bluuebunny/crossref_metadata_2025 huggingface dataset:
High resolution acoustic characterization and change detection to evaluate hurricane effects on a coastal bay bottom
Authors: Freeman Angelina M. , Roberts Harry H. , Banks Patrick D.
Published: September 2008

Using high-resolution acoustics (sidescan sonar, chirp sonar subbottom, and echo sounder profile data) the shallow surface and subsurface of Sister Lake (Terrebonne Basin) of coastal Louisiana’s deltaic plain was imaged pre- and post-hurricanes Katrina and Rita. The pre-hurricanes survey in May 2005 imaged the entire lake bottom. To assess the effects of hurricanes Katrina and Rita, a second survey in October 2005 included acoustic resurveying of corridors of data covering all major sectors of the lake. Regions of sidescan reflectance differences between pre- and post-storm periods, corroborated with regions of onlapping sediment or zones of scour in the chirp sonar subbottom data, show areas both of sedimentation and erosion between surveys. Ground truth box cores were collected to calibrate acoustic data. Preliminary image processing results of the georeferenced pre- and post-storms sidescan datasets indicate 60% of the area experienced sedimentation and 40% was scoured between surveys. Amplitude reflectivity of chirp horizons were mapped, and incorporated with sidescan amplitude and texture attributes in change detection analysis. Standardized digital processing, supervised classification, and change detection techniques are developed to characterize the bay bottom and shallow subsurface and to assess and quantify storm effects. [Work supported by NOAA NA03NMF4520316.]
Monitoring hurricanes using infrasound
Authors: Talmadge Carrick L. , Hetzer Claus , Gilbert Kenneth E. , Waxler Roger
Published: September 2008

The University of Mississippi is leading a multi-institutional collaboration to monitor hurricane activity using infrasound, in particular the microbarom signal produced by any strong cyclonic storm. Monitoring technologies currently in use do not permit accurate long-term predictions of hurricane intensity, nor in general even for the rapid warning of sudden intensification of the storm strength. The current status of the hurricane acoustic monitoring system, including advances in sensor technology at the NCPA, will be reviewed. The potential for microbaroms to be used as an indicator of storm strength and as a metric to aid in predicting future changes in storm strength will be discussed.
Underwater surveys after the storm
Authors: Alleman Peter J
Published: September 2008

Following hurricanes Katrina and Rita, many types of acoustic systems were used to assess the effects of the storms. Swath multibeam sonars were used to survey erosion in ports, channels, and estuaries. Sidescan and scanning imaging sonars were used to locate debris, obstructions, missing oil platforms and ships, and dislocated pipelines. Acoustic positioning systems and acoustic modems were used to support the sonar imaging systems. A wide array of acoustic systems were used in the overall effort. Samples of data from several types of sonar systems will be presented along with discussions of the challenges of collecting data in a real-world environment.
Infrasound measurements during hurricane Katrina
Authors: Wagstaff Ronald , Goggans Eric , Rice Heath , Talmadge Carrick
Published: September 2008

Infrasound is used to detect both natural and man-made events. Microbarometric measurement stations have been placed worldwide in order to detect infrasonic signals in the atmosphere. Such signals range in frequency from less than 0.01 to 10 Hz. Infrasound is produced by many natural phenomena including violent storms, gravity waves, the Aurora Borealis, and even some animals. Because infrasound signals have such low frequencies, they can travel great distances in the atmosphere, while maintaining good temporal coherence. This makes the atmosphere an excellent medium for infrasound signal propagation and corresponding detection of large storms, such as hurricanes and tornados, which generate strong infrasonic signals. This paper will discuss hurricane Katrina’s infrasound spectral results obtained from data measured by piezo-ceramic infrasound sensors in Oxford, MS, about 400 miles to the north of New Orleans. Spectral and temporal coherence results will be presented and discussed. [Work supported by ARDEC.]
Generation of microbaroms by hurricanes
Authors: Hetzer Claus , Talmadge Carrick L. , Gilbert Kenneth E. , Waxler Roger
Published: September 2008

Under quiet conditions, a background peak at approximately 0.2 Hz is observed worldwide on infrasound stations. The peak is understood to be the ‘‘microbarom peak’’ associated with ocean waves. The intensity of microbaroms increases dramatically on inland infrasound stations when a hurricane is offshore and within a few thousand km. Hurricanes, thus, are unique phenomena for investigating microbarom generation by ocean waves. We review recent microbarom data and examine existing theories for the generation of microbaroms. In particular, we propose two possible models for the generation of microbaroms by hurricanes. In the first model, the microbaroms are generated near the eye of the hurricane, and in the second model, by counter propagating ocean wave fields created by the hurricane and relatively far from the eye. Bearing data from infrasound stations are presented that support the second model. [Supported by the U.S. Army Space and Missile Defense Command.]
Is higher resolution bathymetry always better for undersea sound propagation modeling?
Authors: Arvelo Juan
Published: September 2008

