bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of acoustic context and scale resolution on judgments of voice quality
Authors: Kreiman Jody , Gerratt Bruce R. , Ito Mika , Antonanzas-Barroso Norma
Published: October 2013

Anchored protocols (in which listeners match test stimuli to fixed examples of different scale levels) control response variability in voice-quality judgment tasks, and may be clinically applicable because they are also easy to use. Successful application requires that two conditions hold. First, listeners must be able to isolate the target quality in the natural pathologic voice and match the level of that quality to levels present in a different acoustic context (the anchors). Second, the anchored scales resolution must be sufficient for listeners to make consistent judgments about stimuli that fall between anchors. To examine these issues, listeners judged noise levels for 40 test voices in four tasks. Two were anchored tasks (limited-scale resolution), in which the synthetic anchor voices matched the test voice (matched acoustic environment) in one condition and differed from the test voice environment in a second condition (traditional approach). Tasks three and four used the method of adjustment (fine-scale resolution). Listeners adjusted the noise level of a synthetic voice to match either that of an identical test voice, or that of a voice that differed from the test stimulus. Implications for theory and clinical practice will be discussed. [Research supported by NIDCD.]
Depth classification based solely on incoherent sonar information
Authors: Miklovic Donald W.
Published: October 2013

Most work on sonar contact depth estimation has been based on deterministic, coherent propagation modeling of the sound channel, e.g., matched-field processing. This has met with limited success due to the inability to precisely predict the sound-pressure field in realistic scenarios. This paper addresses the problem of using probabilistic, incoherent information from the sonar itself for depth classification with active sonar, without having to depend on precise and accurate propagation models and ancillary environmental measurements. In particular, the problem of deciding whether or not a given contact is on the bottom based solely on the sonar data is looked at, i.e., without resorting to the use of any additional environmental measurements or predictive models. To do this, the in situ local bottom reverberation is used to calibrate the channel. Probability theory is explored to provide a theoretical basis for the development of a single-hypothesis decision metric to best exploit this information. The methods are tested on a combination of broadband sonar data and detailed ocean simulations. The particular metric proposed for this problem seems to be important for achieving good performance, and may be of some interest in its own right for other types of single-hypothesis decision problems.
Source localization using the distribution of the interference invariant
Authors: Daly Peter M.
Published: October 2013

S.D. Chuprov’s ‘‘beta’’ parameter, or interference invariant, has been used to characterize low-frequency broadband acoustic propagation. Baggeroer showed the interference invariant was dependent on frequency, mode grouping, and environment. Rousseff and Spindel proposed representing the invariant as a distribution rather than a single parameter, as well as demonstrating via simulation how the invariant changed with receiver depth. This talk extends Rousseff and Spindel’s work to a shallow-water source localization problem. A method of incoherently combining broadband energy for passive source tracking in range and depth utilizing the distribution of the interference invariant as an observable from a single hydrophone will be illustrated, along with relevant performance metrics. [Work sponsored by SAIC.]
Ray-based acoustic localization applied in a highly reverberant environment
Authors: Chang Natasha A. , Dowling David R.
Published: October 2013

Acoustic localization techniques for finding and identifying broadband sound sources is of interest for studying low event rate cavitation, and other hydroacoustic noise sources, in water tunnels and other reverberant environments. The measured center frequency and bandwidth of the acoustic pulse from the collapse of a small isolated cavitation bubble are both approximately 100 kHz, and the measured pulse duration is ∼15−20 μs. Here, a sound projector is used to mimic such a pulse, and 16 receiving hydrophones are used to estimate the source location in the test section of a laboratory water tunnel when neither the timing of the event nor the exact signal waveform is presumed known. Fortunately, the direct-path signal arrival is generally distinct enough at each receiver for acoustic localization. The signal coda is not used in the present effort. The received direct-path signals are cross correlated between hydrophones to obtain arrival time differences. These arrival time differences are used in conjunction with a simple, straight-ray acoustic model to estimate the source location in three dimensions. Extension of this effort to use of first reflections and frequency domain modeling of the water tunnel for matched-field processing will be discussed as well. [Sponsored by ONR codes 333, 321.]
Rate distortion bounds for passive sonar performance
Authors: Meng Tianzhu , Buck John R.
Published: October 2013

Information theory provides a novel perspective on passive sonar. This approach begins by partitioning the search space and then considers the problem of assigning an unknown source to the correct partition based on pressure observations from a hydrophone array. The goal is to assign the source to the correct partition with the minimum possible probability of error (Pe). Prior work [Buck, Proc. IEEE SAM Workshop, 2002] described necessary conditions for achieving arbitrarily small Pe as a tradeoff between SNR and the range extent, or resolution, of the partitions. This paper presents a method to extend these results using rate distortion theory to find necessary conditions for any Pe, not just arbitrarily small ones. The Gaussian channel bound sets an upper limit on the rate of information received at the array, which implies a lower bound on Pe for a given partition. For a given range resolution, this method provides the minimum achievable Pe for a given SNR, or the minimum SNR to achieve a given Pe. Examples of these bounds will be given for typical shallow water environments. [Work supported by ONR Code 321US.]
Acoustic head waves in oceanic waveguides
Authors: Godin Oleg A.
Published: October 2013

