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Proceedings of Meetings on Acoustics

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POMA - 159th Meeting  Acoustical Society of America/NOISE-CON 2010
Conference Location: Baltimore, Maryland Conference Date: 19 - 23 April 2010
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New York City: The (E) Designation and Restrictive Declaration

Benjamin Sachwald

POMA Volume 9, pp. 040001 (April 2010); (7 pages)

Online Publication Date: April 08, 2010

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Urban areas are typically associated with high noise levels. With a population of more than eight million and growing, New York City is one of the largest cities in the world. In New York City, because of the population density and the wide variety of land uses (ex: residential, commercial, transportation, manufacturing and industrial) that exist in close proximity, it is common for a residential building to be located in an area with ambient noise levels that would be considered unsuitable for residential use. To protect inhabitants of a planned building to be located in an area with high ambient noise levels, an (E) designation or a Restrictive Declaration may be used to ensure that the building's interior environment meets a certain acoustical design criterion. In this paper, the (E) designation is defined, its regulatory process is outlined, the acoustical design criterion is discussed, and examples of common mistakes for noise (E) designation projects are listed.
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43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.55.Rg Sound transmission through walls and through ducts: theory and measurement
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Survey of Ambient Noise in Aquariums

Colin Jemmott

POMA Volume 9, pp. 040002 (April 2010); (9 pages)

Online Publication Date: April 16, 2010

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Owning and maintaining an aquarium is a common hobby, but some aspects of proper animal husbandry in the hobby community have received little scientific attention. Specifically, the ambient noise in aquariums resulting from pumps, filters, bubblers and other equipment is not well studied, yet elevated ambient noise levels have been shown to adversely affect fish and marine invertebrates. Anecdotal evidence suggests that this may be a problem in aquariums as well. Salt water aquariums designed to maintain coral reefs require high water flow and pristine water conditions, which in turn require pumps and filters that contribute to underwater noise. A survey of ambient noise in both fresh and saltwater aquariums ranging in size from 10 to 500 gallons was conducted. The aquariums differed in construction material, number, size and type of pumps, and presence of other equipment, and their ambient noise broadband levels are shown to vary widely.
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43.50.Cb Noise spectra, determination of sound power
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Shaped optimization of multi-chamber mufflers with open-ended perforated inlets using a genetic algorithm

Min-Chie Chiu and Ying-Chun Chang

POMA Volume 9, pp. 040003 (April 2010); (13 pages)

Online Publication Date: April 29, 2010

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Recently, research on new techniques of single-chamber mufflers equipped with a non-perforated intruding tube has been addressed; however, the research work on multi-chamber mufflers conjugated with open-ended perforated intruding inlet-tubes which may dramatically increase the acoustical performance has been neglected. Therefore, the main purpose of this paper is not only to analyze the sound transmission loss (STL) of a multi-chamber open-ended perforated inlet-tube muffler but also to optimize the best design shape within a limited space. In this paper, the four-pole system matrix for evaluating the acoustic performance - sound transmission loss (STL) - is derived by using a decoupled numerical method. Moreover, a genetic algorithm (GA), a robust scheme used to search for the global optimum by imitating a genetic evolutionary process, has been used during the optimization process. Results reveal that the maximal STL is precisely located at the desired tone. In addition, it has been shown that the acoustic performance for both pure tone and broadband noise will increase if the muffler has more chambers.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
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The near-field of spinning sources: Why source identification is hard

Michael Carley

POMA Volume 9, pp. 040004 (May 2010); (11 pages) | Cited 1 time

Online Publication Date: May 12, 2010

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An asymptotic analysis is presented for the near field of spinning sources, based on a transformation into cylindrical coordinates centred on a line at a fixed radius from the source axis. This transforms the circular source into an equivalent finite length line source with a source distribution made up of `modes' given as Chebyshev polynomials of the second kind. These `modes' play a role like that of modes in ducts and the analysis shows that their acoustic field propagates or decays depending on whether the mode order is less than, or greater than, wavenumber respectively, similar to the cut-on/cut-off behavior of duct modes. The analysis is used to examine the problem of identifying a source from field measurements. This has a wide range of applications and is recognized to be (very) ill-conditioned. Using the information supplied by the analysis of the source near field, the reasons for this ill-conditioning are explained.
Show PACS
43.20.Bi Mathematical theory of wave propagation
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.28.We Measurement methods and instrumentation for remote sensing and for inverse problems
43.50.Nm Aerodynamic and jet noise
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Noise mechanisms in motorcycle helmet noise

