bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of joint channel estimation and data decoding for underwater acoustic communications with multi-carrier modulation.
Authors: Morozov Andrey K. , Freitag Lee E. , Preisig James C.
Published: October 2010

The current state-of-the-art in high-rate acoustic communications is represented by adaptive multi-channel equalization of single-carrier wideband signals. An alternative technique with significant potential for achieving high bit rates over multipath-distorted (frequency selective) channels is multi-carrier modulation (MCM). There are obvious technical advantages of MCM. Each frequency channel of MCM can be transmitted using a relatively narrow-band, high-efficiency transducer, and low-power amplifier, which allows achieving a very broad bandwidth. Use of narrow-band channels increases the tolerance for time synchronization errors in multipath array processing. Each frequency channel has a relatively low delay spread when measured in symbol units and can be equalized with low-complexity algorithms and simplified array processing. The reduction of the ISI span in each sub-channel allows for the application of soft decision decoders optimal for joint channel estimation and data recovery such as maximum-likelihood sequence detectors (MLSDs) and adaptive BCJR MAP algorithm. The adaptive form of the MAP algorithm is considered. The combination of channel shortening equalization and a practical MLSD algorithm with dual loop feedback and pre-survivor processing were tested in shallow water acoustic communications experiments and shown a very good performance. [Work supported by ONR Grant N00014-07-1-0229.]
Development of a measurement system for obtaining head relative transfer function of a head and torso simulator.
Authors: Vistosi Agustín , Vechiatti Nilda , Gavinowich Daniel
Published: October 2010

The human being, because of his complex audition system, has the ability to identify the spatial position of any sound from the surrounding environment. The objective of this work is to develop a measurement system that enables to mathematically model the hearing system by using a set of transfer functions. These equations, called head related transfer function (HRTF), synthesize mathematically the binaural transformation that the listener produces (principally from the torso, the head, and the pinna) in the audition process. To find the HRTF, the measurement system uses an acoustic dummy called head and torso simulator. With two microphones located in their ears, this dummy captures the sound with the same binaural properties as a real listener. The mathematical process to obtain these transfer functions is based on the LTI systems theory, using as excitation signal the sine sweep. Matlab was chosen for the processing environment, taking advantage of its flexibility on the digital sign process and their powerful computational tools.
Newton’s third law and seismic boundary conditions in poroelasticity.
Authors: Sahay Pratap
Published: October 2010

It is known that the application of Newton’s third law of motion on porous-porous welded contact implies that the total force exerted on the interface by one side is balanced by an equal and opposite force exerted on the interface by the other side. Here it is shown that Newton’s third law of motion also amounts to the continuity of the solid and the fluid phasic forces of the two sides at the interface as well as the equalization of the solid and fluid phasic forces on each side. That is, at the interface all forces are equal to one another, and that holds true irrespective of the alignment of the pores at the interface. That, in turn, also suggests that the velocity field associated with the total mass of poro-continuum is continuous at the interface. In conjunction with the requirement that the total energy must be conserved these yield the continuity of a weighted difference of solid and fluid velocities at the interface. Here, the weight factor is the product of the reciprocal density of the poro-continuum and the difference of the reciprocal densities of the two phases. The boundary conditions thus constructed uphold Newton’s third law of motion.
Wave propagation prediction with elastic boundary conditions.
Authors: Clark Cathy Ann
Published: October 2010

A bottom model which includes compressional and shear wave transmissions and reflections through a sediment layer is utilized to derive a single bottom reflection coefficient which is shown to successfully reproduce resonance effects due to shear wave conversion in various types of sediments. The consolidation of an infinite number of reflections and transmissions into a single coefficient is accomplished by formulating an infinite sum of matrices and expressing the result as a convergent series. The resultant approach achieves significant computational efficiency in comparison to performing an iterative search for mode eigenvalues. Comparisons of boundary calculations to other published results are presented and propagation predictions obtained by implementing the method in a normal mode model are compared to a number of measured data sets. [Work supported by the Office of Naval Research under the In-House Laboratory Independent Research (ILIR) Program.]
The effect of shear wave dispersion on bottom loss from unconsolidated sediments with rough interfaces.
Authors: Isakson Marcia J. , Chotiros Nicholas P.
Published: October 2010