Bathymetry is one of the most important environmental parameters affecting undersea sound transmission in shallow waters. There has always been a preference towards bathymetry with the highest resolution and accuracy when conducting sound propagation modeling. However, extreme care must be exercised in the selection of the correct bathymetric resolution. It will be demonstrated that the correct resolution depends on the source of the geoacoustic model used. Higher resolution bathymetrics, such as multibeam surveys, introduce steeper slopes that yield larger bottom losses. If a lower resolution bathymetry was implemented to conduct geoacoustic inversion, then the same bathymetric resolution must be used to conduct subsequent sound transmission modeling. In addition, when geoacoustic inversion results are reported, the bathymetric resolution used should also be reported.
An autonomous underwater vehicle as sound source for geoacoustic inversion
Authors: van Leijen A. Vincent
Published: September 2008

During the MREA07 trials an autonomous underwater vehicle (AUV) was deployed to run a bathymetrical survey in a shallow water environment off the coast of Italy. Apart from much coastal and recreational activity in the area, self-noise of the REMUS AUV was continuously observed on a sparse vertical receiver array that was deployed from a small boat at anchor. As the vehicle ran its survey with a speed of 5 kts and at a depth of 30 m, the propulsion system radiated harmonic related tones of low frequencies that were received in strong interaction with the sea bottom. Three selected tones were then exploited for the geoacoustic inversion of a local range-independent environmental model. The inverted parameters describe a soft sediment layer on top of a hard sub bottom; the obtained model with specified uncertainty is shown to match seismic and bathymetric data of the area.
Accuracy of passive matched-field, thick-sediment inversions in range-dependent environments
Authors: Del Balzo Donald , Pflug Lisa
Published: September 2008

Accuracy of shallow-water acoustic predictions is severely limited by uncertainty in sediment property characteristics. Recent research, using inverse methods to invert signals from controlled active sources, has been conducted to estimate seabed properties. However, some applications prefer a more covert approach. Our work is focused exclusively on passive, inversion techniques using signals from surface ships-of-opportunity. This study addresses the accuracy of low-frequency (∼100 Hz) matched-field correlations using broadband signals from surface ships with unknown source levels at unknown ranges. A range-staggered technique is employed to create a range-dependent sediment description, with ever increasing confidence as additional observations are made. Matched-field techniques are applied in a simulated shallow-water environment with a single vertical line array and high signal-to-noise ratios. The simulations indicate significant potential for accurate estimates of thick-sediment characterizations of grain size and layer thickness out to ranges of tens of water depths in shallow water, despite moderate mismatch conditions in the environmental model. [Work sponsored by SPAWAR.]
Acoustic scattering and propagation through spatially complex dispersive media via the direct numerical solution of the wave equation
Authors: Norton Guy V.
Published: September 2008

Analytical approaches for modeling propagation and scattering in inhomogeneous media are difficult, and often require extremely simplifying approximations in order to achieve a solution. To avoid such approximations, the direct numerical solution of the wave equation via the method of finite differences offers the most direct tool, which takes into account diffraction and refraction. It also allows for detailed modeling of spatially complex media. In all cases, the correct inclusion of the dispersive properties of the medium can make the difference in the interpretation of the results. However, the inclusion of dispersion directly in the time domain proved until recently to be an elusive problem. In order to model the transient signal, a convolution operator that takes into account the dispersive characteristics of the medium is introduced to the linear wave equation. In this work, numerical modeling of scattering from a variety of different dispersive media with physical properties associated with real world material is presented. Where possible, the numerical solutions are compared with a known solution. It is shown that in those cases, the use of the convolutional propagation operator leads to the correct solution for the scattered field. [Work supported by ONR/NRL.]
Effect of rough surface on received signals
Authors: Joseph Jeremy M. , Culver Richard Lee , Ballard Jeffrey A. , Jemmott Colin W.
Published: September 2008

The overall goal of our research is to incorporate knowledge of variability and uncertainty in received passive sonar signals into the signal processing. As part of this goal, we need to better understand the sources of this variability. It is well known that wave motion on the ocean surface can introduce significant effects on undersea acoustic signals. This talk focuses on predicting the impact of rough ocean surfaces on the variability of the received signal. An acoustics propagation code, range-dependent acoustic model (RAM) rough surface fine coarse (RRSFC), is utilized to simulate environments with flat and rough ocean surfaces. To explore the effects of random rough surfaces, a Monte Carlo method is applied to yield environment realizations with varying rough surfaces. From these simulations, probability density functions are generated and are compared with amplitude figures from environments with a flat surface in order to distinguish any overall effect on a received signal. [Work supported by ONR Undersea Signal Processing Code 321US.]
Tutorial lecture on weather and acoustics
Authors: Bedard Alfred J.
Published: September 2008