Michael Carley, Nigel Holt, and Ian Walker

POMA Volume 9, pp. 040005 (April 2010); (11 pages) | Cited 1 time

Online Publication Date: April 29, 2010

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A unique set of results on the acoustics of motorcycle helmets has been gathered during road tests on a rider wearing a representative modern helmet. The data were collected during a study of the noise which can cause hearing damage and, possibly, distraction in riders. They consisted of simultaneous measurements of noise at the rider's ear and unsteady pressure on the helmet surface, combined with GPS measurements of rider position and speed. These signals have been analyzed to educe the coherent structures in the turbulent flow responsible for noise generation. The identified structures appear to be produced by a vortex street shed by the motorcycle windscreen. The internal and external pressures proved to be poorly correlated over most of the frequency range, which has been identified as a result of the insertion loss of the helmet. The implications of these findings are that the majority of variation in helmet noise is a function of such extrinsic factors as motorcycle configuration and rider build and position. Efforts to reduce the harmful effects of noise in motorcycling should, then, move to studying the whole system of rider, helmet, motorcycle and external environment.
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43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.50.Ed Noise generation
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Qp Effects of noise on man and society
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Calculating annualized sound levels for a wind farm

Kenneth Kaliski and Eddie Duncan

POMA Volume 9, pp. 040006 (May 2010); (22 pages)

Online Publication Date: May 13, 2010

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Modeling done for wind farms usually focuses on calculating a worst-case short term average sound level. However, the impact to homes is not simply defined by a single meteorological condition. Rather, a more complete picture of the impacts is given by calculating sound levels under various meteorological conditions that occur during the year. The actual sound level at a receiver will depend on variations in atmospheric stability, wind speed, wind direction, and other parameters that change hourly. This paper will describe a method to calculate hourly sound pressure levels for individual receivers over the course of an 8760 h year and give examples of different wind farm configurations and how they affect annualized sound levels.
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43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
43.50.Vt Topographical and meteorological factors in noise propagation
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Interior Fourier Near-field Acoustical Holography Using Energy Density

Zachary A. Collins, Kent L. Gee, Scott D. Sommerfeldt, and Jonathan D. Blotter

POMA Volume 9, pp. 040007 (September 2010); (7 pages)

Online Publication Date: September 03, 2010

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Near-field acoustical holography (NAH) is used to reconstruct three-dimensional acoustic fields from a two-dimensional planar measurement. During previous work at BYU, a method has been developed called energy based near-field acoustical holography which reduced the number of needed measurements by 75%. Other recent advances have expanded the theory to interior spaces where multiple sources and/or reflections are present. This paper presents a new method for reconstructing interior acoustic parameters using Fourier NAH and a single plane of energy density measurements. Energy density is measured using a six-microphone array. First, the probe measurements are used to create a Hermite surface pressure interpolation on two separate planes. These two planes are used to approximate the normal particle velocity as well as to separate the incoming and outgoing waves using the spatial Fourier-transform method. Once separated, traditional Fourier NAH is used to reconstruct the pressure and normal particle velocity at any point in space. Analytical and experimental results are shown and compared to exterior Fourier NAH approximations. Other drawbacks and benefits are discussed.
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43.20.Ye Measurement methods and instrumentation
43.40.Sk Inverse problems in structural acoustics and vibration
43.50.Yw Instrumentation and techniques for noise measurement and analysis
43.60.Pt Signal processing techniques for acoustic inverse problems
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Quiet concrete pavement surfaces

Robert Rasmussen, Sabrina Garber, and Robert Whirledge

POMA Volume 9, pp. 040008 (October 2010); (11 pages)