Shear waves are often neglected for unconsolidated ocean bottom sediments like sands; however, the shear mode in these sediments can influence propagation and bottom loss especially for relatively high shear wave speeds and rough sediment/water interfaces. Although measured shear wave speeds are low, these measurements were made at frequencies much lower than the operating frequencies of most imaging or bathymetric sonars. New models for unconsolidated sediments suggest that shear wave speed may have a steep dispersion implying significant shear wave speeds at operating sonar frequencies. [Chotiros and Isakson, J. Acoust. Soc. Am., 116, 2011–2022 (2004).] Additionally, measurements for bottom loss suggest a dependence of shear speed on frequency. [Isakson, Yarbrough, Chotiros, and Piper, J. Acoust. Soc. Am., In review.] Lastly, although there is often low coupling between waves of vastly different sound speeds for shallow grazing angles on flat interfaces such as in long range propagation, interface roughness can steepen the local grazing angle leading to increased coupling. In this study, the effects of predicted shear wave dispersion and coupling through rough interface scattering on bottom loss and propagation for shallow water waveguides with unconsolidated sediment bottoms will be explored using finite element modeling. [Work sponsored by Office of Naval Research, Ocean Acoustics.]
Studies on the effect of shear on compressional wave dispersion.
Authors: Potty Gopu R. , Miller James H.
Published: October 2010

The results of a study to examine the effect of shear on compressional wave dispersion are presented. Modal arrival time data from different shallow water sites will be analyzed to examine the influence of shear. The modal travel times corresponding to the Airy Phase regions are extremely sensitive to shear. Simple inversion schemes will be developed to estimate the shear speed in the sediment by comparing theoretical predictions with experimental data. The estimated shear speeds will also be compared with shear speeds calculated from core data. The effect of shear on compressional wave attenuation will also be investigated. Synthetic data will be generated for elastic bottom, with different shear speeds, and these data will be inverted for compressional wave attenuation. One of the most promising approaches to estimate shear speed is to invert the relation between seismo-acoustic interface waves (Scholte waves) that travel along boundaries between media and shear wave speed. The propagation speed and attenuation of the Scholte wave are closely related to shear-wave speed and attenuation over a depth of 1-2 wavelengths into the seabed. A shear measurement system being developed at the University of Rhode Island based on this concept will be presented. [Work supported by the Office of Naval Research.]
Buffalo horns and the call of frogs: Some ancient free reed instruments from Southeast Asia.
Authors: Cottingham James P.
Published: October 2010

Construction and acoustical properties are described for two types of Southeast Asian free reed instruments of prehistoric origin. The mouth-resonated lamellophones common throughout the region are made by cutting three sides of the vibrating tongue from a single piece of wood, bamboo, or metal. The tongue cannot be plucked directly, but is excited by plucking the frame. The instrument is played by placing the reed tongue over the lips of the player using the vocal tract as a resonator. It is possible in some cases to produce tones by blowing as well as plucking. Uses of these instruments include imitation of the call of frogs in certain rituals and disguising of the voice. The free reed horn, chiefly used for alarm signals, funeral rites, and other ritual purposes, consists of a horn of a water buffalo or cow hollowed out and fitted with a single metal or bamboo free reed. Three pitches are possible, one with both ends of the horn open, one with the narrow end closed with a hand, and the third with both ends closed.
Reverberation and bottom-up cues in spatial selective auditory attention.
Authors: Ruggles Dorea R. , Shinn-Cunningham Barbara G.
Published: October 2010

