bluuebunny/crossref_metadata_2025 huggingface dataset:
Some acoustics of the shakuhachi—and of the shakuhachi player’s face
Authors: Wolfe Joe , Smith John
Published: July 2012

The shakuhachi is an end-blown Japanese flute. Like other flutes, it is open at the place of excitation, so it operates at minima of the acoustic impedance. The jet interacts with both the bore impedance and the radiation impedance, which is baffled by the player’s face. Large changes in the relative geometry of the instrument and the face contribute to the flexibility in pitch and timbre that are important elements of the traditional playing style, and which gives the instrument much of the expressiveness for which it is renowned. We report measurements of the impedance spectra Z(f) of the bore, and of the baffled radiation load imposed on the jet. Z(f) of the instrument differs from that of the Western flute family because the shakuhachi has neither the narrow chimney of the Western flute, nor the short resonator upstream of the jet. These influence the overall form of Z(f) for the instrument. Other features of Z(f) are explained by the tone hole position and geometry. The Z(f) of the radiation field varies for different playing positions, which has important effects on the tuning of the minima and on the spectral response.
Alvin M. Liberman and the development of Midwestern speech scientists
Authors: Jenkins James J.
Published: July 2012

In the summer of 1968, Alvin Liberman came to the University of Minnesota to teach a special seminar in speech perception for the Center for Research in Human Learning. His efforts with the gifted students of the Center not only produced a piece of original research on the perception of speech, but also initiated a productive relationship between the University and Haskins Laboratories. Faculty and students from three different academic departments trekked back to New Haven to make stimuli and profit from the intensely interacting pattern of collaborative work at Haskins Laboratories. This largess was possible because of the special relationship between Haskins and NICHD that supported our use of the Haskins facilities. This relationship was typical of Al’s outreach to interested scientists everywhere. At the University of Minnesota alone, over the next decade the relationship produced numerous masters theses and doctoral dissertations. More importantly, it facilitated the training and development of almost a dozen speech scientists who are continuing to advance the field of research to which Al devoted his professional life.
Functional role of efferent feedback to the inner ear
Authors: Liberman M. Charles
Published: July 2012

With Alvin Liberman as a father, a career in scientific research was the only one I seriously considered. However, I did stray as far as the study of hearing rather than speech. One of the major interests of my laboratory is the functional role of the neuronal system of efferent feedback to the inner ear, known as the olivocochlear pathway. One part of this olivocochlear pathway projects to the outer hair cells and constitutes a sound-evoked reflex which, when activated, reduces the sensitivity of the cochlea and raises thresholds to sound. In a series of neurophysiological studies in cat and guinea pig, we have shown that, paradoxically, this efferent feedback can act to improve the detection of transient signals in steady background noise and that the presence of an intact efferent pathway also protects the ear from acoustic injury due to overly intense sound.
Alvin M. Liberman’s legacy: Haskins Laboratories
Authors: Whalen D. H.
Published: July 2012

Alvin M. Liberman came to Haskins Laboratories in June 1944 to help create a reading machine for the blind. Under Franklin S. Cooper, his group did create the first such system but, more importantly, Liberman led the way in creating an environment where the basic issues of speech and reading could be addressed by an assemblage of specialists which could not reasonably be supported by any one academic institution. The technological tools that were first available only at Haskins—controlled speech synthesis on the Pattern Playback, EMG recording, and dichotic presentation in particular—were the primary attractors, but the collaborations continued long after the equipment became less than unique. Haskins embodied the scientific ideal of the free exchange of information, across disciplinary boundaries, to a greater extent than most other institutions. A large force behind it all was Liberman’s insistence on the highest technical expertise backing up theoretically interesting experiments. He was rightfully proud of the fact that Haskins results always replicated, whether the interpretation was accepted or not. The atmosphere of scientific rigor continues at Haskins, and will remain so as long as we can continue to uphold the high standards that Liberman set for us.
Ultrasonic fault detection by processing of signals from fixed transceiver system
Authors: Mahmud Khan Mohammad , Ohba Ryoji
Published: July 2012

A nonscanning method for an ultrasonic flaw detection technique is described. The system employs an M-sequence modulated ultrasonic wave as the excitation signal. Irrespective of the number of faults to be detected, the data acquisition system predeterminedly consists of a transmitter and a few receivers to be fixed at convenient locations. The cross-correlation function (CCF) between the original M-sequence and the demodulated received sequence indicates the presence of faults in the form of sharp peaks. In order to clearly detect the expected peaks corresponding to the faults in the CCF, new signal processing techniques are proposed. Experimental results (on metal plate) demonstrate the capability of the system and confirm the feasibility of the approach under heavy ambient noise condition. An algorithm, only on the basis of travel time of the signal, to determine the exact location of a fault is described. Synchronous moving average and coincidence multiplication process are found to be very effective in eliminating the false peaks from the CCF while increasing the SNR significantly. The former can be easily modified for the purpose of next generation online signal processing of an ultrasonic NDT signal. [The authors would like to express their gratitude to the Ministry of Education, Japan, for support with the scholarship as well as the funds needed for this research.]
On the use of the sonar equation approximation when computing the response of a target in shallow water
Authors: Sarkissian Angie , Dragonette Louis R.
Published: July 2012