Wave and ray theories of head (lateral) waves are reviewed, including effects due to absorption, stratification, source directivity, and roughness of interfaces. While the wave theory is instrumental in determining head-wave amplitude and region of existence, the ray theory of head waves is particularly helpful in extending results to multilayered structures and horizontally inhomogeneous environments. Physical significance of the head wave is discussed. As far as inverse problems are concerned, head waves offer a rather direct way of measuring certain physical and geometrical characteristics of the ocean bottom. Head waves typically have smaller amplitudes than other components of the acoustic field in a waveguide, but still can be reliably identified and measured, especially where they are spatially or temporally separated from the more energetic field components. Shallow-water environments are shown to complicate the arrival structure of head waves and their modeling, while providing additional opportunities for retrieving useful geoacoustic information from head-wave data. Application of the head-wave theory to determination of geoacoustic parameters of a stratified ocean bottom, including compressional wave attenuation, is illustrated using data obtained during the Pacific Shelf-93 experiment. [Work supported in part by ONR.]
Head waves, diving waves, and interface waves at the seafloor
Authors: Stephen Ralph A.
Published: October 2013

Brekhovskikh (1960) summarizes the system of waves that arises from reflection and refraction of spherical waves at the interface between homogeneous solid half-spaces. By eliminating the shear wave potential in one half-space, the system for fluid–solid half-spaces like the seafloor is obtained. There are two cases: one where the shear speed in the bottom is less than the compressional speed in the fluid (soft sediments), and the other where the shear speed in the bottom is greater than the compressional speed in the fluid (hard volcanic basement). This model is the basis for defining interface phenomena such as evanescent waves, head waves, pseudo-Rayleigh waves, and Stoneley/Scholte waves. If a positive gradient is introduced into the compressional and shear sound speeds in the bottom, one obtains diving waves and interference head waves (Cerveny and Ravindra, 1971). There are two types of interface waves: pseudo-Rayleigh waves that are evanescent in the bottom but propagate in the water, and Stoneley/Scholte waves that are evanescent in both media. In multi-interface models there are of course normal modes. In actual seafloors, low speed layers, sound and shear speed gradients, and interface and volume lateral heterogeneities affect the characteristics of propagation and scattering. [Work supported by ONR.]
Critical angle effects and their treatment using ray theory and mode theory
Authors: Westwood Evan K. , Penrod Clark S.
Published: October 2013

The interaction of the acoustic field from a point source with a fluid half-space is examined in terms of ray theory and mode theory. For ray theory, a complex ray approach [E. K. Westwood, J. Acoust. Soc. Am. 85, 1872–1884 (1989)] is used to find the reflected and transmitted fields as the sum of one or two eigenrays. The approach uses the method of steepest descent to solve the plane-wave integral for the fields, where the reflection and transmission coefficients are allowed to influence the locations of the saddle points and their steepest descent paths. As a consequence, saddle points are complex, and complicated processes such as the reflected lateral wave, beam displacement, and the transmitted evanescent field are included. For mode theory, the ORCA normal mode model [Westwood et al., J. Acoust. Soc. Am. 100, 3631–3645 (1996)] is used to illustrate the effects of the critical angle on the mode structure in a Pekeris waveguide. The Pekeris branch cut is shown to correspond to the lateral wave, and a method for replacing its branch line integral with a series of modes is described.
Range-dependent seismo-acoustics benchmark problems
Authors: Collins Michael D. , Jensen Finn B. , Nielsen Peter L. , Zampolli Mario , Schmidt Henrik , Siegmann William L.
Published: October 2013

Developing the capability to accurately solve range-dependent problems in ocean acoustics has been a topic of great interest for many years. At the time of the ASA benchmark efforts [J. Acoust. Soc. Am. 87, 1497–1545 (1990)], the elastic parabolic equation was in its early stages of development, and it was too early to consider problems involving shear waves. In recent years, there has been much progress in the development of parabolic equation and spectral techniques for range-dependent seismo-acoustics problems. The time is now ripe for extending the ASA benchmarks to cases involving shear waves. Several types of problems will be considered, including problems involving upslopes, downslopes, multiple solid layers, mode cutoff, and interface waves. [Work supported by the ONR.]
Extension of the variable rotated parabolic equation to problems involving variable topography
Authors: Collis Jon M. , Siegmann William L. , Collins Michael D.
Published: October 2013

