Sound Absorption And Sound Power Measurements In Reverberation Chambers Using Energy Density Methods PDF Download
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Author | : David B. Nutter |
Publisher | : |
Total Pages | : 115 |
Release | : 2006 |
Genre | : Absorption of sound |
ISBN | : |
Download Sound Absorption and Sound Power Measurements in Reverberation Chambers Using Energy Density Methods Book in PDF, ePub and Kindle
Measurements in a reverberation chamber use spatially averaged squared pressure to calculate sound absorption, sound power, and other sound measurements. While a reverberation chamber provides an approximation of a diffuse sound field, variations in the measurements introduce uncertainty in measurement results. Room qualification procedures require a sufficient number of source-receiver locations to obtain suitable measurements. The total acoustic energy density provides greater spatial uniformity than squared pressure, which requires fewer source-receiver positions to produce similar or better accuracy in measurement results. This paper explores the possibility of using energy density in place of squared pressure, using methods outlined in current ISO standards, by describing several experimental and analytical results.
Author | : Travis Nathan Hoyt |
Publisher | : |
Total Pages | : 99 |
Release | : 2019 |
Genre | : Electronic dissertations |
ISBN | : |
Download Improvements to Sound Power Measurements for Large, Extended Sources in Semi-reverberant Rooms Using Generalized Energy Density Book in PDF, ePub and Kindle
Sound power measurements of acoustic sources are typically performed in anechoic or reverberation chambers using acoustic pressure according to international standards. The anechoic chamber creates a free-field environment where the sound power is estimated from the squared pressure integrated over some enveloping surface. The reverberation chamber produces diffuse-field conditions, where sound power is proportional to the spatially averaged squared pressure. In semi-reverberant environments, the direct and reverberant energies each contribute to the total measured field. If the kinetic and potential components of acoustic energy density are weighted appropriately, the spatial variation of the field can be significantly reduced compared to squared pressure. This generalized energy density allows an adaptation of the sound power formulation by Hopkins and Stryker to be used to make an efficient and accurate in situ sound power estimate of a noise source in a non-ideal acoustical environment. Since generalized energy density optimizes the spatial uniformity of the field, fewer measurement positions are needed compared to traditional standards. However, this method breaks down for sources that are large and extended in nature and considerably underestimates the sound power. This thesis explores the practical limits of this method related to the sound power underestimation. It also seeks to understand the special considerations necessary to achieve accurate, survey-grade sound power data of large, extended noise sources through a laboratory study of custom extended and compact sources. A modified method to accurately and efficiently measure the sound power of large, extended sources is proposed with results.
Author | : Daniel R. Marquez |
Publisher | : |
Total Pages | : 265 |
Release | : 2014 |
Genre | : Electronic dissertations |
ISBN | : |
Download Estimating the Acoustic Power of Sources in Nonideal Enclosures Using Generalized Acoustic Energy Density Book in PDF, ePub and Kindle
Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This paper introduces two measurement methods that utilize a weighted combination of potential and kinetic energy densities, known as generalized acoustic energy density, to estimate sound power in nonideal semi-reverberant rooms. The first method employs a generalized sound power formulation, which is an adaptation to an equation developed in 1948 for semi-reverberant spaces. The second, called the two-point in situ method, is a technique based on the generalized sound power formulation for quick and accurate in situ sound power estimates. Since the generalized acoustic energy density is more spatially uniform than the squared acoustic pressure in an enclosed field, these methods have the advantage of achieving the same accuracy in sound power determination with fewer measurement positions. This thesis explores the possibility of using these new methods in place of methods outlined in current ISO standards by describing analytical, numerical, and experimental results.