Given multiple, competing speech streams, listeners can selectively attend to a desired stream using spatial cues made available by fine timing information arriving at the ears and passing to progressively higher regions of auditory processing. Reverberation smears fine temporal information needed for encoding important spatial cues, which may interfere with the ability to selectively attend to a target from a particular direction. To test this hypothesis, subjects were asked to focus spatial attention toward a location simulated directly in front of them and report a stream of digits from that location while ignoring two masker streams symmetrically positioned at 15 deg left and right. Three levels of reverberation were simulated to measure the influence of reverberant energy on performance. Results show that spatial selective attention degrades as reverberation increases and that overall performance varies dramatically from listener to listener in ways that are not predicted by age or memory span. Performance is highly correlated with absolute sensitivity to frequency modulation. Ongoing studies are exploring whether individual differences in performance on the spatial selection task are predicted by physiological frequency-following responses in the brain stem or by the process of aging.
Perceptual adaptation to room acoustics and effects on speech intelligibility.
Authors: Zahorik Pavel
Published: October 2010

The perceptual characteristics of sound in enclosed spaces are typically considered to be constant as a function of time, provided the source of sound also remains constant. Emerging evidence suggests, however, that at least for certain classes of room enclosures, the perceived acoustical contributions of the room decrease as listening time within the room is increased. A process of perceptual adaptation in which the acoustical contributions of the room are suppressed is likely responsible for this change. Here, a series of experiments is described that demonstrates objective improvements in speech intelligibility in reverberant rooms due presumably to room adaptation processes. Headphone-based auralization techniques were used to simulate the acoustics of various listening rooms used in the experiments, ranging from anechoic to highly reverberant space (broadband T60 = 3 s). When listeners were provided with brief (<10 s) room listening exposure via a carrier phrase prior to the test phrase used for intelligibility assessment, intelligibility improved by as much as 20%. Although variability in the effect was observed between listeners, it appears to require binaural input and is specific to moderately reverberant rooms (0.3 ⩽ T60 ⩽ 1 s). [Work supported by NIH R01DC008168.]
Development and validation of a new spatial impression descriptor.
Authors: Bidondo Alejandro
Published: October 2010

Working on the basis of the brain hemisphere specialization sound signal processing, this research seeks to continue previous experiments on the duration of the audition time integration window, now determining the incidence of diverse acoustic field variables in the spatial impression perception, developing a subjetive preference scale by means of the comparative judgement law and then verifying the validity of the previously developed descriptor. Sound field variables are the types of reproduction, stereo and surround 5.0, the initial time delay gap (ITDG), RT60 (reverb time), the relation direct to reflected energy (D/R) and mainly the generated integration window at the listener, keeping constant the total sound level at 79 dBA.
Effects of diffusing elements on perception of binaural sounds in concert halls.
Authors: Jeon Jin Yong , Kim Yong Hee
Published: October 2010

The perception of binaural sounds from the diffusing elements in concert halls has been investigated in terms of diffuseness. A rectangular recital hall with 480-seats was selected; the box-type diffusers, made of ceramic tiles with different heights, were installed for the lateral walls. The scattering coefficients of the diffuser profiles were more than 0.5 at the major frequencies. The frequency characteristics and the spatial distribution of the acoustical parameters were investigated at 17 positions. The early peaks were calculated as an in situ diffusivity index, which appeared as local maxima in the impulse responses. Auditory experiments at 8 receiver positions were carried out using the violin motif.
Three-dimensional laser Doppler vibrometry of the dry human skull.
Authors: Adamson R. B. , McKnight C. L. , Alian W. A. , Bance M. L. , Doman D. A. , Brown J. A.
Published: October 2010