The relationships between sound and weather can be fascinating, frightening, useful, and at times mystifying. This tutorial lecture explores the range of intersections between weather and acoustics. Weather can affect acoustic environments causing noise increases, noise reductions, and sound focusing. One aspect of this tutorial reviews results from propagation modeling, indicating that under some conditions, the atmosphere can produce vertical wave guides. Conversely, sound can be used to actively interrogate the atmosphere and provide information valuable for weather prediction and warning. Probing capabilities reviewed, with examples, show that wind profiles, temperature profiles, wind shears, gravity waves, and inversions can be defined acoustically. There are also possibilities for monitoring other difficult-to-observe parameters such as humidity profiles. In addition, weather processes can generate sound, detectable at long ranges using lower frequencies. Specifically, observing networks have observed infrasound from a growing number of meteorological events (e.g., severe weather, tornadoes, funnels aloft, atmospheric turbulence, hurricanes, and avalanches). Efforts to develop an infrasonic tornado detection system are described in some detail. Results indicate promise to help improve tornado detection and warning lead times, while reducing false alarms. Clear opportunities exist for infrasonic systems to provide operational weather data.
Transmission of impact sound in wood-framed construction
Authors: Quirt J. David , Nightingale Trevor R. T.
Published: September 2008

Ongoing studies in the flanking transmission facilities at NRC-IRC have developed a framework for predicting the overall sound transmission, including flanking, in wood-framed multifamily buildings. Power flow via each flanking path is affected by five factors that determine a path transfer function specific to the type of excitation (airborne or impact) and the construction details. This paper examines how common construction details affect transmission of impact sound between adjacent rooms, which are either side-by-side or one above the other. Since the source room floor is an element common to all impact flanking paths, a series of toppings were evaluated as treatment options. Additional layers of gypsum board and improvement due to resilient mounting were evaluated for the walls in the receiving room. Estimates of the resulting impact SPL were obtained by summing the energy transmitted by the direct path through the floor assembly separating the pair of rooms (if applicable) and all the flanking paths involving the relevant wall-floor junctions. These estimates provide the basis for a design guide to predict sound isolation in typical wood-framed row housing or apartment buildings.
Development of a two-parameter system for evaluating impact noise insulation
Authors: LoVerde John J. , Dong D. Wayland
Published: September 2008

Impact insulation is currently described with a single number metric impact insulation class (IIC), which correlates poorly with subjective reaction and does not often properly rank order acoustical performance of assembly components. Modifications to IIC have been proposed, but the methods are limited to changing the source or the metric. Experience indicates that impact noise can be divided into two broad classes: Low frequency thudding (e.g., footfalls) and mid/high frequency noise (e.g., heel clicks, dragging furniture, etc.). Low-frequency impact sound pressure level (ISPL) is generally influenced by different variables than the mid/high-frequency ISPL; the authors propose that the two are largely independent. Therefore, two domains are required to adequately characterize the impact noise insulation of an assembly [LoVerde and Dong, 33rd Inter-Noise Proceedings Paper 296, 167 (2004)]. A variety of candidate two-domain systems have been reviewed, where one domain describes the low-frequency performance and the second domain the mid/high-frequency performance [LoVerde and Dong, 14th International Congress Sound and Vibration Paper 476 (2007)]. The two domains are calculated using third-octave ISPL data obtained from recent field impact noise tests. The results suggest that a two-domain system offers considerable improvement over current single-number metrics for evaluating and designing assemblies.
Repeatability and reproducibility of field impact insulation class testing
Authors: LoVerde John J. , Dong D. Wayland
Published: September 2008

Field impact sound insulation in the United States is typically quantified in terms of field impact insulation class, which is defined in ASTM E1007. According to the method, the precision of this test method has not been established, and to our knowledge there have been no studies attempting to evaluate the precision of this type of measurement. Precision is typically defined in terms of repeatability and reproducibility, which will have different definitions for field and laboratory applications. Repeatability in the field may be thought of as the variation in acoustical performance when the test is repeated for the same specimen in the same location. Reproducibility in the field may be thought of as the variation in acoustical performance of the same design, constructed in different locations but in the same manner and with the same personnel and materials. The repeatability and reproducibility of a number of field tests of similar assemblies are calculated, and the precision of field impact testing is evaluated.
Impact noise and walking noise in multifamily housing
Authors: Lilly Jerry
Published: September 2008

Field measurements of impact sound transmission using the ISO standard tapping machine are compared with field measurements of human walkers in both wood and concrete buildings. In wood frame construction, low-frequency noise dominates the spectrum with most floor coverings. In concrete buildings, high-frequency noise is the controlling factor in non-carpeted areas. The relative effectiveness of different noise mitigation measures will also be discussed.
Building vibration excited by step dancing—Case study
Authors: Eligator Ronald
Published: September 2008

A new three-story building (steel frame, metal deck, concrete floor slabs) for the performing arts includes a dance studio on the upper level. An isolated concrete floor was installed within the dance studio, which is effective at attenuating impact sources (as modeled by a standard tapping machine), and normal foot fall (walking, light dancing, or similar). Hard-shoe, percussive dance (e.g., step dancing) by solo dancers and especially a chorus of 20 to 30 dancers, generates significant foot fall noise and vibration within the building, that is audible in the spaces one and two floors below the dance studio, and causes perceptible vibration of the building structure. Structural analysis relating natural frequency of building structure with natural frequency of isolated floor and forcing frequency of dancers was performed. Noise and vibration testing, with tapping machine and dancers, was also performed. Stiffening of slab with additional steel column to reduce effective span was effective in reducing magnitude of intrusive noise and vibration, as demonstrated by testing with dancer as source.
Acoustic characterization of in-room footfall noise
Authors: Rawlings Samantha B. , Magee Joshua A. , Celmer Robert D.
Published: September 2008