Developing improvements in the capability of handling sloping interfaces and boundaries with the parabolic equation method has been an active area of research. The mapping solution [M. D. Collins and D. K. Dacol, J. Acoust. Soc. Am. 107, 1937–1942 (2000)] and the variable rotated parabolic equation [Outing et al., J. Acoust. Soc. Am. 115, 2579 (2004)] are among the recent advances in this area. The variable rotated parabolic equation, which handles variable bathymetry, is extended to solve problems involving variable topography. With this approach, the surface boundary is approximated in terms of a series of regions of constant slope. In each region, the parabolic equation is solved in a coordinate system that is aligned with the boundary. The junctions between regions are treated by overshooting the point at which the slope changes and interpolating and extrapolating to obtain a starting field in the next region. The mapping solution has been applied to some problems involving variable topography, but the variable rotated parabolic equation solution should provide greater accuracy, especially when there are relatively large slopes. [Work supported by ONR.]
Wave field and evanescent waves produced by a sound beam incident on a simulated sediment
Authors: Osterhoudt Curtis F. , Marston Philip L. , Morse Scot F.
Published: October 2013

When a sound beam in water is incident on a sediment at a sufficiently small grazing angle, the resulting wave field in the sediment is complicated, even for the case of flat, fluidlike sediments. The wave field in the sediment for a sound beam from a simple, unshaded, finite transducer has an evanescent component and diffractive components. These components can interfere to produce a series of nulls outside the spatial region dominated by the evanescent wave field. This situation has been experimentally simulated by using a combination of previously described immiscible liquids [Osterhoudt et al., J. Acoust. Soc. Am. 117, 2483 (2005)]. The spacing between the observed nulls is similar to that seen in a wave-number-integration-based synthesis (using OASES) for a related problem. An analysis of a dephasing distance for evanescent and algebraically decaying components [T .J. Matula and P. L. Marston, J. Acoust. Soc. Am. 97, 1389–1398 (1995)] explains the spacing of the nulls. [Work supported by ONR.]
Time-domain edge-diffraction calculations near zone boundaries
Authors: Calamia Paul T. , Svensson U. Peter
Published: October 2013

Time-domain edge-diffraction calculations are often used in studies of acoustic scattering from objects with rigid, simple-shaped surfaces, e.g., in computer simulations of room acoustics, noise-barrier performance, and radiation from loudspeakers. Many methods for such calculations are based on the Biot-Tolstoy solution, an explicit, continuous-time expression for diffraction by an infinite wedge. However, this expression contains two onset singularities which make numerical computations difficult: one which is present for all source-receiver combinations, and a second which occurs only when a receiver crosses a specular-zone or shadow-zone boundary, i.e., a boundary where a geometrical-acoustics component has a discontinuity. The former singularity was eliminated by Svensson et al. using a formulation in which the diffraction impulse response is expressed as a line integral along the diffracting edge [J. Acoust. Soc. Am. 106, 2331 (1999)]. In this paper, the latter singularity is addressed with analytical approximations of the formulation developed by Svensson et al. These approximations allow for accurate numerical computations for receivers at or near zone boundaries, and maintain a continuous total sound field when combined with geometrical-acoustics components. The approximations will be presented, along with a demonstration of modeling software into which they have been integrated.
Analysis of temporal decay of diffuse broadband sound fields in enclosures by decomposition in powers of an absorption parameter
Authors: Bliss Donald , Franzoni Linda , Rouse Jerry , Manning Ben
Published: October 2013

An analysis method for time-dependent broadband diffuse sound fields in enclosures is described. Beginning with a formulation utilizing time-dependent broadband intensity boundary sources, the strength of these wall sources is expanded in a series in powers of an absorption parameter, thereby giving a separate boundary integral problem for each power. The temporal behavior is characterized by a Taylor expansion in the delay time for a source to influence an evaluation point. The lowest-order problem has a uniform interior field proportional to the reciprocal of the absorption parameter, as expected, and exhibits relatively slow exponential decay. The next-order problem gives a mean-square pressure distribution that is independent of the absorption parameter and is primarily responsible for the spatial variation of the reverberant field. This problem, which is driven by input sources and the lowest-order reverberant field, depends on source location and the spatial distribution of absorption. Additional problems proceed at integer powers of the absorption parameter, but are essentially higher-order corrections to the spatial variation. Temporal behavior is expressed in terms of an eigenvalue problem, with boundary source strength distributions expressed as eigenmodes. Solutions exhibit rapid short-time spatial redistribution followed by long-time decay of a predominant spatial mode.
Exploratory research on acoustic design of multimedia classrooms
Authors: Zong F. D. , Zhang Z. L. , Fang J. W. , Yu Y. J. , Chen Q.
Published: October 2013

