bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher order acoustic diffraction by edges of finite thickness
Authors: Chu Dezhang , Stanton Timothy K.
Published: October 2013

Generalized temporal and spectral solutions of acoustic diffraction by edges of finite thickness involving higher orders diffraction are presented. The solution in the time domain is an extension of Medwins double-edge second-order diffraction solution [H. Medwin et al., J. Acoust. Soc. Am. 72, 1005–1013 (1982)], which is based on the Huygens principle, while the solution in the frequency domain is an extension of the asymptotic formulas for the double-edge second-order diffraction via amplitude and phase matching given by Pierce [A. D. Pierce, J. Acoust. Soc. Am. 55, 943–955 (1974)]. Since both solutions are approximate they have different advantages and disadvantages. The contribution from higher order diffraction depends strongly on the thickness and geometry of the edges. Comparison between the theory and experimental diffraction data demonstrates that for edges of finite thickness, the first order diffraction alone under-estimates the total diffraction field significantly, especially when the flat end of the two edges directly faces the transducers (i.e., edge-on incidence). [Work supported by ONR.]
Decomposition of the time reversal operator applied to subwavelength localization of scatterers
Authors: Minonzio Jean-Gabriel , Prada Claire , Fink Mathias , Aubry Alexandre
Published: October 2013

The decomposition of the time reversal operator (DORT method in French) is an ultrasonic detection method based the analysis of the whole pulse echo responses of an array. The eigenvalues and the eigenvectors of the time reversal operator (i.e., singular values and singular vectors of the array response matrix) provides information on localization of scatterers in the insonified medium. Recent experiments shows how DORT can also be used as a characterization method of subwavelength scatterers as cylinders [Minonzio et al., J. Acoust. Soc. Am. accepted May (2004)]. It has been shown that multiple singular values are associated with a single scatterer and that the singular vectors are combinations of the normal modes (monopole, dipole) of vibrations. In this study, interactions between two subwavelength cylinders less than a wavelength apart are described. Multiple scattering affects the singular value distribution. Experiments and calculations have been carried out on nylon and metal cylinders with diameters ranging from 0.07 to 0.2 mm. The central frequency is 1.5 MHz, and the scatterers are 5 cm away from the array. The estimator multiple signal characterization (MUSIC) is used for subwavelength localization of scatterers [Prada et al., J. Acoust. Soc. Am. 114, 235–243 (2003)].
Experimental and analytical investigation of surface ship hull structural acoustics using physical models
Authors: Craun Matthew A. , Diperna Daniel P. , Carroll Gerald P. , Martin William J. , Corrado Charles N. , Abraham Bruce M.
Published: October 2013

An experimental and analytical investigation was undertaken to characterize surface ship structural acoustics. LDV scans were made of scale models representing midhull sections of conventional and double-hull ship designs. The models were placed in a reverberant tank and excited at multiple points with tankage empty and full of water. In addition to LDV scans, hydrophones were utilized to measure radiated power. Local and global hull response for the models were examined and compared up to a frequency of 5 kHz. Hull response was further processed to determine the supersonic velocity components. Wave number analysis was conducted to characterize wave-type propagation along the hull structure. Periodic highlights were observed for wave aliasing due to bulkheads and hull stiffeners. Theoretical models were developed and exercised to develop an understanding of the experimental data. The experimental effort provides a data set to verify numerical tools. The combined experimental and theoretical modeling efforts provide a foundation to develop concepts for acoustic signature control.
Vibratory response of surface ships predicted by energy finite element approach
Authors: Wu Kuangcheng , Vlahopoulos Nickolas
Published: October 2013

Energy finite element analysis (EFEA) and energy boundary element analysis (EBEA) have been successfully developed and validated for a submerged plate and a cylindrical shell (Zhang et al., J. Sound Vib. 263, 21–46) and have been applied to calculate flow noise of a submerged cylindrical shell under turbulent boundary layer excitation (K. Wu and N. Vlahopoulos, ASA 143rd Meeting). Recently, new capabilities are under development to extend EFEA/EBEA formulations for surface ship applications. The presentation will discuss the developmental work and present some numerical examples in validating the development. [Work Support for this research is provided by ONR Code 334.]
Development of ship radiated noise transfer functions and near-field to far-field measured signature comparisons
Authors: Fischer Raymond , Boroditsky Leo
Published: October 2013

Various methods exist to determine the vibration level on the wetted hull plate of a vessel—whether they be measured or predicted. Transfer functions are discussed that relate the hull vibration levels and ship’s physical parameters to the far-field radiated noise. These methods are useful to predict the noise from fisheries research vessels and other vessels such as work or cruise boats. The former need to ‘‘sneak-up’’ on fish to perform stock assessment and the latter may need to operate in environmentally sensitive areas. Predicted radiated noise is compared to measured noise to assess the accuracy. Data is also presented on measured noise data for several vessels at various separation distances approximating near- and far-field conditions. These data were taken with the vessel at zero speed.
Hybrid deterministic-statistical modeling of stiffened plate structures
Authors: Lande Rolf H. , Langley Robin S. , Woodhouse Jim , Shorter Philip J.
Published: October 2013