Online Publication Date: October 19, 2010

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For the last five years, a comprehensive evaluation has been conducted on hundreds of concrete pavement surfaces throughout the US, Canada, and Europe. These data have been synthesized in a manner that allows the highway industry to make important decisions about how best to design and construct concrete pavements to reduce tire-pavement noise levels without compromising other important aspects such as durability, safety, and cost. While a significant amount of variability is present in the data, clear trends have been identified. Some surfaces, such as diamond grinding, appear to be among the best alternatives available today for reducing tire-pavement noise. Meanwhile, recent trials of more unconventional surfaces have yielded mixed results. In the end, the techniques for concrete pavement surfacing today include a vast array of choices. The selection of the best surface for the particular job can now be made more confidently given this improved understanding of the potential impacts due to tire-pavement noise.
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43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
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Near‐field acoustical holography applied to high‐performance jet aircraft noise

Alan T. Wall, Kent L. Gee, Michael D. Gardner, Tracianne B. Neilsen, and Michael M. James

POMA Volume 9, pp. 040009 (August 2011); (14 pages)

Online Publication Date: August 21, 2011

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Structural fatigue, hearing damage, and community disturbances may all result from jet noise, especially as jet aircraft become more powerful. Noise-reduction technologies require accurate characterization of the noise sources within jets. Array-based sound pressure measurements were made in the jet exhaust region of an F-22 raptor to allow for sound-field visualization using near-field acoustical holography (NAH). This is one of the largest-scale applications of NAH since its development in the 1980s, and the most detailed near-field measurements made of high-power jet noise to date. The measurement was made using a large, dense microphone array, which scanned sound pressures over several measurement surfaces near the jet, resulting in more than 6000 measurement points. Fixed reference microphones, measuring simultaneously with each scan, were used to perform partial field decomposition (PFD) of the measurement planes. Guidelines for multi-reference jet-noise measurements in current literature are qualitative at best. The PFD allows for an analysis of reference microphone requirements. A method for determining the adequacy of the reference array using near-field coherence measurements is examined. [Work supported by Air Force SBIR.]
Show PACS
43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.50.Nm Aerodynamic and jet noise
43.60.Sx Acoustic holography
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Portable loudspeaker coverage capability for in-situ outdoor performance spaces

Juan Arvelo

POMA Volume 9, pp. 040010 (August 2011); (11 pages)

Online Publication Date: August 26, 2011

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Observations from daily experiences reveal that sound propagation in air is influenced by the ground topography, atmospheric stratification, wind, and turbulence. A ray-based outdoor loudspeaker coverage model was developed that accounts for terrain and atmospheric conditions. Comparison against benchmark closed-form solutions and wave-based approaches demonstrate the accuracy and computational efficiency of this Gaussian-ray bundle model at aural frequencies. This model is well suited as an acoustic design aid for outdoor performance spaces and loudspeaker coverage may be adjusted for various levels of sound or speech intelligibility. The model was packaged into an ultra-mini notebook computer with an integrated GPS antenna and a 90-meter resolution worldwide terrain database to account for in-situ terrain effects on sound propagation, a built-in microphone for measurement of the background noise level and the loudspeaker source level, and a USB real-time monitor of temperature and relative humidity. The model is also capable of importing atmospheric measurement from balloon-launched radiosondes and various atmospheric models to accurately account for atmospheric stratification in temperature, pressure, relative humidity, wind speed and direction for both predictive and forensic investigations.
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43.20.Dk Ray acoustics
43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.28.Js Numerical models for outdoor propagation
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Innovative quieter aspirator design for in-car temperature sensor

Niranjan Humbad, Dan Silaghi, and Mike Morris

POMA Volume 9, pp. 040011 (May 2012); (9 pages)

Online Publication Date: May 03, 2012

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Automotive vehicles use aspirators to sense in-car temperature for controlling thermal comfort. The aspirator noise at the sensor end located on dash can be unacceptable and therefore an additional muffler is used between the sensor and the aspirator. A new innovative aspirator design was developed to replace the aspirator and muffler by a one piece design. This new concept was designed to meet the noise performance targets while making it easy to manufacture, while meeting the airflow targets of the current production two part aspirator and muffler design.
Show PACS
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.50.Nm Aerodynamic and jet noise
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
43.66.Lj Perceptual effects of sound
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