The sonar equation may be used to compute the scattering response of a target in shallow water by approximating the target to be a point scatterer. The approximation significantly simplifies the interaction of the scatterer with the medium. In the more general case, since the field produced by a source arrives at the scatterer through multipaths, it is incident on the target at various directions. The response of the scatterer must be computed at all of the incident angles to obtain the correct scattered field in shallow water. Scattering results computed using the sonar equation are compared to the more correct solution for a ribbed cylindrical shell placed in shallow water for various monostatic and bistatic geometries to examine the validity of the use of the sonar equation at various frequencies and geometries. [Work supported by ONR.]
Monte Carlo model for underwater ambient noise fields
Authors: Hutt Daniel L. , Rosenfeld Andrew L. , Hines Paul C.
Published: July 2012

Three-dimensional ambient noise fields possessing realistic cross-spectral properties have been simulated using the Monte Carlo method. In the model, weighted monochromatic sources are distributed about an array of sensors to create the desired directional characteristics of the noise field. The hydrophones can be positioned arbitrarily to form any desired array structure and orientation. Noise signals are represented in the frequency domain where phase shifts due to propagation are most naturally applied. Examples of simulated cross spectra for a variety of noise fields will be presented. Good agreement with theory is found for cases in which analytical solutions are possible.
Amphitheater noise, a community perspective
Authors: Blomberg Leslie D.
Published: July 2012

Amphitheaters and amplified music often provoke strong community reaction. Leaders of approximately 20 community organizations near existing or proposed amphitheaters were surveyed, and three were selected for case studies. Their experience provides insight into the affected public’s perception of the concert industry, acoustical consultants, ordinances, and regulations.
Practical considerations for the design and construction of an acoustic dynamometer
Authors: Smith Robert W. M. , Heake John F. , Garrett Steven L.
Published: July 2012

An instrumented, variable acoustic load of the type described by Fusco [Fusco et al., J. Acoust. Soc. Am. 91(4), 2229–2235 (1992)] and Gardner [D. L. Gardner and G. W. Swift, Cryogenics 37(2), 117–121 (1997)] has been implemented for the testing of high power (greater than 1.5 kW) electrodynamic loudspeakers for thermoacoustic refrigerator applications. The load serves to facilitate performance measurements for these loudspeakers under various operating conditions, a role analogous to a dynamometer in conventional rotating machinery. Attached to a primary acoustic resonator, the acoustic dynamometer consists of a 2-in angle globe valve and other flow constrictions connected to an acoustic compliance. The design of these flow restrictions employed the acoustic ‘‘minor loss’’ model developed by Swift et al. [Swift et al., J. Acoust. Soc. Am. 105, 711–723 (1999)]. Measurements of the dynamometer performance agreed with the calculated acoustic impedance to within 16%. At powers exceeding 1 kW, agreement between the acoustic load dissipation and other measurements of loudspeaker power agree to within 3%. To illustrate the utility of an acoustic dynamometer, a brief summary of measurements on two moving-magnet loudspeakers will be presented. [Work supported by ONR.]
Effects of basilar membrane roughness and nonlinearity on stimulus frequency otoacoustic emissions
Authors: Talmadge Carrick L. , Tubis Arnold
Published: July 2012

Stimulus frequency otoacoustic emissions (SFOAEs) may be evoked via basilar membrane (BM) nonlinearity, BM roughness (random inhomogeneities), or a combination of these properties. Emissions generated by BM nonlinearity alone have phase gradients that are too small to account for the observed emission fine structure [e.g., Shera and Guinan (1999)]. Linear reflection via BM roughness can account for the main phase characteristics of the emissions [e.g., Shera and Zweig (1993); Talmadge et al. (1995)]. It is shown theoretically that, contrary to what is expected from naive considerations concerning phase derivatives and group delays, the physical time delays associated with both emission mechanisms are approximately equal to the round-trip cochlear wave travel time from the cochlear base to the tonotopic place for the stimulus frequency. A theoretical framework is presented for describing the combined effects of roughness and nonlinearity on the emission fine structure. For the case of cochlear roughness and a weak nonlinearity, it is shown that in some instances, the nonlinearity can significantly modify the level and phase behaviors of the fine structure and actually enhance the fine structure patterns. The implications of these results for the stimulus level dependence of SFOAE fine structure are also explored.
Objective discrimination of extensity: Concurrent versus successive sound sources
Authors: Tirtabudi Prisilia , Perrott David
Published: July 2012