Statistical energy analysis (SEA) is based on equations of power balance between resonant subsystems, and, given the excitation power input to the system, the resulting average vibration level in each subsystem may be calculated. However, due to the low modal density of beams, SEA cannot fully account for energy flow along stiffening members of typical stringer-skin constructions used in the aerospace and marine industries. Thus, in a conventional SEA model of a built-up structure to which excitation is applied through a stiffening member, it is not clear how to compute the power input to each resonant subsystem and the response of the nonresonant stiffening framework. The problem is addressed by using a coupled deterministic-statistical approach: the stiffeners are modeled deterministically, while the reverberant two-dimensional structural components are modeled as power absorbing systems, in which the power is carried by statistical cylindrical waves propagating towards an energy sink. This power is then reinjected into an SEA model of the system. The numerical features of the method and some new results from a beam-plate system (compared with Monte Carlo simulations) are presented. The results indicate that the SEA power input as well as the response of the stiffener is modeled correctly.
Effects of fluctuating shear stresses on the low wave number wall pressure spectrum
Authors: Hwang Y.-Fan
Published: October 2013

The well-known Kraichnan–Phillips theorem states that the low wave number spectrum of the wall pressure on a smooth wall beneath an incompressible and inviscid turbulent boundary layer flow is proportional to the square of wave number, and the limiting value of the spectrum is zero as the wave number approaches zero. In practice, however, measurements do not support this theoretical conclusion from ideal fluids. A theory on the possible contributions by the fluctuating viscous shear stresses to the nonvanishing pressure spectrum at zero wave number has been discussed in the literature [D. M. Chase, ‘‘Fluctuations in wall-shear stress and pressure at low streamwise wave numbers in turbulent-boundary-layer flow,’’ J. Fluid Mech. 225, 545–555 (1991)]. Preliminary evidence to support the theory, based on the result of comparing measured near-zero wave number wall pressure and shear stress spectra, is discussed in this paper. [Work supported by ONR, Code 333.]
Examining the role of nonadjacent phonotactic dependencies in the perception of spoken language
Authors: McLennan Conor T. , Luce Paul A. , LaVigne Robert
Published: October 2013

At the previous ASA meeting we presented results on experiments investigating the learning of nonadjacent phonotactic dependencies in the perception of spoken language. Previous research had provided evidence for the learning of nonadjacent dependencies at a grammatical level (e.g., Gomez, 2002). Our research examined whether such learning was possible at a phonological level. Each learner was exposed to CVC nonword stimuli produced by one of two artificial languages. Both languages contained the same adjacent dependencies so learners could only distinguish the languages by acquiring dependencies between the initial and final Cs (i.e., the nonadjacent dependencies). Our results demonstrated that subsequent perception was facilitated for stimuli with the same nonadjacent phonotactic dependencies. In the current study, we extended this line of research by evaluating the role of nonadjacent phonotactic dependencies in nonwords that had been lexicalized. In particular, we asked whether the previous effect of facilitation would now manifest itself as inhibition, presumably due to the competition between lexicalized items sharing nonadjacent phonotactic dependencies.
Perception of the English tense/lax vowel contrast by native speakers of Russian
Authors: Kondaurova Maria V. , Francis Alexander L.
Published: October 2013

The present study examined the effect of native language background on the perception of American English tense and lax front unrounded vowels ([i] and [I]). These vowels are distinguishable according to both spectral (vowel quality) and temporal (vowel duration) properties. Nineteen native Russian and 12 native American English listeners identified stimuli from a two-dimensional beat-bit continuum varying in 10 spectral and nine duration steps. English listeners used predominantly spectral quality when identifying these vowels, but also showed some reliance on duration cues. In contrast, Russian listeners failed to employ vowel quality to differentiate English tense and lax vowels which can be explained by their assimilation to the same Russian /i/ phoneme in a ‘‘single category assimilation’’ process (Best, 1995). Instead, they relied almost entirely on the duration cue, despite the absence of distinctive vowel length in Russian. These results could be interpreted as supporting the desensitization hypothesis (Bohn, 1995): When spectral differences are insufficient to distinguish a non-native vowel contrast, duration will be employed by default. Alternatively, the strength of Russian listeners’ reliance on duration may instead reflect the influence of prior experience with subphonemic duration contrasts within the lexical stress system of the Russian language.
Auditory training with phonetic variability and acoustic enhancement: A comparison of /r/–/l/ training techniques for Japanese adults
Authors: Iverson Paul , Bannister Kerry , Hazan Valerie
Published: October 2013