Existing literature concerning footfalls is primarily focused on its transmission between spaces, such as a floor/ceiling’s Impact Isolation Class. This study measured in-room sound power spectra produced by footfalls on eleven different floor surfaces using human subjects and a standard tapping machine. Within a reverberation room, 7 male and 7 female subjects walked on each floor while wearing 3 different types of footwear: Leather-soled with hard heels, rubber-soled with rubber heels, and sneakers. Sound power spectra were measured in 1/3 octaves using the procedures of ISO 3741. A tapping machine was also used on each floor profile using both standard drop weights and with cored samples of the same shoe soles attached to the bottom of each weight. The data for each floor profile produced averages by shoe type along with corresponding 95% confidence intervals. A total of 143 average sound power spectra were generated, based on eleven floors with thirteen averages per floor (3 male, 3 female shoes, 6 shoed tapping machines, and 1 bare tapping machine). Spectral results for each shoe/floor were studied and compared. Correlations between sound power spectra produced with human walkers versus tapping machine were investigated. [Work supported by The Paul S. Veneklasen Research Foundation.]
Ultrasound-assisted skin diagnostics
Authors: Paliwal Sumit , Ogura Makoto , Mitragotri Samir
Published: September 2008

The biomolecular composition of human skin, represented by a multitude of lipids, proteins, nucleic acids, and other miscellaneous molecules, is a sensitive indicator of skin’s local health, as well as the body’s systemic health. However, this information is not easily accessible, and consequently not used in the current diagnostic methods. To address the lack of quantitative methods for non-invasive skin diagnostics, herein, we describe the use of ultrasound to rapidly extract biological markers from skin. Specifically, we extracted several types of proteins (keratins, beta-actin, cytokines, and others), lipids (cholesterol, ceramides, fatty acids, and others), nucleic acids, small molecules (natural moisturizing factors and exogenous molecules), and microbes enabling us to create skin’s unique biomolecular signature. The extracted biomolecules showed quantitative correlations with their composition in the epidermal skin. Extraction of these entities from skin using our method is convenient and reproducible, thus making it an advantageous alternative to biopsy and tape-stripping. By quantifying changes in skin’s biomolecular profile, we report several specific in vivo applications of our method for assessing chemical-induced skin irritation, atopic dermatitis, and psoriasis in animal models. As a corollary to this technique, measurement of skin’s drug bioavailability in rats is also demonstrated.
Auscultation using ultrasound-Doppler techniques
Authors: Ahroon William A. , Houtsma Adrianus J. M. , Curry Ian P.
Published: September 2008

An earlier presentation described a hybrid instrument using electromechanical and ultrasound-Doppler techniques to permit auscultation in extremely noisy environments, such as Army medical evacuation vehicles [Houtsma et al., J. Acoust. Soc. Am. 120, 3361 (2006)]. That paper presented the theories behind the hybrid instrument and provided simulations of auscultation in noisy environments. An update on the progress since the first report is presented. In one study, recordings of cardiac and pulmonary sounds from healthy volunteers aboard an in-flight Black Hawk helicopter are presented. As anticipated, auscultation with the electro-mechanical (acoustic) mode was impossible inside the aircraft. Using the ultrasound-Doppler mode, all heart sounds and most lung sounds were clearly audible. The best-audible lung sounds came from the mid-axillary left and right locations. A second study was performed to determine if the hybrid instrument could be used to detect the difference in sound in a correctly versus incorrectly ventilated swine. After some experimentation with precise auscultation sites, the listener was able to detect both heart and lung sounds reliably in both electromechanical and ultrasound-Doppler modes. Recommendations to improve the performance of the instrument in the next iteration of the device are presented.
Developments in infrasound sensors and wind noise reduction
Authors: Bass Henry E , Talmadge Carrick , Hedlin Michael , Walker Kris , Zumberge Mark , Garces Milton
Published: September 2008

As applications of infrasound grow so does the need for reasonably priced microphones and attendant wind noise reduction approaches. Many applications require sensor systems with frequency response between 0.01 and 10 Hz and a dynamic range between a few micropascals and ten Pascals and operate under severe environmental conditions. Sensor systems are often in remote areas with only occasional maintenance visits. Current installations usually employ classic condenser microphones or sliding wire microbarographs along with porous hose wind filters. Next generation sensors use optical fiber sensors long enough to average out wind noise or multiple sensors which allow for electronically canceling wind noise. Some of the advantages and characteristics of these sensors will be described. Calibration of sensors over the range of conditions remains a challenge. Progress on calibration facilities will be included in the discussion. [Work supported by the US Army Space and Missile Defense Command.]
Low frequency electret condenser microphone
Authors: Lawrenson Christopher C. , Zuckerwar Allan J. , Shams Qamar A.
Published: September 2008