This study compared human ability in processing and detecting concurrent versus successive sound stimuli and the degrees of angular separation between sources. Bursts of broadband white noise at 85 dB (SPL) were presented with duration of either 1000, 300, 100, 30, or 10 ms. Angles between speakers for each duration time were at 4.5°, 9.0°, 18°, 27°, and 36°. Two pairs of bursts were presented at a time, either simultaneously or sequentially. Participants were to discriminate whether the first pair of bursts had a larger angular separation between sources than the second pair. Listeners’ performance were almost similar between concurrent versus successive stimuli when the durations were 1000, 300, and 100 ms. However, as the duration of the stimuli dropped to 30 and 10 ms, so did the performance in the concurrent condition. In addition, as the angles between the two speakers grew farther apart in both conditions, the degrees of jnd (MAA) were also increasing. Results will be discussed in terms of the auditory system’s ability to resolve spatially distributed sources that are set off either concurrently or sequentially.
Listeners in Sweden perceive tritone stimuli in a manner different from that of Americans and similar to that of British listeners
Authors: Chalikia Magdalene H. , Leinfelt Fredrik
Published: July 2012

The tritone stimuli consist of two tones, each of which has octave-related harmonics. The two tones are separated from each other by a half-octave (a tritone interval). The tones are typically presented successively, and listeners decide whether or not the second tone in the pair is perceived as ascending or descending, relative to the first one. Responses tend to vary across listeners for the same stimuli, and for different stimuli. In this study, participants from Stockholm, Sweden, were presented with such tritone pairs and were asked to determine if they heard each pair as ascending or descending. Deutsch’s (1991) hypothesis, that language background may influence the perception of the tritone stimuli, was tested. All participants were speakers of both English and Swedish. Their data were compared to data of English monolinguals tested in Texas, and California, as well as listeners from the south of England. Preliminary results suggest that the overall perception pattern in Sweden differs from that found in Texas and California, but tends to be similar to the perception pattern found with English listeners.
Monitoring and localizing simultaneous real-world sounds: Implications for the design of spatial audio displays
Authors: Guettler Diane L. , Bolia Robert S. , Nelson W. Todd
Published: July 2012

Numerous researchers have investigated the extent to which human listeners are able to localize free-field and virtual acoustic stimuli. Despite the abundance of this research, few studies have focused on the number of sounds a listener is able to localize simultaneously, and even fewer have employed naturally occurring or real-world sounds. Results from these types of experiments may have important implications at the basic research level within the fields of perception and attention, and may also prove useful for guiding the design of spatial audio displays in applied disciplines such as engineering and human factors. In the present study, listeners localized between one and three virtual acoustic stimuli, the positions of which were restricted to the horizontal plane under factorial combinations of seven spatial locations, three set sizes (one, two, or three sources), and three distinct acoustical sounds of a real-world nature (e.g., a crying baby). The paradigm employed required participants to monitor a set of simultaneously presented sounds and localize one specific sound when prompted. Performance was measured in terms of average localization error and percentages of front–back confusions. These results will be discussed in terms of their implication for the design of spatial audio interfaces for complex, multitask environments.
Backscattering by tilted cylindrical shells above the coincidence frequency caused by helical flexural waves
Authors: Blonigen Florian J. , Marston Philip L.
Published: July 2012

Generalized leaky Lamb waves excited by ultrasound incident on cylindrical shells in water produce important backscattering effects. At a certain critical tilt angle, leaky waves launched along the meridian of the cylinder have been shown to lead to large backscattering enhancements [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)]. At angles less than the critical tilt, these leaky waves follow helical paths and also make significant contributions. In the present work, experiments using tone bursts were performed on a stainless steel shell to investigate the contributions of a0 leaky Lamb modes. The tone bursts were of sufficient duration to superpose helical wave bursts of successive circumnavigations, along with the meridional contribution near the critical tilt, to arrive at a steady state backscattering amplitude for the cylinder. This was compared against an approximate numerical partial wave series solution and a ray theory solution as a function of the tilt angle. The data follow the basic shape of the theoretical curves. However, the experimental amplitudes are more suppressed at higher frequencies resulting from losses due to reflection of leaky waves at the cylinder’s end. [Work supported by the Office of Naval Research.]
Intelligibility of aircraft loudspeakers
Authors: Warnaka Glenn E. , Warnaka Mark E. , Mapp Peter , Shimizu Bruce
Published: July 2012