High-variability phonetic training (HVPT) techniques have been successful for helping Japanese adults learn the English /r/–/l/ distinction. This success has been attributed to the fact that HVPT exposes listeners to naturalistic phonetic variability, from many talkers and phonetic contexts [e.g., Logan et al., J. Acoust. Soc. Am. 89, 874–886 (1991)]. The present investigation examined whether naturalistic phonetic variability is essential for effective training. HVPT (natural recordings from ten talkers) was compared with three conditions, in which signal processing was used to alter the phonetic variability of these natural recordings: all enhancement (F3 set to extreme values); perceptual fading (amount of F3 enhancement progressively decreased during training); and secondary cue variability (variability in F2 and duration cues progressively increased during training). The results thus far suggest that all of these training techniques were similarly effective, improving /r/–/l/ identification by an average of 15–20 percentage points for Japanese adults. It appears that the presence of naturalistic phonetic variability may not be critical to the effectiveness of HVPT. [Work supported by ESRC.]
L2 speakers’ recognition memory for English sentences with prosodic cues
Authors: Choi Eun-Suk
Published: October 2013

This study investigated L2 learners’ recognition memory for English sentences with prosodic cues and examined the effect of English proficiency on recognition memory for English prosody. Twenty Korean L1 speakers and ten English L1 speakers participated in two tasks. The Korean L1 speakers were grouped according to their proficiency level: 10 each for high and low proficiency level. In a discrimination task, participants’ attention was explicitly focused on the contrasts in prosody and the associated differences in meaning, followed by a recognition task that tested whether prosodic cues were used to recognize the sentences. The results demonstrated that high-proficiency L2 speakers of English were better at using prosodic cues to interpret spoken sentences and remembering their meaning accordingly than low-proficiency L2 speakers. High-proficiency L2 speakers showed better recognition memory of the prosodic content of English sentences than for their lexis, while low-proficiency L2 speakers were better with the lexical content than prosodic cues. Native speakers and high-proficiency L2 speakers of English did not differ in recognizing meaning differences cued by prosody. However, high-proficiency L2 speakers of English were significantly worse at rejecting sentences containing lexis that they had not heard than L1 speakers.
Acoustic backscatter at very high frequencies from rough seabeds
Authors: Brothers Richard J. , Heald Gary J. , Robb Gary , Leighton Timothy G. , Dix Justin
Published: October 2013

Acoustic backscatter data were gathered from a variety of seabed types, both in the laboratory tank and in coastal waters. Data were gathered from sandy sediments in the tank, with a variety of characterized rough surfaces, using narrow-band pulses at frequencies between 100 and 950 kHz. Wideband data gathered at sea were obtained at frequencies between 80 and 650 kHz. Data gathered at sea from the Acoustic Range at QinetiQ Bincleaves included backscatter from the natural sandy seabed, but also scatter from several artificial sediments (sand, gravel, and pebbles) placed in a rotator. The latter equipment allowed acoustic interrogation of the same patch of seabed from multiple angles. Experimental data are compared with fluid, poroelastic, and discrete scatterer models, with a view to recommendations for the modeling of seabed backscatter in the frequency band 100 kHz to 1 MHz.
The small slope approximation+(S
S
A+) for rough surface scattering
Authors: Broschat Shira L. , Wang Yanqiu
Published: October 2013

To be practical, a rough surface scattering model must be easy to implement and easily incorporated into existing models. At the same time, it must be accurate enough to give useful results. Here ‘‘practical’’ is defined to mean (1) no more than N-D integration away from low grazing angles, where N represents the dimension of the surface, (2) no more than 2N-D integration at low grazing angles, and (3) accuracy to within a few dB. In previous work it was shown that at low forward grazing angles an approximation to the nonlocal small slope approximation (NLSSA) satisfies the first and third criteria but not the second. It was also shown that the NLSSA cross section can be written as the sum of the lowest-order SSA cross section and an additional term, the latter of which can be considered a correction term for the lowest-order SSA. In this paper the SSA+, which is based on the NLSSA but includes three approximations to the correction term, is presented. The SSA+ satisfies all three criteria for a ‘‘practical’’ scattering model at low forward grazing angles. Numerical results are presented. [Work supported by ONR.]
Scintillation index of ocean surface forward scattered HF acoustic signals
Authors: Cotté Benjamin , Bradley David , Culver R. Lee
Published: October 2013