A condenser microphone has been fabricated for measuring low-frequency sound pressure. The goal of this design is to keep the background noise as low as possible. The microphone features a high membrane compliance with a large backchamber volume, a prepolarized backplane, and a high impedance preamplifier located inside the backchamber. Methods for characterizing the performance of the microphone will be presented including background noise levels, which will be compared to commercially available microphones.
Helmholtz resonator as a mobile source of infrasound
Authors: Soto Hector L. , Zuckerwar Allan J.
Published: September 2008

A Helmholtz resonator is designed to obtain a single-frequency, high sound pressure level (SPL) source of infrasound with minimum distortion. This apparatus is used to provide a simulated point source for applications ranging from sound propagation studies to locating an infrasonic sound source using triangulation. The resonator is designed to yield a frequency of 20 Hz and a high quality factor. The presentation will show background theory, design of the resonator, results of a built prototype, and challenges in obtaining a clean pure tone signal using this system.
Optical fiber infrasound sensor arrays: Signal detection and characterization capabilities in the presence of wind noise
Authors: Walker Kristoffer , Dzieciuch Matthew , DeWolf Scott , Zumberge Mark , Hedlin Michael , Berger Jon
Published: September 2008

Optical fiber infrasound sensors (OFIS) are compliant tubes wrapped with two optical fibers that integrate pressure variation along the length of the tube with laser interferometry. The coherent signals traveling at acoustic speed are averaged along the length of the OFIS at the speed of light, while spatially incoherent noise traveling at wind speed is attenuated. We present new wind noise measurements, which augment initial work that suggested an OFIS has a lower noise floor above 1 Hz than a traditional microbarometer with a rosette pipe or hose filter in light wind. We also discuss OFIS configurations and techniques to determine the signal phase velocity direction. The instrument response is a function of the orientation of the OFIS relative to that of the wavefront. That property can be exploited to help determine the phase velocity of infrasound signals. This type of instrument-response-dependent beamforming is theoretically an improvement to standard beamforming for the same number of sensors when the signals are immersive or continuous in nature. When the signals are more impulsive in nature, the success of these techniques mostly depends on how successful the OFIS is in reducing wind noise and the signal bandwidth.
Simulation-based response analysis of porous and non-porous infrasonic arrays
Authors: Marston Timothy M. , Biwa Tetsushi
Published: September 2008

A numerical simulation for porous and non-porous infrasonic arrays has been developed to aid in the analysis of the response of these systems. For design flexibility, the simulation makes use of differential T-elements, which may be used as building blocks to assemble pipes and junctions of various shapes and sizes. The simulation adds to the capabilities of a previously developed model [Alcoverro and Le Pichon, J. Acoust. Soc. Am. 117, 1717 (2005)], by including variable tube porosity, a calculation of wall-losses based on a thermo-viscous function, a calculation of the change in response as the azimuth and elevation of the incoming wave are varied, and a calculation of the wave shape as it propagates through the array in the time domain. [Research funded by the Applied Research Laboratory Educational and Foundational Fund.]
Multipitch detection for piano music: Benchmarking a few approaches
Authors: David Bertrand , Badeau Roland , Bertin Nancy , Emiya Valentin , Richard Gaël
Published: September 2008

When trying to find a solution to the critical and sometimes ill-posed problem of multipitch estimation, it is common to have to choose between several approaches: Using a processing that resembles that of the human auditory perception, or using a decomposition adapted to the spectral content of the targeted sound category, taking into account an a priori knowledge of the spectral properties of musical notes or trying to learn some of its charateristics or even more, to run an algorithm that blindly tends to separate the sound into multiple elementary entities. This work involves some recently published techniques, such as the non-negative matrix factorization with sparsity constraints, a likelihood approach, based on a smooth spectral envelope model for both the background noise and for the partials, and a deterministic method combining spectral and temporal criteria. Their performance is comparatively assessed on a common multipitch database restricted to piano music, drawn both from home-made recordings and soft-synthesized sounds. The results are discussed with respect to the complexity, the versatility, the sensitivity to fine tuning, and the precision reached by each approach. [This work is granted by the French Groupement des Ecoles de Télécommunication (TAMTAM project).]
Melody-based retrieval in audio collections
Authors: Marolt Matija
Published: September 2008

Mid-level representations are increasingly used to bridge the gap between high-level (semantic) and low-level audio representations. A mid-level representation that integrates melodic and rhythmic aspects of a music signal is introduced. The representation is formed by first performing multi-pitch detection on consecutive audio frames, and then searching for dominant melodic lines within the detected pitches. Beat-tracking is also performed to yield a beat-synchronous representation, independent of tempo variations. The representation is used as the basis for a melody-based audio retrieval system. An approximate nearest neighbor search algorithm is employed to compare sections of the mid-level representation of the query to indexed sections of mid-level representations of songs in a collection. Symbolic queries may also be used. Results are ranked according to the number of matched sections. A locality sensitive hashing function for cosine similarity is used for indexing, and the point location in equal balls algorithm for searching. Retrieval was tested on the cover song identification task, where the goal is to retrieve different interpretations of a song in a collection. Results on a collection of 2,400 songs are presented. [Work supported by ARRS.]
Query-by-singing/humming systems based on speech recognition technologies
Authors: Suzuki Motoyuki , Ito Akinori , Makino Shozo
Published: September 2008