Commercial aircraft audio systems provide audible messages including greetings, details of the flight, comments on entertainment, and important safety information. Hence, the speech intelligibility of aircraft audio systems is of great importance. Distributed-mode loudspeakers (DMLs) are known to have wider sound dispersion, especially at higher frequencies, than conventional cone loudspeakers. As aircraft loudspeakers are located relatively close to the passengers, the narrower dispersion and beaming of the high frequencies from conventional cone loudspeakers can cause loss of intelligibility for passengers not on the axis of the loudspeaker and produce uneven sound distribution within the cabin. DMLs have demonstrated intelligibility superior to conventional loudspeakers in other applications such as public address systems. DMLs have other advantages in aircraft installations. They are very lightweight and can even be built into the internal trim, resulting in a nearly zero-weight loudspeaker. Their essentially flat configuration also requires less volume. This paper presents a comparative evaluation of the speech intelligibility of current aircraft loudspeakers and DMLs as determined by the STI (Speech Transmission Index) using the RASTI (Rapid Speech Transmission Index) method in accordance with RTCA document DO-214. Tests were performed under representative conditions and for different seating arrangements.
Time-dependent signal representations that are independent of sensor calibration
Authors: Levin David N.
Published: July 2012

Suppose that the sensor arrays of two speech recognition systems, Sx and Sy, are calibrated differently so that they have different responses (x and y) to the same sound. It is difficult for pattern recognition software to handle such variable sensory data. This paper shows how to avoid this problem: each device transforms its sensory data elicited by an evolving sound into the same ‘‘canonical’’ representation so that it is suitable for analysis by pattern recognition algorithms. Assume that the two systems have previously been exposed to samples of the same collection of sounds. These ‘‘training’’ data induce an affine-connected differential geometry on the sound manifold, which the two sensor arrays represent in different coordinate systems (x and y). Without communicating, the two systems can utilize this geometry to construct the same coordinate-independent (scalar) representation of any time-dependent sound of interest. This methodology is demonstrated by applying it to simulated data from devices with two sensory channels (e.g., for measuring the frequency and amplitude of tones). This approach mimics human perception, which also tends to be constant across systems (individuals) with different sensory distortions, as long as they have been exposed to similar collections of stimuli in the past.
Crime-detection speaker recognition system
Authors: Gorban Igor I. , Magera Vitalij N. , Levij Sergey V.
Published: July 2012

Crime-detection automatic speaker verification and identification (CASVI) system oriented to nonprofessional experts was described at the 137th ASA Meeting [I. I. Gorban, N. I. Gorban, and A. V. Klimenko, J. Acoust. Soc. Am. 105, 1353 (1999)]. At the current meeting another speaker recognition system for professional crime-detection experts is presented. It consist of special units, Pentium-type computer, and programs realized speech-processing algorithms in automated and automatic modes. The system gives the possibility to research records made on different tape recorders, to fit tape speed, to decode speech records, to suppress noises, to correct frequency and nonline record distortions, to sort sounds, to measure and calculate different discriminate features, characteristics, and parameters usually used by crime-detection experts in their practical work, to compare the records, to form libraries and archives, and to make reports. The system has a simple and comfortable interface tailor-made for crime-detection expert aims. Police exploiting of the system has shown that utilization of the system raises productivity of expert work sometimes and essentially improves authenticity of phonoscope expertise.
A machine learning technique for evaluating cues to stop place
Authors: Plauche’ Madelaine C.
Published: July 2012

This paper is situated in a long line of phonetic studies that seek to determine and qualify the acoustic cues humans use to identify stop place. Acoustic information relevant to the identification of stop place resides in the relative amplitude (Cooper et al., 1952; Ohde et al., 1983) and spectral characteristics of the burst (Blumstein et al., 1979; Stevens, 1999), as well as in formant transitions (Dorman et al., 1996) and voice onset time (Klatt, 1975). Consonant confusion studies suggest that vocalic context is an important factor in the perception of neighboring stops. In the environment of a high front vowel (/i/), for example, cues such as formant transitions and VOT may be neutralized, resulting in a dependence on transient features that are secondary cues in other contexts (Plauche’ et al., 1997). The present study estimates the effect of vocalic context on the relative ranking of acoustic cues for stops in CV sequences using a machine learning algorithm (decision trees) that evaluates a database of 1500 (English) CV tokens and their values for the acoustic features: (1) VOT, (2) energy and power of the burst and release, (3) spectrum at the burst, and (4) formant transitions into the following vowel.
Measurement-based geoacoustic modeling for the Acoustic Characterization Test III
Authors: Rozenfeld Ilya , Siegmann William , Carey William , Cable Peter
Published: July 2012

The Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea to provide accurate measurements of sound transmission and coherence (array signal gain) under known environmental conditions. Bottom sampling and sub-bottom surveys, coupled with archival geophysical information, provided the basis for geoacoustic profiles of sound speed, density, and attenuation versus depth. These profiles and the measured bathymetry and water sound speed were used as input parameters for parabolic equations computations. Very good agreement was obtained between measured and calculated narrow-band transmission loss by employing slightly modified geoacoustic profiles and an attenuation profile with a near-water-sediment interface power-law frequency dependence of 1.8. This power law was determined through the use of an effective attenuation coefficient and a least-square analysis of transmissions from five narrow-band tones between 47 and 604 Hz. These results are consistent with measurements in other sandy–silty areas. Using these parameters, comparisons were made between independent measurements and calculations of broadband transmissions and of signal spread, and excellent agreement was found. [Work supported by ONR.]
Anomalous signal loss in the Yellow Sea, revisited: Coupling the acoustics with model-generated oceanographic realizations
Authors: Chin-Bing Stanley A. , King David B. , Warn-Varnas Alex C. , Zingarelli Robert A. , Lamb Kevin G.
Published: July 2012

In a seminal paper, Zhou et al. [J. Acoust. Soc. Am. 90, 2042–2054 (1991)] introduced the concept of large anomalous signal loss due to a resonance effect caused by solitons (internal waves traveling along the thermocline). They assumed that solitons were present and produced a remarkable comparison between acoustic model predictions and their acoustic measurements taken over a four-year period. They did not take sufficient oceanographic measurements to confirm the existence of solitons. Numerous investigators have tried to duplicate their pioneering work in similar shallow-water environments with solitons present. Signal reduction, mode conversions, and resonance-like effects have been observed, but signal loss of the magnitude measured by Zhou et al. have not been observed. We have used a primitive equation soliton model and the tidal flow near the Shandong peninsula to generate soliton simulations that flow into the Yellow Sea near the region where Zhou et al. made their acoustic measurements. We are performing analysis similar to that of Zhou et al. on these soliton realizations to determine if large signal losses can occur. Results from this investigation will be presented and discussed. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]
Broadband acoustic variability due to internal solitary waves
Authors: Mu Yongke , Badiey Mohsen , Lynch James F. , Wolf Stephen N. , Siegmann William L.
Published: July 2012

A shallow water (70–90-meter-deep) broadband acoustic experiment with a source-receiver range of 15–18 km in an azimuthally dependent environment was designed as a part of the SWARM’95 field study. Temporal behavior of the water column was sampled every minute from two sources placed above and below the thermocline transmitting signals over a period of several hours while the water column was measured for the passage of internal waves. Spatial behavior was sampled in the vertical plane by hydrophones with spacing on the order of meters. Coherence of broadband acoustic waves for frequencies (20–300 Hz) is examined for the waveguide over different environmental conditions. The effect of environmental variability on coherence, in particular the sound-speed fluctuations in the water column due to the internal solitary waves, is noted as a function of acoustic frequency and azimuth. Analysis of the acoustic fluctuations over short time scales (10–15 minutes) may resolve the temporal decorrelation of the received signal due to internal waves. The vertical sampling of the received signal permits an analysis of arrival-angle fluctuations. Numerical simulations are performed, which provide support to the experimental observations. [Work supported by ONR.]
Creativity in theme park acoustics
Authors: Long Marshall
Published: July 2012

Theme parks are places where the entire environment is a theater in which the guests are active participants. As such it emphasizes creativity of concept and design, including acoustical design. Creative solutions have been found for acoustical problems including innovative uses of materials, mechanical and sound systems. A number of examples are presented from the author’s 20-year experience with theme park acoustics illustrating examples of creative use of scientific principles.
The impact of propagation anomalies on noise emissions from entertainment facilities
Authors: Bronsdon Robert
Published: July 2012

Most measurements made on environmental noise sources are done whenever it is convenient without any real consideration to the effects of environmental factors such as wind and temperature gradients. Predictions are typically done assuming that the atmospheric conditions are stable and benign. When the predictions and test results are compared and do not match, a generalization is given: ‘‘It must have been caused by some type of atmospheric condition.’’ A computational Gaussian beam program that accounts for the effects of wind and temperature inversions was presented at Inter-noise 98 in New Zealand and is now currently a part of the SoundPLAN program for evaluating environmental noise. That program is designed primarily to deal with temperature inversions and wind that is blowing from the source to the receiver, but it does provide insight into upwind propagation. This paper explains how upwind propagation of sound in temperature inversion conditions can impact noise receivers in urban settings.
Animal sound analysis and playback software: Building a software tool useful to field researchers
Authors: Burt John M.
Published: July 2012