All kinds of multimedia classrooms can be found everywhere, especially in universities and schools. It is a pity that there are few multimedia classrooms with good acoustic quality, partly because these multimedia classrooms have been changed from common classrooms using some multimedia equipment. It is realized that an eligible multimedia classroom must meet many acoustic demands. These indexes are as follows: (1) how to assure the best reverberation time and frequency; (2) the integrated consideration of shape, direct sound, diffusion, early reflected sound, and ocular effect; (3) the audience’s sound absorption; (4) the room’s capacity. How to design an eligible multimedia classroom according to acoustic demands is discussed. This paper gives an overview of research into multimedia classroom acoustics, highlighting the importance of a good acoustic environment in universities and schools to enhance teaching and learning. The paper focuses on exploring research on reverberation time, early reflected sound, direct sound, and directivity of multimedia classrooms. There are some experience data and some advice based on examination and measurement. [Work supported by Zhejiang Nature Science Research Fund China.]
Hot topics: Signal processing in acoustics
Authors: Gaumond Charles F.
Published: October 2013

Signal processing in acoustics is a multidisciplinary group of people that work in many areas of acoustics. We have chosen two areas that have shown exciting new applications of signal processing to acoustics or have shown exciting and important results from the use of signal processing. In this session, two hot topics are shown: the use of noiselike acoustic fields to determine sound propagation structure and the use of localization to determine animal behaviors. The first topic shows the application of correlation on geo-acoustic fields to determine the Greens function for propagation through the Earth. These results can then be further used to solve geo-acoustic inverse problems. The first topic also shows the application of correlation using oceanic noise fields to determine the Greens function through the ocean. These results also have utility for oceanic inverse problems. The second topic shows exciting results from the detection, localization, and tracking of marine mammals by two different groups. Results from detection and localization of bullfrogs are shown, too. Each of these studies contributed to the knowledge of animal behavior. [Work supported by ONR.]
Hot topics in biomedical ultrasound: ultrasound therapy and its integration with ultrasonic imaging
Authors: Everbach E. Carr
Published: October 2013

Since the development of biomedical ultrasound imaging from sonar after WWII, there has been a clear divide between ultrasonic imaging and ultrasound therapy. While imaging techniques are designed to cause as little change as possible in the tissues through which ultrasound propagates, ultrasound therapy typically relies upon heating or acoustic cavitation to produce a desirable therapeutic effect. Concerns over the increasingly high acoustic outputs of diagnostic ultrasound scanners prompted the adoption of the Mechanical Index (MI) and Thermal Index (TI) in the early 1990s. Therapeutic applications of ultrasound, meanwhile, have evolved from deep tissue heating in sports medicine to include targeted drug delivery, tumor and plaque ablation, cauterization via high intensity focused ultrasound (HIFU), and accelerated dissolution of blood clots. The integration of ultrasonic imaging and therapy in one device is just beginning, but the promise of improved patient outcomes is balanced by regulatory and practical impediments.
Nanotech materials and how they can revolutionize underwater sensor coatings
Authors: Ramatowski Thomas S.
Published: October 2013

Most of the materials presently used to coat or encapsulate underwater acoustic sensors have been around for decades. The performance of these materials from a variety of perspectives can be characterized as barely adequate. Thus, these limitations have forced design engineers to accept many performance versus cost and/or service lifetime compromises. These compromises now threaten the viability of some of the U. S. Navy’s most cherished future hardware concepts, such as miniaturized, distributed sensors, large-area sensors/smart skins, and high-powered acoustic sources. Recent developments in nanomaterials and polymer nanocomposite technology suggest that a major advance in marine coatings and encapsulation technology would enable many of these concepts and initiatives to reach fruition. Because of the enormous surface area that a dispersion of such particulates possesses, relatively small loadings (typically a few weight percent) in a suitable polymer matrix may exhibit orders of magnitude-scale improvements in certain physical properties by influencing the structure of the polymer matrix in ways not possible to achieve with conventional technology. This presentation will review ongoing nanotech composite research at NAVSEA division Newport, and discuss the potential for nanotechnology to trigger a revolution in naval coatings and encapsulation technology in the next 3–5 years.
On the nonlinear models of the vibrating string
Authors: Watzky Alexandre
Published: October 2013

Vibrations of strings (threads, wires, cables...) are of great interest because of their various domains of application. In musical acoustics, phenomena which could have been neglected elsewhere take a particular importance since perception, which is very sensitive to nonlinear effects, is involved. Some phenomena can also be emphasized when a string is coupled to a sound-radiating structure. Reliable physical models are thus necessary to account for these phenomena, and to understand the true behavior of a vibrating string. Despite the fact that the first nonlinear models were published more than one century ago, and that accurate equations of motion can be naturally achieved within a finite displacement continuum mechanics framework, general models never received the attention they deserved, most authors focusing on particular phenomena and often settling on approximate models. This can be explained by the awkward multiplicity of the involved phenomena. The aim of this presentation is to discuss the consequences of some common assumptions and the true nature of some observed couplings. Particular attention will be paid to the preponderance of the spatial shape of the modes, which are usually underestimated with respect to their temporal form.
Unusual motions due to nonlinear effects in a driven vibrating string
Authors: Hanson Roger J.
Published: October 2013