While many query-by-singing/humming systems have been developed, several problems have prevented their practical use. For example, pitch extraction methods are commonly used in QbSH systems, but they often yield inaccurate information. To rectify this problem, a QbH system (i.e., no lyrics required), which uses multiple pitch candidates, has been developed. For each input note, multiple pitch candidates are extracted, and all combinations of pitch candidates are considered in the retrieval step. This system has shown higher performance than QbH systems, which use single pitch candidates. QbS systems (i.e., lyrics required) have also been developed. In this case, one of the biggest problems is to segment an input singing voice into musical notes. Several methods have been proposed. However, it is hard to segment the singing voice without linguistic information. In the proposed system, a lyrics recognizer outputs several hypotheses for a recognition result. Each hypothesis gives time alignment information between the singing voice and the recognized text. Once this information is available, it becomes easy to segment the input singing voice into musical notes, and a hypothesis can be verified from a melodic point of view. This system, which has 156 songs in the database, yields 93% retrieval accuracy for a query consisting of five notes.
Prediction of sound fields in a long enclosure due to a dipole source
Authors: Lai Chenly Y. C. , Li Kai Ming
Published: September 2008

The speech intelligibility in long enclosures is primarily affected by two factors: The reverberation time and the signal to noise ratio. To predict the speech intelligibility, previous studies were mainly focused on predicting either the sound field or the reverberation time in long enclosures. In these predictions, the sound sources were usually assumed to be a monopole source. However, it is well known that many noise sources have distinct directional characteristics. For example, noise radiated from railway vehicles and from ventilating fans is best modeled as a dipole source. This paper presents a numerical model to predict the sound field due to a dipole source in a long enclosure. The numerical model is validated by field measurements. The experimental dipole source was built by using a pair of identical loudspeakers placed at a close distance to each other that generate sound at equal amplitude but opposite in phase. Measurements are conducted at two test sites. Tolerable agreement between numerical predictions and experimental data is obtained.
Sound field modeling in urban squares using a diffusion equation model
Authors: Jing Yun , Xiang Ning
Published: September 2008

A diffusion equation model which has been recently applied to room-acoustic prediction is used to model the sound field in urban squares surrounded by diffusively reflecting building facades. A previous diffusion equation model [V. Valeau, et. al., J. Acoust. Soc. Am., 119, 2006, pp. 1504–1513; Y. Jing and N. Xiang, J. Acoust. Soc. Am. 121, 2007, pp. 3284–3287; A. Billon, et. al., Applied Acoustics, 2007, in print] is more suitable for room surfaces with low and medium absorption coefficient, whereas in this case the space is featured with an open top characterized by the absorption coefficient 1.0. Another diffusion equation model [T. Polles, et. al., J. Acoust. Soc. Am., 116, 2004, pp. 2969–2983] can well model the sound field in a space where one specific dimension is larger than the others, like street. However, it has not yet been extended for urban squares. A modified diffusion equation model is proposed for modeling the sound field in urban squares. Both simulations and scale-model experiments are employed to investigate its effectiveness in terms of the reverberation time and sound pressure level distribution.
Development of a low cost microphone array system for vehicle noise source identification
Authors: Silva Yuri Adson Ribeiro , Fonseca Willoium , Gerges Samir N. Y. , Mobley Joel
Published: September 2008

The evolution of data acquisition systems and the resulting cost reduction allow a higher channel count system to be used in the development of noise source identification systems. Unfortunately, the cost of measurement microphones remains impracticable for most applications containing dozens of channels. To overtake this problem, it is possible to use low cost sensors with a duly magnitude and phase response characterization. This article will present the low cost microphone array systems design and evaluation with 32 microphones. The microphones were constructed with electrets cartridges and mounted with an electronic preamplifier circuit. Different shapes for the sensors’ placement were computationally simulated for the adequate choice of the array geometry. The signal processing and data acquisition are implemented in a commercial platform. This allows the development of algorithms based on the beam-forming technique to obtain noise maps overlapped to the photographic image of the analyzed system. The goal of this work is to present the design, construction, and qualification of the 32-channel noise source identification system for applications in the automotive industry.
Air turbulence-induced vibration of SCUBA breathing apparatus
Authors: Donskoy Dimitri , Imas Len , Yen Timothy , Sedunov Nikolay , Tsionskiy Michael
Published: September 2008