Many researchers would like to conduct sound-playback experiments with the level of control potentially available using a computer, and yet there are few programs specifically designed for computer-based playback. The lack of PC playback software led to the development of a windows 98 application called syrinx, which is specifically designed for both sound analysis and playback in the field. The goal was to provide a host of playback features that would allow researchers to conduct sophisticated field playback experiments using a sound card-equipped laptop PC and a portable speaker. syrinx can display multiple sound files as playable spectrograms, has a small suite of tools for editing sounds, displays a real-time scrolling spectrogram of audio input, allows users to log behavioral events, and has a number of other features useful for playback research. The talk will focus on the field-research-driven design goals for the syrinx project, how the program was implemented, what signal-processing tools and features were thought to be necessary for field researchers, what new features may be implemented in the future, and the challenges involved in developing a researcher- and field-friendly playback program.
Estimation of subsurface ocean density structure using remote sensing and data assimilation
Authors: Bobanovic Josko , Thompson Keith
Published: July 2012

Recently, researchers from Dalhousie University, The Royal Military College, and the Defence Research Establishment Atlantic started work on estimating water density, and eventually underwater acoustical properties, from in situ and remotely sensed data. This requires the development of assimilation schemes to project vertically into the ocean interior the surface information gathered by remote sensing. Initially, we are concentrating on inferring the seasonal distributions of temperature and salinity on the continental shelf. We are experimenting with new ways of assimilating such data into fully nonlinear, baroclinic models using the incremental approach. In a nutshell, the approach uses two parallel ocean models: a complex model to be fit to the data, and a simple model with known adjoint that is used to correct the control variables of the complex model. The result is a set of seasonal fields that is consistent with the observed data, and dynamical constraints imposed by the model, within prescribed errors bars. Our long-term objective is to develop practical schemes for assimilating time sequences of remotely sensed (e.g., SST, ocean color, altimetry, HF radar) data into any ocean model. Progress will be reviewed.
MEANS: Multiscale environmental assessment network studies
Authors: Schmidt Henrik , Robinson Allan , Kantha Lakshmi , Sellschopp Jurgen
Published: July 2012

The small-scale coastal acoustic environment is extremely difficult to predict and forecast. The very shallow near-shore region, with water depths of up to a few tens of meters, is particularly challenging due to the variability of the critical seabed properties due to sediment transport processes, biological processes, and changes in small-scale bathymetry due to wave action, with strong implications for the high-frequency reverberation characteristics in particular. The potential of using small autonomous underwater vehicles (AUV) with high dependency on acoustic systems in such environments has led to an increased need for forecasting the acoustic characteristics. The coastal ocean environment is a result of a very complex dynamical system with strong coupling among different scales. To investigate the predictability of this process, the MEANS effort implements a nested forecasting framework for the small-scale oceanography in Procchio Bay, Elba during the GOATS’2000 AUV technology experiment in Sep.–Oct. 2000. A local high-resolution model is constrained by assimilating oceanographic data from AUVs and moorings, and nested within a regional Ligurian Sea model and a basin scale circulation model, both constrained by surface ship measurements and satellite remote sensing data. The nested observation and modeling framework will be described, and preliminary results will be presented and discussed. [Work supported by ONR and SACLANT.]
Gas turbine noise mitigation for a residential development
Authors: Buntin Jim
Published: July 2012

A residential development was proposed adjacent to a gas turbine electrical power production peaking facility. To determine compliance with local standards, noise levels and frequency content were measured at reference locations under summer and winter conditions. The Environ. Noise Model (ENM) was calibrated on the basis of the reference noise level data, and noise measurement results at other locations were compared to the ENM predictions. The measurement results were also used to determine the effective noise source height for calculations of shielding. The ENM was then used to predict noise levels at the development site. To evaluate methods of obtaining compliance with the standards, the ENM was used to assess the effects of berms, walls, and grading on the development site, and an enclosure for the gas turbines. Recommendations were then prepared for noise abatement and mitigation measures, including the use of an enclosure, an onsite berm, and reduction of low frequency noise.
Computational investigation of wave steepening in a two-dimensional duct
Authors: Erskine W. R. , Selamet A. , Radavich P. M.
Published: July 2012

The need for accurate modeling of nonlinear phenomena, such as wave steepening, in unsteady flows is important in many engineering applications. Wave steepening causes the initial sinusoidal shape of the oscillation to distort and eventually form a shock wave. Both pressure and velocity waves steepen as flow moves downstream inside a duct. A computational fluid dynamics code, which solves the compressible, unsteady, two-dimensional Navier–Stokes equations, is used to investigate this nonlinear behavior and predict the flow field in a long narrow duct. A sinusoidal inlet velocity and an anechoic termination outlet are imposed as boundary conditions. The shape and frequency content of the traveling wave are predicted at various locations inside the duct. Inlet velocity is varied to cover a range of small-to-large amplitude pressure fluctuations. Results indicate that wave steepening is enhanced as the wave travels downstream and/or as the fluctuation amplitude increases. At large enough amplitudes and/or duct lengths, a shock is produced which travels to the outlet. Regardless of the oscillation frequency of the inlet velocity, the frequency spectra reveal sound-pressure level amplitude peaks at multiples of both quarter- and half-wavelength resonances based on the length of the duct.
Fast acoustic power computations for structural optimization problems
Authors: Fahnline John B.
Published: July 2012