Usual nonlinear effects observed in a sinusoidally driven vibrating string include generation of motion perpendicular to the driving plane, sudden jumps of amplitude and associated hysteresis, and generation of higher harmonics. In addition, under some conditions, there can be a rich variety of unusual, very complex motions of a point on the string, the pattern of which, together with associated harmonic (and sometimes subharmonic) content, can change dramatically with a slight change in driving frequency or sometimes with constant driving frequency and force. Intrinsic string asymmetries can also have a profound effect on the behavior. In a brass harpsichord string (wire) such asymmetries can cause a small splitting of each natural frequency of free vibration into two closely spaced frequencies (relative separation ∼0.2% to 2%, strongly dependent on tension.) The two frequency components are associated, respectively, with the transverse motion along two orthogonal characteristic wire axes. Emphasis will be on display of optically detected unusual motion patterns of a point on the string, including an example of a pattern period of 10 s when driving at 50 Hz. See R. J. Hanson et al., J. Acoust. Soc. Am. 117, 400–412 (2005) for a more complete treatment.
Simulation of the nonlinear vibration of a string using the cellular automata
Authors: Kawamura Shozo
Published: October 2013

In this study, the nonlinear dynamic responses of a string are simulated using the cellular automata (CA) method. The CA method is a discrete computation method, in which the analytical domain is divided into finite state variables called ecellsf and the state of each cell is updated according to local rules at every discrete time step. In this study, two types of local rule are used: the direct update rule and the reflection rule. In the case of nonlinear systems, the velocity of wave propagation is not constant and depends on the amplitude. A new treatment of the dynamic time step is proposed for the CA method considering the effect of the propagation velocity. As numerical examples, first the dynamic responses of a string with linear characteristic are simulated using the CA method. A typical resonance curve can be obtained. Second, the dynamic responses of a string with nonlinear characteristic are simulated using the proposed method. Some characteristic types of vibration can be obtained. It is concluded that the linear and nonlinear dynamic responses of a string may be obtained by simulation using the CA method.
Modeling of tension-modulated strings using finite difference and digital waveguide techniques
Authors: Pakarinen Jyri
Published: October 2013

Tension modulation is a nonlinear phenomenon where large-amplitude string vibrations cause the tension of the string to vary. This results in an initial pitch glide and energy coupling between modes, causing for example the generation of missing harmonics. The presentation discusses two methods for numerical simulation of the tension modulation nonlinearity from the sound synthesis point of view. The tension modulation is assumed to propagate instantaneously along the string. In the digital waveguide approach, spatially distributed fractional delay filters are used in modulating the string length during run time. Energy-preserving techniques can be used in implementing the fractional delays. In the finite difference approach, time-domain interpolation is used to artificially modulate the wave propagation velocity. The generation of missing harmonics is implemented in the finite difference model by creating an additional excitation point at the string termination. In the waveguide model, the same effect can be obtained by using suitable approximations in the string elongation calculation. Synthesis results for both techniques are presented. Also, a brief comparison of the models with a discussion on stability issues is provided. [This research has been funded by the Academy of Finland (Project No. 104934), S3TK graduate school, and Tekniikan edistamissaatio.]
The non-linear motion of harp strings
Authors: Waltham Chris , Chan Gary , Kotlicki Andrzej
Published: October 2013

The harp is an instrument with a set of plucked strings that excites the sound board directly, without the medium of a bridge. The strings are positioned at an acute angle to the plane of the sound board. The quality of the sound produced depends on the motion of the string and its interaction with the resonances of the sound board. The string and sound board motions of small and large harps have been studied using small, inexpensive infrared position sensors. The results are compared to those of a simple, nonlinear model based on the measured elastic properties of the string materials, and those of the sound board. The construction and calibration of the position sensors will also be described.
Community response to blast noise
Authors: Nykaza Edward T. , Pater Larry L. , Fidell Sanford , Schomer Paul
Published: October 2013

Although community response to impulsive noise from military operations is usually discussed for NEPA-related purposes in terms of the prevalence of annoyance, it is managed on a local, daily basis in terms of numbers of recent complaints. Reconciling blast noise complaint rates with the annoyance predicted by dosage-effect analysis would be of considerable benefit to the Army, since it would provide insight into the dynamics of community reaction to this distinctive form of noise exposure, and put its assessment and management on a common footing. This paper describes a systematic approach to the challenges of quantifying community reaction to blast noise. [Work supported by ERDC-CERL.]
Evaluation of small arms noise in a natural soundscape—Bear Butte, SD
Authors: Braslau David
Published: October 2013