The intensity fluctuations of surface bounce path measured during a field test near San Clemente Island in August 2002 are presented. Signals used are CW pulses with 0.14- and 1.0-ms durations and FM sweeps with 1-, 7-, 13- and 22-kHz bandwidth centered at 20 and 40 kHz. Source and receiver were separated by about 700 m with source depth ranging from 10 to 67 m and receiver depth ranging from 44 to 217 m. Data were collected over a 5-day period for low sea states (0 to 1). The dependence of the surface bounce path scintillation index on frequency, grazing angle, pulse length and bandwidth has been estimated. The results are then compared with an existing model based upon the correlation function of the ocean wave spectrum. Scatter of the data about the model is being investigated from the standpoint of other parameters. [Work supported by ONR Code 321US.]
A comparison of laboratory reflection coefficient data with predictions from a time domain model of sea floor scatter using the small slope approximation (BoRIS-SSA)
Authors: Isakson Marcia , Canepa Gaetano , Pouliquen Eric
Published: October 2013

Reflection coefficient data has the potential for sediment model verification and remote sensing of sediment parameters. However, a significant component of the bistatic acoustic response is scattering from the rough interface. For example, in typical ocean conditions, surface roughness can alter the apparent normal reflection coefficient by 15 dB or more over a frequency range from 10 to 100 kHz. Therefore, it is important to quantify the contribution from scattering to determine the smooth surface reflection coefficient from bistatic data. The Bottom Response from Inhomogeneities and Surface (BoRIS-SSA) code uses the small slope approximation to calculate bistatic response from rough surfaces. BoRIS-SSA can incorporate both stochastic realizations of the ocean bottom or data from stereo-photographic equipment. In this study, bistatic laboratory data taken at 50–150 kHz from a smoothed and roughened interfaces will be compared to BoRIS-SSA calculations. The model will be considered for its ability to predict both the average value of the bistatic response and the distribution of the data.
Backscattering by a partially submerged circular cylinder at grazing incidence
Authors: Baik Kyungmin , Marston Philip L.
Published: October 2013

It is not trivial to use ray theory to describe backscattering by partially submerged or partially buried targets because in many cases of interest, Fresnel zones associated with specular points are not fully exposed and there are transitions in the number of rays when more of the target is illuminated. The Kirchhoff approximation for a partially illuminated cylinder has been used for normal incidence [P. L. Marston, J. Acoust. Soc. Am. 114, 2302 (2003)]. The present work concerns the application and testing of the Kirchhoff approximation for a partially submerged cylinder at grazing incidence. The Kirchhoff approximation removes the singularities of elementary ray theory. For a cylinder illuminated broadside near 30° grazing angle the backscattering amplitude evolves in a non-monotonic way as the cylinder is lowered through the air–water interface. When backscattering measurements are taken in such a way that only specular contributions are included, the evolution of many (but not all) of the observed features is accounted for. The measurements typically have ka near 13. [Work supported by ONR.]
The computation of rough surface scattering from a finite interval of roughness
Authors: Fawcett John A.
Published: October 2013

The computation of scattering from a rough, pressure-release surface is a problem of much interest in many applications. In this paper, the exact numerical solution of scattering from a finite interval of roughness is considered. This interval is a portion of an otherwise flat surface that is infinite in extent. One numerical approach is to consider a truncated infinite integral equation. However, unless one is willing to use large computational intervals, perhaps far exceeding the extent of the roughness, the solution to the truncated problem may not approximate the infinite interval solution very well for some situations. In this paper, a system of equations is derived for a closed curve including the interval of roughness and a portion of the curve in the surrounding fluid. The system is solved using the method of wavefield superposition. The method is applicable to the case of both positive and negative deformations of the flat surface. As well, the method is easily extendable to the case that the roughness is part of an upper surface of a waveguide.
Time reversal of interface reverberation
Authors: Lingevitch Joseph F. , Roux Philippe
Published: October 2013

Bottom reverberation can be used as a probe-source of opportunity to construct a time-reversal focus that scans along a rough interface. We present results from a tank experiment at ultrasonic frequencies in which reverberation from a sandy bottom was collected on a 64-element source/receiver array. The monostatic reverberation measurements are windowed, time-reversed, and then transmitted. When measureable backscatter is present in the time window, energy is observed to focus at a range corresponding to that window. Two factors contribute to the back-scattered energy level: first, the propagation paths for a particular incident ping will nonuniformally ensonify the interface and, second, the local interface scattering strength will vary with range. A method to capture reverberation at all ranges and an application to realistic shallow water ocean waveguides are also presented.
Grappling with pithy problems: The education in acoustics of John William Strutt (aka Lord Rayleigh) and of the rest of us
Authors: Pierce Allan D.
Published: October 2013