Boundary element analyses in acoustics are often computationally inefficient because a large complex-valued matrix has to be solved at every frequency for which a solution is desired. This problem can be alleviated somewhat by using appropriate mesh densities for both the structural acoustic analyses, as discussed previously by the author. To achieve further enhancements, a computer program has been written to interpolate the acoustic resistance matrix over a frequency band from values calculated at sparse intervals. A preliminary analysis is performed to map out the resistance matrix as a function of frequency, requiring specification of only the frequency band of interest and the desired error tolerance. Automatic refinement is performed in regions where the resistance varies rapidly, as it does near acoustic resonances. A simple interpolation scheme is then used to compute the resistance matrix at any arbitrary frequency knowing the precomputed matrices, resulting in an order of magnitude reduction in the computation times when compared to a direct calculation. Because the acoustic analysis is independent of structural parameters, this formulation is ideal for problems where structural parameters are to be optimized without changing the radiating surface’s shape. Examples are given to demonstrate the formulation’s accuracy and computational efficiency.
Lagging application with use of sound intensity
Authors: Monh Sokcheat
Published: July 2012

Improvements were proposed to an existing county waste water sump station. The improvements included installation of a scrubber unit used to filter odor from the sump chambers. Noise from the operation of the scrubber unit raised concerns among nearby residents. To address compliance with local standards and minimize impacts on nearby homes, sound intensity testing was used to determine which modules of the scrubber unit made significant contribution to the overall noise levels. Lagging was recommended, and it was implemented by the county. Before and after sound intensity levels of the scrubber unit demonstrated the effectiveness of lagging as a mitigation measure.
The multiple source feedback of supersonic jet screech, I: Theory—frequency
Authors: Powell Alan
Published: July 2012

Screech sound, generated by the interaction of jet instability waves with the spatially periodic cell structure of choked or ‘‘off-design’’ supersonic jets, feeds back to initiate new instability waves at the nozzle. The interaction produces a phased array of effective point sources distance s apart, with a single equivalent (centroidal) source at distance n′s from the nozzle. The feedback criteria discussed at the last Meeting yield frequency f=fPRφ, where fPR=(U/s)⋅1/(1+M) for perfect reinforcement at the nozzle; U,M=instability wave velocity, Mach number; φ=(N+p+ν+I)/n′→1 with n′s≡(N+μ+ν)s, νs=distance of equivalent source from nearest cell end at (N+μ)s from the nozzle, N=integer, |μ|≤1/2, and I=−1, 0, or +1. Exact for any number of symmetrically disposed source strengths, numerical solutions show it to be a good approximation for arbitrary strengths and for inclusion of differing source distances (with weighted equivalent source). The mean s is appropriate for unequal source spacing; but then perfect reinforcement cannot occur. With perfect reinforcement unlikely, the 1953 hypothesis that f→fPR is confirmed as a simple and useful approximation.
Hydrodynamic lift and drag fluctuations of a sphere—theoretical model
Authors: Howe M. S. , Lauchle G. C. , Wang J.
Published: July 2012

A theoretical investigation is made of the unsteady lift and drag exerted on a sphere in a nominally steady high Reynolds number, incompressible flow. The net force on the sphere has previously been ascribed to fluctuations in the bound vorticity in the meridian plane normal to the force, produced by large-scale coherent structures shed into the wake. A simplified model of vortex shedding is proposed that involves coherent eddies in the form of a succession of randomly oriented vortex rings, interconnected by pairs of oppositely rotating line vortices, and shed at quasiregular intervals with a Strouhal number ∼0.19. The rings are rapidly dissipated by turbulence diffusion, but it is shown that only the nascent vortex ring makes a significant contribution to the surface force, and that the force spectrum at Strouhal numbers exceeding unity is effectively independent of the shape of the fully formed vortex. Predictions of the lift and drag spectra at these frequencies are found to be in good accord with new towing tank measurements performed on a neutrally buoyant sphere configured as an acoustic velocity hydrophone. [Work supported by ONR Code 321 SS.]
Modal analysis of musical instruments using TV holography
Authors: Rossing Thomas D.
Published: July 2012

Holographic interferometry gives the greatest spatial resolution of any method of modal analysis. However, recording holograms on photographic film is time consuming and often inconvenient. Electronic systems that use CCD TV cameras to record images and form the interferograms in a small digital computer avoid these inconveniences. In a typical electronic TV holography system, a new interferogram is displayed 30 times a second, providing the opportunity to view the interferograms in real time as some parameter is varied. We illustrate this method by describing the vibrational modes of several musical instruments, including bells, gongs, cymbals, drums, violins, cellos, guitars, mandolins, and steelpans.
Acoustic and modal analysis of an African djembe drum
Authors: Russell Daniel A. , Haveman Wesley S.
Published: July 2012