Most studies on soundscape intrusion have been limited to moving sources. Of less concern is noise from small arms. Potential impact was predicted from a proposed large small arms facility with 10000 rounds or more per day on the natural soundscape at Bear Butte, one of the most sacred sites of the Northern Cheyenne and other tribes. The primary impacted activity is meditation and oneness with the natural environment that can continue for several days through day and night. Non-natural sources included limited vehicles on a nearby highway and farm equipment, but few aircraft. Second-by-second ambient octave band readings were taken at 20 sites starting before sunrise. The minimum ambient level observed was 19.6 dBA but limits were encountered with a 1/2 in. microphone. Sound level data on small arms were projected from the proposed range four miles north of Bear Butte to elevated points on the Butte assuming a zero wind environment. Impact was evaluated using audibility, intrusiveness and impulse-weighted DNL. Projected levels were well above ambient. While the DNL was projected to increase by 15 dBA, this metric has little meaning for this type of activity. Assumptions related to outdoor sound propagation, audibility and impulsive noise perception are discussed.
Assessment of community reaction to proposed club racetrack
Authors: Menge Christopher W.
Published: October 2013

The paper presents the approach and results of a study to assess the potential community reaction to a controversial proposed ‘‘club’’ racing and driver training facility in a rural community in the foothills of New Hampshire’s White Mountains. Commissioned by a municipal foundation, the study was to be neutral and balance the widely varying interests and concerns of all town residents. The study was also to assist the development of noise elements of a town ‘‘Race Track Ordinance,’’ in the absence of other noise regulations. Both existing community noise levels and noise emissions of comparable racing ‘‘car club’’ vehicles were measured, and are summarized in the paper. The local terrain, track layout and speed profiles were coded into SoundPLAN using ISO 9613-2 to compute summer-long Leq, leading to normalized DNL throughout the surrounding community as the primary metric for community reaction. Regularity of the audibility of racing on busy days was also estimated as an additi! onal metric. Based on these metrics, reaction was expected to be negative and widespread without such measures, therefore specific noise abatement measures and ordinance provisions were recommended and presented to the community at large and town officials.
Queuing for quiet—the natural soundscape microstructure from a visitor perspective—II
Authors: Horonjeff Richard D. , Anderson Grant S.
Published: October 2013

The passage of PL100-91 ‘‘The National Parks Overflights Act of 1987’’ and PL106-181 ‘‘The National Parks Air Tour Management Act’’ chartered the National Park Service (NPS) and Federal Aviation Administration (FAA) to restore ‘‘natural quiet’’ to park settings, especially those with lengthy occurrences of nonindigenous sounds. Since 1991, several field investigations have produced over 400 hours of source identification logs maintained by trained, audiometrically screened observers in a number of parks. The data acquisition protocol used a forced-choice, hierarchical menu structure with ‘‘audible source state’’ changes timed to the nearest second. This protocol provided the basis for examining the amount of time a visitor would have to wait (T) to experience a contiguous block of indigenous-only sounds of duration (D). This paper expands on an earlier presentation at the 148th Meeting of the Acoustical Society of America, 2004, by (1) presenting data from additional parks, (2) identifying the similarities and differences in findings within and across parks, (3) demonstrating the effects of terrain shielding, atmospheric propagation, and ambient masker sound levels, and (4) providing recommendations for employing the technique to achieve various park management objectives and its introduction into predictive models.
Another ‘‘new’’ metric for outdoor amphitheater criteria
Authors: Berens Robert S.
Published: October 2013

Since the late 1960s, when amplified musical performances began being held there, Atlanta’s open-air Chastain Park Amphitheater has been the source of enormous friction between the City, the venue’s owner, and the wealthy, politically-connected residential community abutting the Park. To identify the characteristics of concert event sound to which neighbors are particularly sensitive, sound levels were monitored during 17 concerts, ranging from quiet jazz and classical performances to rock-and-roll and hip-hop. Community sound levels were monitored at 25 locations, including nine where measurements were made simultaneously inside and outside homes. The study team confirmed that low-frequency sound was the one feature of concert-related sound that community residents identified as most problematic, but that only a relatively small proportion of the Chastain concerts resulted in any significant community annoyance. After assessing the spectral characteristics of the most troublesome concerts, a new compliance metric has been proposed to address low-frequency annoyance issues: a two-tiered exceedence threshold, based on 1-minute LEQ levels in the 63 Hz octave band measured at the rear of the amphitheater, with a concert-event ‘‘exceedence’’ defined to be either a 1-minute LEQ(63 Hz) level greater than 95 dB or more than ten 1-minute LEQ(63 Hz) levels greater than 90 dB.
A study on construction equipment noise
Authors: Alur Ramachandraiah
Published: October 2013