There is a little of Rayleigh in each of us, so we might benefit from some selective emulation, and educators might adopt some of the stimulations that contributed to Rayleigh’s success. As a child, Rayleigh loved dabbling in scientific experimental projects, but his formal education was greatly influenced by the contemporary view that mathematics was a respectable alternative to the classics. When he entered Cambridge, he was ‘‘decidedly less advanced in mathematical skills than the best of his contemporaries,’’ but this situation changed, largely due to the stimulus of the Cambridge environment, to an intrinsically competitive nature, and to the influence of one of the greatest educators of all time—Edward John Routh. Rayleigh was coached to solve problems, and he excelled at this. After graduation, Rayleigh embarked on a program of self-education and developed a strategy for combining his love of experimentation with his more recently acquired problem-solving skills. Details of this self-education are related. Extensive illustrations are given of problems such as might have been presented to Rayleigh as a student, such as he might have presented to students himself, and such as might to good purpose be presented to acoustics students of today.
Hot topics in architectural acoustics: Practice and research
Authors: Hoover K. Anthony , Kleiner Mendel
Published: October 2013

Architectural acoustics is concerned with all aspects of sound in and around buildings. The first part of the talk will address practical and applied topics that include footfall and impact sound isolation (especially floor underlayments), health care facilities (especially MRI noise and vibration control), learning-spaces acoustics (including the recent standard, ANSI S12.60.2002), and health and safety issues of ‘‘acoustical’’ products (including duct lining and flame/toxicity issues for sound-absorptive materials). An overview will also be presented of the National Council of Acoustical Consultants (NCAC) ‘‘Member Forum,’’ which is a members-only on-line forum for discussion and new information, specifically for acoustical consulting. The second part of the talk will focus on current research issues in architectural acoustics worldwide as mirrored by recent conventions, conferences, and meetings, such as the German Acoustical Society (DEGA), the Institute of Acoustics (IoA), and the International Congress on Acoustics (ICA) with special emphasis on auralization and scattering.
Fluctuations as a measure of frequency ratios in equally tempered scales
Authors: Sevgen Alpar
Published: October 2013

Complexity analysis of equally tempered scales (ETS) and the dynamic models that mimic this analysis indicate that tones tend to stay as far apart from each other as possible in scales employed in music. A quantitative measure of distances (frequency ratios) between the tones is therefore needed. For ETS with N semitones, M tones and interval structures n={n1,n2,...,nM}, where ni is the number of semitones between adjacent tones, the average distance between tones is N/2, independent of n. The variance σ(n) indicating the magnitude of fluctuations around the mean distance provides such a measure. Scales related by cyclical permutations and mirror imaging have the same variance. Complementary scales (e.g., major pentatonic) have their variances related, σ2(n)=|a|σ2(nC)+b, where a and b are constants independent of the scale structure, and variances of complementary scales behave in tandem. Thus the smaller the variance the greater is the distance among the tones. Increased fluctuations measure the amount of bunching. Numerical studies of variances agree closely with the results of the complexity analysis, namely that the major scale, the pentatonic scale and the modes have their tones placed as far apart from each other as possible.
Measurement and analysis of Byzantine chant frequencies and frequency intervals
Authors: Tsiappoutas Kyriakos , Ioup George E. , Ioup Juliette W.
Published: October 2013

A Byzantine music chant piece performed by a well-recognized chanter is used in order to measure experimentally the mean frequencies of the first five tones (D–A) of the Byzantine music diatonic scale. The experimental frequencies are compared with two traditional theoretical scales. It is found that a scale performed by a traditional chanter is very close to the frequencies of the proposed scales, except for tone F. The performer’s standard deviation from the mean frequencies for each tone is determined. The amount of deviation is not provided by theory. By comparison of these results to the notion of pitch discrimination from psychophysics, it is further established that the frequency differences are small not only physically (frequency), but also in terms of perception (pitch). The attraction effect (secondary tones are higher in frequency when found between a lower and a higher main tone and lower in frequency when between a higher and a lower main tone) is tested for all analyzed tones (D–A); it is found that the sole tone subject to the attraction effect is the only secondary tone (E). The frequencies characterizing the attraction effect have not been explained in theory and are quantified experimentally for the first time.
Constant interval distance between R1 and R2 of Spanish vowels sung at high pitch by sopranos
Authors: Castro-Sierra Eduardo , Zenker Miguel , Poblano Adrian , Ramirez-Trevino Alberto
Published: October 2013

Recently, Joliveau et al. [Nature 427, 116 (2004)] have studied the frequency distance between R1 resonance frequency and f0 of sopranos singing in English. Whereas at low-pitch singing this resonance frequency was roughly constant, at high-pitch singing R1 followed f0. This tendency held for vowels without lip rounding but not for those with lip rounding. Using CSRE45, at National School of Music of UNAM in Mexico City, R1 and R2 of the five tonic vowels (/a/, /e/, /i/, /o/, /u/) of Spanish words extracted from a traditional Mexican children’s song spoken or sung by 11 native-speaking sopranos with an average of 5 years of classical operatic training were analyzed. While speaking or singing at low or mid pitch, either resonance frequency fell within the distribution characteristic of each vowel, forming clusters. However, when singing at high pitch, there was a constant interval difference, irrespective of singer, between R1 and R2 of every vowel. Since it has a simple vowel system, and the frequency separations between formants of different vowels are relatively large, sopranos singing at high pitch in Spanish appear to easily maintain the interval difference between R1 and R2, and thereby the clarity of the vowels.
Experiences implementing ANSI S12.60 in classrooms
Authors: Herbert R. Kring , Erdreich John
Published: October 2013