Author | : D. Lubman & Associates |
Publisher | : |
Total Pages | : 28 |
Release | : 1974 |
Genre | : Acoustical engineering |
ISBN | : |
Download Review of Reverberant Sound Power Measurement Standard and Recommendations for Further Research Book in PDF, ePub and Kindle
Author | : Tina Marie Famighetti |
Publisher | : |
Total Pages | : |
Release | : 2005 |
Genre | : Acoustical engineering |
ISBN | : |
Download Investigations Into the Performance of the Reverberation Chamber of the Integrated Acoustics Laboratory Book in PDF, ePub and Kindle
This thesis details the performance of the reverberation chamber of the Integrated Acoustics Laboratory (IAL), equipped with experimental lightweight diffusers. Reverberation chambers are generally equipped with dense baffles, called diffusers, which are designed to reflect but not absorb sound, in an effort to create a sound field in the chamber with uniform energy density. Industry standards, such as ASTM C423, ISO 354, and ISO 3741 for sound absorption and sound power testing in reverberation chambers, recommend the use of stationary and rotating diffusers, made of a material with high surface density and low absorption. Instead, lightweight fiberglass diffuser panels were installed in the IAL reverberation chamber because they are safer, less expensive and more flexible; their performance in the IAL chamber was evaluated. Preliminary testing of the IAL instrumentation chain and analysis techniques documented their acceptable performance. Qualification testing per the abovementioned standards proved that the IAL chamber, equipped with stationary lightweight diffusers, was fit for testing sound power but not sound absorption. However, when equipped with a combination of stationary and rotating lightweight diffusers, the chamber qualified for sound absorption tests. Optimization of absorption testing methodology showed that specimen area did not significantly affect the measured sound absorption coefficient unless the specimen was highly absorptive or the area was significantly less than the recommended 6.69 m2. Also, increasing the?empty room? absorption of the acoustically hard IAL chamber did not improve the reproducibility of absorption measurements. With regard to length of test, absorption tests in the IAL chamber should include the measurement of 225 decays to attain the representative repeatability values of ASTM C423 for frequencies 315 Hz and higher. Comparative absorption testing showed that the chamber reproduced sound absorption results well; when round robin testing was replicated in the chamber, results were not statistically different from other laboratories. However, the reproducibility was worse for highly absorptive specimens. Sound power testing produced highly reproducible results, well within the limits of reproducibility of the standard. It can be concluded that a combination of stationary and rotating lightweight diffusers made the IAL chamber fit for sound absorption and sound power testing.
Author | : Jiri Tichy |
Publisher | : |
Total Pages | : 244 |
Release | : 1975 |
Genre | : |
ISBN | : |
Download Sound Power Measurements in Reverberation Chambers Book in PDF, ePub and Kindle
Author | : Sherman F. Booth |
Publisher | : |
Total Pages | : 974 |
Release | : 1961 |
Genre | : Industrial safety |
ISBN | : |
Download National Bureau of Standards Handbook Book in PDF, ePub and Kindle
Author | : United States. National Bureau of Standards |
Publisher | : |
Total Pages | : 1004 |
Release | : 1961 |
Genre | : Industrial safety |
ISBN | : |
Download National Bureau of Standards Handbook Book in PDF, ePub and Kindle
Author | : M. P. Norton |
Publisher | : Cambridge University Press |
Total Pages | : 644 |
Release | : 2003-10-16 |
Genre | : Science |
ISBN | : 9780521499132 |
Download Fundamentals of Noise and Vibration Analysis for Engineers Book in PDF, ePub and Kindle
Noise and Vibration affects all kinds of engineering structures, and is fast becoming an integral part of engineering courses at universities and colleges around the world. In this second edition, Michael Norton's classic text has been extensively updated to take into account recent developments in the field. Much of the new material has been provided by Denis Karczub, who joins Michael as second author for this edition. This book treats both noise and vibration in a single volume, with particular emphasis on wave-mode duality and interactions between sound waves and solid structures. There are numerous case studies, test cases, and examples for students to work through. The book is primarily intended as a textbook for senior level undergraduate and graduate courses, but is also a valuable reference for researchers and professionals looking to gain an overview of the field.
Author | : |
Publisher | : |
Total Pages | : 200 |
Release | : 1973 |
Genre | : Industrial safety |
ISBN | : |
Download NBS Handbook Book in PDF, ePub and Kindle