In India, the construction industry is one of the major industries comprising huge manpower and equipment. Currently the government is focusing on infrastructure development for projects such as expanding highways, construction of buildings, and various other activities. This paper is focused toward the noise and vibration generated by such construction equipment, and stresses the requirement for a standard code for noise control. The sites covered are construction sites such as highway expanses, construction of various buildings, and also operations involved in ground-leveling techniques. It is noticed that the noise levels from various sources exceed the acceptable limits generally suggested. Some of the pile-driving operations generate noise levels of the order of 108 dBA and pneumatic tools generate 85 to 90 dBA in the site. A questionnaire survey is also carried out by many of these companies to evaluate the opinion of the user from the noise and vibration viewpoint. The majority (59%) complains that noise and vibration have to be mitigated. However, as Indian industries have to comply with many international standards, it becomes imperative to arrive at acceptable standards. In this context a discussion has been carried out.
Case studies of pre-engineered and manufactured sound isolation rooms for music practice and radio broadcast
Authors: Probst Ron N. , Rypka Dann
Published: October 2013

Pre-engineered and manufactured sound isolation rooms were developed to ensure guaranteed sound isolation while offering the unique ability to be disassembled and relocated without loss of acoustic performance. Case studies of pre-engineered sound isolation rooms used for music practice and various radio broadcast purposes are highlighted. Three prominent universities wrestle with the challenges of growth and expansion while responding to the specialized acoustic requirements of these spaces. Reduced state funding for universities requires close examination of all options while ensuring sound isolation requirements are achieved. Changing curriculum, renovation, and new construction make pre-engineered and manufactured rooms with guaranteed acoustical performance good investments now and for the future. An added benefit is the optional integration of active acoustics to provide simulations of other spaces or venues along with the benefit of sound isolation.
Combination sound and vibration isolation curb for rooftop air-handling systems
Authors: Paige Thomas S.
Published: October 2013

This paper introduces the new Model ESSR Sound and Vibration Isolation Curb manufactured by Kinetics Noise Control, Inc. This product was specially designed to address all of the common transmission paths associated with noise and vibration sources from roof-mounted air-handling equipment. These include: reduction of airborne fan noise in supply and return air ductwork, reduction of duct rumble and breakout noise, reduction of direct airborne sound transmission through the roof deck, and reduction of vibration and structure-borne noise transmission to the building structure. Upgrade options are available for increased seismic restraint and wind-load protection. The advantages of this new system over the conventional approach of installing separate duct silencers in the room ceiling space below the rooftop unit are discussed. Several case studies are presented with the emphasis on completed projects pertaining to classrooms and school auditorium applications. Some success has also been achieved by adding active noise control components to improve low-frequency attenuation. This is an innovative product designed for conformance with the new classroom acoustics standard ANSI S12.60.
The challenges of lawnmower noise reduction
Authors: Drutowski Carol J. , Fetzer Keith
Published: October 2013

The European Noise Directive (2000/14/EC) became effective in the year 2000, limiting the allowable noise level for lawnmowers sold in the European Union. Noise level limits are based on cutting width. The Directive requires that manufacturers meet these limits and include statistical uncertainties, then declare their noise levels and have these results certified by an independent third party agency. There are two major challenges with this Directive. First by taking statistical uncertainties into account, this creates a limit lower than the published limit. Second is to lower the sound power level while still maintaining acceptable performance. The physical phenomena that generate the unwanted noise of a lawnmower are also used to perform work. For rotary lawnmowers, a dominant noise source is the cutting deck assembly, which is required to lift and cut grass, then dispose of the clippings. To cut grass with a good quality of cut appearance, the blades are required to turn at a very high tip speed to generate the necessary airflow. For lawnmowers, noise levels and unit performance are intrinsically linked. This has frustrated our industry for over 20 years.
Acoustic emissions verification testing of International Space Station experiment racks at the NASA Glenn Research Center Acoustical Testing Laboratory
Authors: Akers James C. , Passe Paul J. , Cooper Beth A.
Published: October 2013