Issues in meeting the ANSI 12.60 classroom acoustics standard fall into two categories: overcoming design team unwillingness to implement recommended criteria and finding practical methods of meeting issues of reverberation control and HVAC noise control. Solutions to HVAC noise control are emerging; an example is the use of fan coil units in new construction. Education of owners and designers is an ongoing process. It is hoped this paper contributes to a dialogue between the parties involved in school construction.
Case study of a prototype elementary school designed to meet the ansi classroom acoustics standard
Authors: Siebein Gary , Lilkendey Robert , Paek Hyun , Skorski Stephen
Published: October 2013

The school board standards group that prepares design criteria for a large district, an architectural firm specializing in educational environments, a contractor and an acoustical consultant formed a team to develop a series of bid alternates for a prototype elementary school to upgrade the acoustical performance of the school to meet the ANSI classroom acoustics standard. Three primary areas of work included room finishes to reduce reverberation times to 0.60 s or less; selecting wall assemblies and details to reach the STC 50 required in the standard to reduce sound transmission between rooms; and HVAC system design to reduce noise produced by the air-conditioning system to the 35 dBA required in the standard. Only minor adjustments had to be made to the finish materials and wall assemblies in the prototype school design to meet the requirements of the standard. Major changes in design concept and implementation had to be made to the HVAC system design to meet the 35 dBA requirement. The paper describes the prototype design, the design processes used to develop the modifications and the cost impacts of the proposed changes.
Acoustical renovation of portable classrooms for cochlear implanted pupils
Authors: Lubman David , Lopez Tim
Published: October 2013

Anticipating increased enrollment of children with cochlear implants, the Riverside County Office of Education undertook the acoustical renovation of two portable classrooms in California’s Riverside County: Wildomar Elementary School in Wildomar and Katherine Finchy Elementary School in Palm Springs. The aim was to improve the acoustical environment to make the classrooms suitable for pupils with severe hearing disabilities (reduce noise and reverberation). Lacking an acoustical standard specific for cochlear implanted pupils, the acoustical goals chosen were those of the ANSI acoustical standard S12.60-2002. Key changes were intended to reduce interior noise from HVAC and improve the facade insulation to reduce exterior noise intrusion. The resulting acoustical improvements are documented. Costs and lessons learned are discussed.
Classroom acoustics in a Leadership in Energy and Environmental Design (LEED) certified school
Authors: Doggett Felicia M.
Published: October 2013

Clearview Elementary School in Hanover, Pennsylvania, is the first school in that state to achieve LEED (Leadership in Energy and Environmental Design) certification. Additionally, it is only one of three K–12 schools nationwide to achieve certification at the Gold Level. A study of the classroom acoustics has been conducted in this school to evaluate how well a Gold Level LEED-certified building compares to criteria set forth in ANSI S12.60-2002. Also addressed is the success of implementing this standard in schools in the greater Philadelphia area and New Jersey, and the receptive attitude that architects in this region have for the standard. Both Philadelphia and the State of New Jersey are in the midst of a large effort to update old school facilities and build new ones.
A challenge to the Acoustical Society of America and its members to help accelerate adoption of the American National Standards Institute (ANSI) standard for classroom acoustics
Authors: Sutherland Louis , Lubman David , Erdreich John
Published: October 2013

The ANSI Standard on classroom acoustics, S12.60-2002, has the potential to greatly improve the quality and accessibility of public education. To realize its potential the standard must be put to use. The standard is now voluntary unless it is adopted by a state or school district or is incorporated into individual school construction bidding documents. In some parts of the US, the ANSI standard now gets consideration for construction of new or substantially upgraded schools. But wide scale adoption may take many years at the current rate of progress. To accelerate adoption of the ANSI standard in school construction a major effort is required to educate stakeholders. ASA and its members can play an important role in this endeavor by educating stakeholders, including architects, school building officials, and parent–teacher groups through workshops, seminars and other presentations. Consistent with ASA’s mission, to increase and diffuse the knowledge of acoustics and promote its practical application, ASA and its members can become ambassadors for good classroom acoustics in our communities. Some of the existing materials are described that can be used for this vital objective to help remove acoustical barriers to learning.
Range-depth tracking of humpback whales using autonomous acoustic recorders
Authors: Thode Aaron M. , Gerstoft Peter , Guerra Melania , Stokes Dale M. , Burgess William C. , Noad Michael J. , Cato Douglas H.
Published: October 2013