The first study of the underlying mechanism of noise generation in SCUBA was reported at the previous 153rd ASA meeting (D. Donskoy, Acoustic Emission Mechanism from Scuba Diving Equipment). It was shown that the primary originating source of SCUBA vibration and subsequent acoustic emission is a combination of non-stationary shocks and separated turbulent flow that occurs within the first stage air pressure regulator during the inhale phase of breathing. The separation mechanism is due to a combination of two factors: Shock-induced separation and geometrical discontinuities in the regulator’s internal surface topology. The separated flow manifests itself through the presence of three-dimensional vortices and turbulent pressure fluctuations that excite structural resonances of the regulator and connected air tank, resulting in a complicated resonance dynamic behavior of the system. For the air flow dynamic analysis, we utilized a scale-adaptive detached eddy simulation model, which is based on the solution of unsteady, three-dimensional compressible Navier-Stokes equation solved on a hybrid unstructured computational mesh. The CFD simulations were applied to different topologies representing major types of regulators (piston and diaphragm types) to reveal the complex mechanics of the flow and their dependence on the regulator design. [Work supported by ONR.]
Time-domain observations of fast and slow ultrasonic group velocities in microsphere suspensions
Authors: Mobley Joel , Heithaus Robert Evans
Published: September 2008

In dispersive media, propagating wave packets can exhibit abnormal group velocities that differ substantially from the phase velocity of the dominant mode comprising the pulse. Recently, both arbitrarily large and negative acoustic group velocities were shown to exist in an aqueous suspension of polymer microspheres, using a broadband measurement technique. In this talk, we report on the direct time-domain observation of abnormal group velocities in microsphere suspensions. These dispersion-related propagation effects include slow group velocities, where the envelope speed is reduced by as much as 25%, relative to the phase velocity, and fast group velocities, which can be arbitrarily large or negative. The role of signal bandwidth in creating pulses in which such group velocities are manifested is discussed. The practical limits of slowing the group velocity in microsphere suspensions is also explored.
Nonlinear phenomena in acoustics: Traveling waves, bifurcations, and singular surfaces
Authors: Jordan Pedro M.
Published: September 2008

Traveling wave solutions (TWS) are explored in the context of nonlinear acoustics. Exact solutions are given, including one involving the recently introduced Lambert W-function, along with asymptotic and stability results. Poroacoustic propagation under Darcy’s and Forchheimer’s laws is examined, as well as acoustic phenomena in thermoviscous fluids. Additionally, a connection between discontinuity formation in the TWS and the associated singular surface, which is known as an acceleration wave, is pointed out. Last, if time permits, applications to nonlinear kinematic wave phenomena (e.g., second-sound and traffic flow) are briefly noted. [Work supported by ONR/NRL funding (PE 061153N).]
Validation of laser Doppler anemometer measurements of power dissipation in an arbitrary termination
Authors: Jung Ki Won , Atchley Anthony A.
Published: September 2008

The two-microphone technique is commonly used to measure power dissipation in arbitrary acoustic terminations. This method is well established and provides reliable results when care is taken to avoid problematic microphone configurations (e.g., a pressure node at a microphone location or the microphone spacing being too small in comparison to the wavelength). A laser Doppler anemometer (LDA) technique of measuring power dissipation is discussed in this paper. The LDA method has several disadvantages over microphone methods, including cost of the equipment, the need to use periodic test signals, the need for tracer particles, and the need for a transparent duct. However, rather than being limited to fixed microphone locations and working under the plane wave assumption, the LDA method allows measurement of multiple components of the velocity field at numerous locations with arbitrary spacing in three dimensions. In this paper, the LDA method is validated by measuring the power dissipated in a variable RC load [Fusco and Ward, J. Acoust. Soc. Am. 91, 2229–2235 (1992)]. The results are also compared to those obtained with the two-microphone technique. [Work supported by the Penn State Graduate Program in Acoustics.]
The wave behavior in the simple 1 dimensional lattice
Authors: Chu Kanghyun , Kim Yang-Hann
Published: September 2008

The behavior of an acoustic wave in a periodic lattice was mathematically shown for both infinite and finite cases. For simplicity, the lattice is assumed to be composed of two kinds of medium in ABABABAB order for the infinite case, and BBBABABABABBB order for the finite case. For the infinite lattice, by using the Blochs theorem, the dispersion relation of the wave in the periodic lattice was driven. This gives an acoustic band gap (the frequency region that the wave cannot propagate) and negative group velocity. In addition, for the finite lattice, by using symmetry and the superposition principle, reflection coefficient (between the outer medium and the lattice surface) and transmission coefficient (through the finite lattice) were driven. It was then shown that the result of the finite case agrees to the result from the infinite lattice case, if the number of periods goes to infinity. Finally, possible applications by using what we have learned would be discussed.
A gradient index sonic lens based on acoustic metamaterials
Authors: Sánchez-Dehesa José , Torrent Daniel
Published: September 2008