The Acoustical Testing Laboratory (ATL) at the NASA John H. Glenn Research Center (GRC) in Cleveland, OH, provides acoustic emission testing and noise control engineering services for a variety of specialized customers, particularly developers of equipment and science experiments manifested for NASA’s manned space missions. The ATL’s primary customer has been the Fluids and Combustion Facility (FCF), a multirack microgravity research facility being developed at GRC for the USA Laboratory Module of the International Space Station (ISS). Since opening in September 2000, ATL has conducted acoustic emission testing of components, subassemblies, and partially populated FCF engineering model racks. The culmination of this effort has been the acoustic emission verification tests on the FCF Combustion Integrated Rack (CIR) and Fluids Integrated Rack (FIR), employing a procedure that incorporates ISO 11201 (‘‘Acoustics–Noise emitted by machinery and equipment–Measurement of emission sound pressure levels at a work station and at other specified positions–Engineering method in an essentially free field over a reflecting plane’’). This paper will provide an overview of the test methodology, software, and hardware developed to perform the acoustic emission verification tests on the CIR and FIR flight racks and lessons learned from these tests.
Characterization of vibration and noise exposure in Canadian Forces armored vehicles
Authors: Nakashima Ann M. , Borland Matthew J. , Abel Sharon M.
Published: October 2013

A study to characterize the vibration and noise exposure in several Canadian Forces (CF) armored vehicles is in progress. Measurements of whole-body vibration and ambient noise levels are being made in the LAV III, Bison, Coyote, and M113 vehicles at three different positions: driver, crew commander, and passenger bench (or navigator seat in the case of the Coyote). The measurements are being made while the vehicles are idling, driven over rough terrain, and driven at a high speed on paved highways. There are several standards that provide guidance on the measurement and assessment of whole-body vibration, but they are difficult to implement in practice, particularly in adverse environments. The whole-body vibration measurements in this study are particularly difficult to interpret in the case of the crew commander, who often stands on the seat, and the passenger, who is seated but unrestrained by a seatbelt. The preliminary results-suggest, that according to the International Organization for Standardization guidelines (ISO 2631-1:1997), there may be potential health risks for the driver and passenger after driving on rough terrain for less than 10 min. Noise levels were as high as 100 dBA during high-speed highway driving.
Noise exposure in marching bands
Authors: Keefe Joseph
Published: October 2013

Previous studies involving orchestras have shown that music ensembles can produce hazardous noise levels. There are no similar data for marching bands and pep bands. In order to evaluate the noise levels produced by marching and pep bands, 1/3-octave-band sound-pressure levels were measured while these groups rehearsed and performed. Data were collected while marching with the bands to ensure a realistic environment. Comparing these data to OSHA and NIOSH criteria, marching and pep band exposures often exceed safe values. For typical exposures, OSHA doses range from 11% to 295%, while NIOSH doses range from 35% to 3055%. Exposures that would be considered hazardous in the workplace are common in marching and pep bands; students and band directors should take steps to recognize the risk posed by various instruments and various locations, and should implement hearing conservation efforts.
Creative reflections—the strategic use of reflections in multitrack music production
Authors: Case Alexander
Published: October 2013

There is a long tradition of deliberately capturing and even synthesizing early reflections to enhance the music intended for loudspeaker playback. The desire to improve or at least alter the quality, audibility, intelligibility, stereo width, and/or uniqueness of the audio signal guides the recording engineer’s use of the recording space, influences their microphone selection and placement, and inspires countless signal-processing approaches. This paper reviews contemporary multitrack production techniques that specifically take advantage of reflected sound energy for musical benefit.
Sound-pressure level distribution in a long, narrow hallway: Measurements versus results from a computer model with scattering from surface roughness and diffraction
Authors: Wang Lily M. , Rathsam Jonathan , Christensen Claus L. , Rindel Jens H.
Published: October 2013

The sound-pressure level distribution down a long, narrow hallway due to a sound source at one end does not decrease linearly along the length of the hall. This characteristic may be due to the changing behavior of scattering that occurs down the length of the hallway, which is distance- and angle-dependent. A new scattering method that incorporates these effects has been implemented in the room acoustic computer modeling program, odeon [C. L. Christensen and J. H. Rindel, Forum Acusticum, Budapest (2005)]. A comparison of the results from an odeon model with real-world measurements along a long, narrow hallway on the campus of the Technical University of Denmark is provided in this paper. [Work supported by the NSF.]
Surface characterization from the point of view of an acoustical consultant
Authors: Pfeiffer Scott D. , Ament Jacob , Belanger Zackary , Norris Molly , Gulsrud Tim
Published: October 2013

The practical characterization of the acoustical properties of absorption, diffusion, and transparency of surfaces is an area where the application of physical acoustic techniques may be more applicable than typical architectural acoustical parameters. Understanding the diffusive behavior of surfaces is crucial to the design of spaces, but cumbersome to quantify, requiring different techniques depending on the question being asked. Past studies conducted by Kirkegaard Associates on products for partial reflection, diffusion, nominal transparency, and the results of a recent implementation of the current proposed Audio Engineering Society standard AES-4id-2001 are discussed with respect to the need to make design decisions and implement products for fulfillment of an acoustic design process. The viability of using a single-valued diffusion coefficient is discussed with respect to the needs of the acoustical consulting community, while still exploring the possibility of alternative characterization methods.