Matched-field processing (MFP) is a technique for tracking an acoustic source in range and depth by comparing the output of an ocean acoustic propagation model with measured acoustic data collected across multiple hydrophones [e.g., Thode et al., J. Acoust. Soc. Am. 107, 1286–1300 (2000)]. In October 2003 a MFP experiment was conducted using humpback whale sounds recorded during the spring migration off the Sunshine Coast in Queensland, in conjunction with a larger experiment conducted by the Humpback Acoustic Research Collaboration (HARC). Humpback whale sounds between 50 Hz to 1 kHz were recorded on a five-element vertical array deployed in 24-m-deep water. The vertical array consisted of a set of flash-memory autonomous recorders attached to rope with an anchor at one end, and a subsurface float at the other. Acoustic data were simultaneously collected and monitored on five sonobuoys deployed over approximately 2-km range. Using the range estimates from the sonobuoys as bounds on the matched-field processing, a geoacoustic inversion using the calls was performed on the vertical array data using a genetic algorithm. Preliminary results of the inversion and resultant 3-D position fixes are presented. [Work supported by ONR.]
A fast time-domain method for calculating the near field pressure generated by a pulsed circular piston
Authors: Kelly James , McGough Robert
Published: October 2013

A fast single-integral method has been derived for calculations of transient near field pressures generated by circular pistons. This new time-domain method outperforms other methods with respect to speed, accuracy, and ease of implementation. Unlike methods that apply the spatial impulse response, the new method inherently eliminates aliasing problems, which permits a significant reduction in the temporal sampling rate. As a result, the new method is approximately six times faster than the spatial impulse response for a 1% maximum numerical error. This new method converges exponentially with Gauss quadrature, whereas spatial impulse response methods evaluated with fast Fourier transforms only converge linearly with respect to sampling frequency. Thus, the new method achieves small numerical errors in very short times. Since the new fast method evaluates a single-integral expression that is readily computed with standard quadrature techniques, the implementation is greatly simplified relative to the spatial impulse response. The new method, which achieves smaller errors in less time with lower sampling rates, is also much more memory-efficient than the impulse response approach. Each of these advantages represents a significant improvement with respect to the impulse response method for computations of transient acoustic fields.
Experimental equalization of a one-dimensional sound field using energy density and a parametric equalizer
Authors: Shepherd Micah , Chen Xi , Leishman Timothy , Sommerfeldt Scott
Published: October 2013

A simple experimental method has been developed to equalize a one-dimensional sound field using acoustic energy density. Energy density is estimated using two methods: the two-microphone transfer-function method and the two-microphone finite-difference method. An equalization filter is manually configured for each using a digital parametric equalizer. The results of the two estimation approaches are compared. Equalization filters are similarly implemented for sound pressure measured at discrete points in the field and for spatially averaged sound pressure. Results of the approaches are compared and benefits of the energy density method are discussed.
Galilei experiments and common sense
Authors: Ayers R. Dean
Published: October 2013

Galileo Galilei showed us by example how to put hypotheses about the natural world to the test of scientific experiments. It is very likely that his attitude of healthy skepticism toward his own ideas and those of others was instilled in him by some work in musical acoustics. His father, Vincenzo (or Vincentio), was a prominent music theorist and composer as well as an accomplished lutenist. During his adolescence Galileo assisted Vincenzo in practical studies on the behavior of vibrating strings. That research examined the influence of various parameters on the pitch of a string (and hence its frequency), disproving some incorrect guesses. We are now in an age when many of our students are unduly influenced by popularized reports on exotic and seemingly bizarre open questions in relativity, cosmology, and elementary particles. That exposure encourages them to abandon their common sense and skepticism when they take a science course. Our specialty can provide a valuable counterexample by letting students perform exploratory, quantitative studies on the strings of the original Galilei experiments or on other vibratory systems. We can all benefit by remembering the lessons learned from such work. [Work supported in part by the Paul S. Veneklasen Research Foundation.]
The motion of harp strings
Authors: Waltham Chris
Published: October 2013

A harp is an instrument with a set of plucked strings that excite 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 motions of several small and large harps have been studied using small, fast 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 implications for the sound production are discussed.
Turbulence eddy viscosity in flutelike instruments
Authors: Bader Rolf
Published: October 2013

The generator area of a flutelike instrument is modeled by the finite-element-method (FEM) using a Navier–Stokes (NS) model and a k-epsilon turbulence model. A steady-state simulation with condition of zero pressure at the tube’s end and a transient simulation using a back-impulse from the tube’s end to the generator area was performed. Both models NS and k-epsilon agreed in the overall structure of the volume flow from the player’s lips split in a part flowing into the tube and one flowing outside, common in eddy and vortex structure. But the k-epsilon model showed a much more realistic description of the relation of flows into and outside the tube. As the NS model results in a one-to-one split of the flow, the turbulence model leads to a much smaller flow part into the tube with most of the flow going outside and so to a much higher vorticity at the flute lip. The transient model also shows a sharpening of the transient pressure curve because of this sharpened lip near vorticity behavior. So as the turbulence model seems to be a good choice in formulating a discrete flute model, the overall eddy damping seems to play an important role in flute dynamics.
Separation of musical instrument timbre using performance information and real-time harmonic/inharmonic component filtering
Authors: Sarlo Joseph A.
Published: October 2013