We report a method to design and characterize broadband gradient index lenses. The lenses are based on two-dimensional sonic crystals, which are periodic arrangements of elastic cylinders embedded in air. It will be shown that gradient index sonic lenses built with rigid cylinders are more powerful than conventionally curved lenses. We also demonstrate that the designing possibilities increased by considering the mixture of two types of cylinders in the sonic crystal. So, a gradient index lens with zero reflectance at the surface is proposed by employing a mixture of aerogel and rigid cylinders. Finally, a multiple scattering theory has been employed to compare the performance of conventionally curved lenses and gradient index lenses. [Work supported by MEC of Spain and GVA of Valencia.]
Nonlinear ultrasound beams and Eckart streaming using interdigital transducers
Authors: Kamakura Tomoo , Maezawa Miyuki , Kamata Rui
Published: September 2008

The Inter-digital transducer (IDT) of X-Y LiNbO3 128 deg substrate has a rectangular aperture 10 mm×2 mm, and has a center frequency of 20 MHz. The transducer radiates ultrasound beams in two different directions at the Rayleigh angle, that is determined by the propagation speeds of the surface wave on the substrate, and of the longitudinal wave in water, the angle being ±22 deg to the plane normal to the aperture and containing the IDT center electrode. The fundamental and second harmonic sound pressure levels are measured along and across the beam, using a hydrophone whose active element is 0.4 mm in diam and whose frequency response is calibrated up to 40 MHz. The KZK equation is utilized to predict theoretically sound pressure amplitudes [T. Kamakura et al., Acustica 80, 332–333 (1994)]. Especially, the fundamental pressure curves are compared with the Rayleigh integral formula. It has been found that the KZK equation is almost useful. The Eckart streaming in the ultrasound beam is also observed using PIV.
Estimates of loudness enhancement and induced loudness reduction at short masker-target intervals
Authors: Oberfeld Daniel
Published: September 2008

Recent data by Oberfeld [J. Acoust. Soc. Am. 121, 2137–2148 (2007)] supported the hypothesis [Arieh and Marks, J. Acoust. Soc. Am. 114, 1550–1556 (2003)] that a forward-masker causes two processes influencing the loudness of a temporally proximal target tone. One process results in a shift in target loudness towards masker loudness (e.g., loudness enhancement) and decays within 400 ms. Induced loudness reduction (ILR) caused by the second process remains constant for several seconds. According to this model, an estimate of the effect of the faster-decaying process is the change in loudness level at a short masker-target interval (both processes are in effect), minus the negative change in loudness level at a long interval (only ILR is effective). At a 100-ms interval, loudness matches between a 2500-Hz target and a 500-Hz comparison showed that 2500-Hz maskers more than 10 dB higher in level than a 35-dB SPL target caused an increase in loudness. For a 60-dB SPL target, a loudness increase was found at a masker-target level difference of 30 dB, but not at smaller differences. At the 1000-ms interval, ILR was consistently observed. The estimated amount of loudness enhancement is compared to data from experiments using a same-frequency matching task.
Salient phase density model for the lateralization of binaural pitches
Authors: Zhang Peter Xinya , Hartmann William M.
Published: September 2008

Binaural pitches are sensations of pitch generated from a broadband noise having a narrowband boundary region where the interaural phase difference varies rapidly as a function of frequency. These pitch sensations are perceived to be lateralized in the head. A binaural model, the Salient Phase Density model, has been derived to predict the lateralizations. The model begins by separating the boundary from the background. Because the boundary is narrow, the boundary components can be represented statistically by a density. Components of the boundary with phases similar to the background are discounted in the density as not salient. The density is then used to compute the cross-correlation function of the boundary region. The predicted lateralization is based on the interaural time difference of a template that best matches the cross-correlation of the boundary. The model was tested against psychoacoustical experiments using four types of Huggins pitch boundary-linear phase, stepped phase, uncorrelated phase, and π-shifted linear phase. The model was further tested against other binaural pitches: Binaural edge pitch and binaural coherence edge pitch. The experiments supported the model. [Work supported by the NIDCD, Grant No. DC00181.]
Lateralization of linear and logarithmic frequency-modulated (FM) sweeps at high frequencies
Authors: Saberi Kourosh , Hsieh I-Hui
Published: September 2008

The ability to lateralize linear and logarithmic frequency-modulated (FM) sweeps at high frequencies was investigated using a 2IFC adaptive block design. The FM stimulus swept from 3 kHz to 8 kHz with the onset frequency roved by 15% on each presentation. The cue to be detected was an interaural delay in the waveform’s fine-structure (i.e., delay in instantaneous frequency) that varied on each trial according to a 2-down 1-up adaptive rule. The waveforms to the left and right channels had simultaneous onset/offset envelopes. The stimulus duration (0.5, 1, 5, 10, 25, or 50 ms) and thus the sweep rate, as well as the sweep direction (up or down), were additional parameters of the study. Thresholds were higher than expected from studies of sinusoidal FM and ranged from approximately 100 μs for the 0.5 ms sweep to near chance for durations exceeding 10 ms. Sweep direction and type (log versus linear) did not substantially affect thresholds. Implications of these findings for models of binaural interaction at high frequencies and within-channel mechanisms of FM-to-AM transduction will be discussed. [Work supported by NSF.]