost 60 dB of transmission loss which represents a thickness of 30 cm and in many cases of design cannot have such solution. The calculation of the loss of sound transmission began in 1940 by Cremer, and by various scientists including R. Josse and C. Lamure in 1949 and more recently H. Arau in 1982 being the most accepted by Josse and Lamure, from where Is considered the mass of the surface and its resistance to vibration. The calculations based on the weight of the surface, the sound energy was harder to put vibrating a surface with little weight, I explain if they have a table and move it with your hands will vibrate easily, now place book and other objects on the same table and try again to make it move, it will cost more energy to achieve it, if more weight more energy. Sound is an energy that moves and when it hits a surface it will vibrate and sometimes it vibrates and it persists in time these vibrations can collapse the structure, remember the soprano that with its voice towards explodes a glass or the sergeant which orders the troop to break the pass through when approaching the bridge and to the Tacoma Bridge Narrows was a suspension bridge of 1600 meters in length with a distance between supports of 850 m (the third largest in the world at the time it was built) Is the