Described here is a technique for the real-time separation of a musical instrument timbre from a multitimbre sound source. The separated timbre may be a timbral component of a single musical instrument timbre (e.g., the breath noise from a wind instrument) or an instrument timbre from a multi-instrument sound source. The separation is accomplished by first using performance information, such as pitch tracking or score alignment, to estimate a fundamental frequency for the source of the timbre to be separated. Real-time analysis/resynthesis filtering of the sinusoidal components based on their harmonic relationship to the estimated fundamental frequency is then employed to extract the desired timbre.
Synthesis of audio spectra using a diffraction model
Authors: Vijayakumar V. , Eswaran C.
Published: October 2013

It is shown in this paper that the intensity variations of an audio signal in the frequency domain can be explained by using a Fresnel diffraction model. By proper choice of two parameters an input spectrum of discrete frequencies of unit intensity can thus be transformed into the known spectra of different musical instruments. Specific examples of musical instruments are considered for evaluating the performance of this method. It is found that this model yields musical spectra with a good degree of accuracy. Synthesized sounds of bells and drums are presented as real examples.
Design and performance of hybrid feedforward-feedback active noise reduction for hearing protection and communication
Authors: Ray Laura
Published: October 2013

Since the 1990s research and development of digital feedforward active noise reduction (ANR) based on least-mean-square (LMS) algorithms has shown that significant gains in noise reduction can be achieved for circumaural hearing protectors. However, to-date digital feedforward hearing protection devices have not penetrated the market. This presentation reviews prior research in feedforward ANR for circumaural devices, along with the opportunities and challenges for commercialization of the technology. The effect of noise source characteristics, specifically stationarity and dynamic range, on stability and performance of LMS filters is examined. Research on hybrid ANR architectures combining LMS filters and digital feedback ANR is reviewed, showing that robust performance with stability margins required for a commercial product can be achieved with such systems. The role of ANR in enhancing speech intelligibility is outlined, along with research needed to develop standards for measurement of stability, ANR performance, and speech intelligibility afforded by digital feedforward ANR devices. The paper concludes with a presentation of opportunities offered by feedforward ANR in intra-aural and supra-aural hearing protection devices.
Development and performance of an active noise reduction earplug for use in extreme noise environments
Authors: McKinley Richard L. , Hall John Allan , Saunders Will , Vaudrey Mike
Published: October 2013

High-performance military fighter aircraft at high power settings can generate near-field noise levels typically between 140 and 150 dB SPL at approximately 50 ft. Providing adequate noise attenuation for maintenance personnel working in these locations is a challenging task. This paper describes the basic design of an active noise reduction earplug that, when combined with a passive earmuff, will operate in noise environments up to 150 dB SPL. The design and fabrication was the result of a contractual collaborative effort of the Air Force Research Laboratory and Adaptive Technologies Inc. The basic design includes a custom-molded deep insert earplug with an integrated error microphone and earphone. The active noise reduction controller was realized using digital signal processing. The performance of the ANR earplug and earmuff system was measured in both laboratory and field conditions using both real-ear attenuation at threshold and miniature microphone in real-ear measurement techniques. The performance of the system will be described in terms of both active and passive attenuation in 142–150-dB SPL broadband noise fields.
Manipulation of cells in ultrasound standing waves
Authors: Coakley W. Terence
Published: October 2013

The acoustic radiation force operating on a cell in a 0.5-MPa pressure amplitude 3-MHz standing wave field equals that experienced in a 250-g gravitational field. Consequently, cells may be driven rapidly to preferred points in the sound field. Acoustic radiation pressure can drive bacteria, flowing by an acoustic reflector (prepared as an immunosensor surface), onto that surface where they are then captured. Animal cells have been driven onto the fabric of wide-gauge filters to form, a basis for a supported bioreactor. Real standing wave fields do not have the ideal plane-wave form, particularly when the transducer diameter is much larger than a wavelength (typical transducer diameter of 20 mm, wavelength of 0.5 mm at 3 MHz in water). Pressure variations within a node plane then give rise to regions towards which cells migrate and may be held against flow in potential traps. These traps are exploited commercially to retain cells in fermentors in the pharmaceutical industry. Most recently, ultrasound traps have been employed to concentrate animal cells in the focal plane of a fluorescence microscope so that cell interactions and their consequences at the molecular level can be monitored.