The African djembe drum consists of a goat skin stretched over a hand-carved shell with a large cavity, open at the bottom. The shape of the shell cavity acts as a Helmholtz resonator, providing a strong bass component around 75 Hz. The shell exibits several bell- or wineglass modes, some of which have frequencies close to membrane modes. This talk will present results from acoustic and modal analysis tests of the drum with and without the skin membrane intact. Mode shapes and frequency spectra will be presented as well as a discussion of how the shell, cavity, and membrane couple together to provide the djembe’s unique sound.
Bilingual speakers perceive a musical illusion in accordance with their first language
Authors: Deutsch Diana , Henthorn Trevor , Dolson Mark
Published: July 2012

The tritone paradox is a musical illusion that is perceived quite differently by different listeners. Previous findings have indicated that perception of this illusion varies with the language or dialect to which the listener has been exposed, particularly in childhood. In this study, subjects were employed whose first language was Vietnamese and who now reside in California. One group of 16 subjects had arrived in the U.S. as adults. All spoke perfect Vietnamese but little English. Another group of 16 subjects had arrived in the U.S. as children. All spoke perfect English, but most did not speak fluent Vietnamese (though they still heard some Vietnamese spoken). The two groups perceived the tritone paradox in strikingly similar ways, and their perceptions differed significantly from those of another group of Californian subjects who were native speakers of American English. Another experiment, employing fluent Vietnamese speakers, obtained a close correspondence between the way a subject perceived the tritone paradox and the pitch range of his or her speaking voice. The bilingual subjects, therefore, perceived the tritone paradox in accordance with the pitch characteristics of their first language, even when they no longer spoke this language fluently.
Nonlinear modeling of the ‘‘mitnahme-effekt’’ in coupled organ pipes
Authors: Stanzial Domenico , Bonsi Davide , Gonzalez Diego
Published: July 2012

Two slightly mistuned organ pipes of the same nominal tone placed on neighboring holes of the same groove of the slider chest can synchronize if simultaneously sounded. The frequency difference between the two pipes disappears (mitnahme-effekt) giving up on a common frequency which is, in general, slightly higher than both natural frequencies of the pipes [Angster et al., ‘‘Coupling between simultaneously sounded organ pipes,’’ AES preprint 3534 (F1-2), Berlin (1993)]. A related phenomenon is observed when the separation between the two natural frequencies is bigger than 1%: this gives up on an increased difference frequency. This paper shows that a numerical simulation, where the two coupled pipes are modeled with a pair of coupled nonlinear oscillators, qualitatively obtains both these results. Furthermore the existence of a parameter range fitting all the experimental data is presented.
On the square-root distance dependence of sound field near an edge of a semi-infinite plane
Authors: Ueda Mitsuhiro
Published: July 2012

It is known that the 2-D sound field near an edge of a semi-infinite plane depends on the square-root of a distance between the observation point and the edge. The boundary value problem for the potential on the semi-infinite plane is formulated using a new principle of diffraction, that is, virtual discontinuity principle of diffraction (VDPD). According to this formulation, a new response function, that describes mutual dependence of potentials on the plane, is obtained and is localized near the edge. Since the square-root distance dependence also appears only near the edge, it becomes clear that the dependence can be explained by the analysis localized near the edge. Consequently the boundary value integral is carried out for a very short interval including the edge assuming that the observation point is very near the edge. The square-root dependence arises from the restriction that the same potential is reconstructed from the integration over the short interval. It is interesting to note that the new response function contains a scheme in it to fix the distance dependence of potential at points near the edge.
On the model of propagation of high-velocity subsurface waves
Authors: Nesvijski Edouard G.
Published: July 2012

There are a great number of theoretical and experimental works published on the problem of analysis and classification of surface waves, but some recent experimental results cannot be explained unambiguously by existing basic theories because the velocity of registered waves is considerably higher than expected. For a better understanding of this phenomenon it is proposed to take a fresh look at the classical elaboration of the Rayleigh problem. This paper considers additional real roots of the Rayleigh equation in an attempt to explain the existence of a special type of high-velocity leaky waves propagating under the surface of half-space solid bordering with vacuum or gas. Their main energy concentrates in a local zone under the surface, and below this zone they transform into bulk waves taking away the wave energy. Some computer simulations and calculations are presented as a theoretical explanation of the conditions of high-velocity leaky subsurface waves propagation. An original representation of the Rayleigh function in 3-D gives one the opportunity to better understand the physical nature of the subsurface wave behavior in solids with different elastic characteristics. The proposed model of propagation of high velocity subsurface waves fits well with experimental data.