The results of an experimental study of the vibratory response of the dry human skull at acoustic frequencies (250 Hz–16 kHz) are presented. In three dry skulls, the motor from a clinical bone vibrator, the BAHA Divino, was used to excite vibrations, and the amplitude and phase of the response were measured with a Polytech PSV-300 scanning laser Doppler vibrometer. Data were acquired at 2200 points covering the entire skull surface at ∼5 mm resolution. The experiment followed a stepped-sine paradigm with excitation frequencies spaced linearly at 200 Hz. The experiments show that the dry skull undergoes quasi-rigid motion at low frequencies, which breaks up into modal vibration patterns above 1000 Hz. At frequencies above 8000 Hz, clear standing wave patterns can be seen with wavefronts radiating out from the excitation location. The data are consistent with the response being primarily plate-bending motion. Progress of reproducing the data with a finite element model will also be reported. Geometry for the model was acquired using a high-resolution CT scan imported into HyperMesh® and the simulation was performed in LS-DYNA® hydrocode. [Work supported by the Atlantic Canada Opportunity Agency’s (ACOA) Atlantic Innovation Fund and the Natural Sciences and Engineering Research Council (NSERC).]
In vivo volumetric imaging of the mouse embryonic brain using chirp-coded excitation and a high-frequency annular-array.
Authors: Mamou Jonathan , Ketterling Jeffrey A. , Aristizábal Orlando , Turnbull Daniel H.
Published: October 2010

Many genetically engineered mice display abnormal development of the central nervous system (CNS) and high-frequency ultrasound (HFU) offers great potential for efficient, serial in vivo phenotyping of the developing embryonic mouse brain. However, HFU mouse-embryo imaging remains challenging because of the orientation of the embryos and of the limited acoustic penetration depth of HFU. In this study, a 34-MHz, five-element annular array was excited using conventional mono-cycle and chirp-coded excitations. Synthetic focusing and pulse compression (for the chirp excitation) were used to form images with increased depth of field and penetration depth (for the chirp excitation). In utero, in vivo 3-D data sets were acquired from 48 embryos over four stages from embryonic days E10.5 to E13.5, and CNS volume renderings were obtained. The chirp-based renderings were more morphologically accurate than the mono-cycle-based renderings, and the chirp provided sufficient penetration depth to correctly segment the brain ventricles lying deep inside the mother. The chirp renderings indicated that the early CNS architecture was dominated by the third and fourth brain ventricles, with the lateral ventricles contributing more at later stages. [Work supported by NIH Grant nos. NS038461 and EB008606.]
Analysis and simulation of industrial silencers by finite element method.
Authors: Mollinedo P. Helvio , Merodio V. Hector , Rabadan M. Itzala , Ortega H. Jose Angel
Published: October 2010

Many industrial processes and equipment require acoustic silencers to reduce the noise level radiated to the atmosphere. This paper presents the acoustic analysis of acoustic silencers by means of the finite element method. The numerical simulations of silencers are performed to evaluate the main features such as shape, length, and diameter, which must be considered in the silencer design. The results of this analysis permit to recognize important aspects that should be considered in the design of silencers. In general, the propagation of waves along the pipe can be reduced utilizing a dissipative or reactive silencer. The first one uses the absorbent properties of its walls to dissipate the acoustic energy. On the other hand, the reactive silencers reflect the sound waves backward (toward the source), avoiding the sound to be transmitted along the pipe. At present there are several experimental, numerical, and analytical techniques available for testing and design of silencers. This paper shows that the finite element method is a very useful tool for design and simulation of silencers with complex geometries.
The prehispanic Mayan musical instruments of the Yucatan Peninsula: An archaeoacoustic study.
Authors: Zalaquett Francisca , Ramos Alejandro , Medina Andrés
Published: October 2010

This project plans an archaeological and acoustic study of the musical instruments found during archaeological excavations in different archaeological sites in the Yucatan Peninsula, with the purpose of examining these materials with new analysis perspectives, including contexts, relationships with other registered materials, acoustic characteristics, and possible places, within the archaeological sites where they play those musical instruments. Our objective is to find and establish significant usage and meaning patterns of the prehispanic musical instruments in different places and moments (dance, songs, sacrifice, burials, etc.). We have the support of physicists from the Cybernethycs Laboratory and Mathematic Institute of the Universidad Nacional Autónoma de Mexico. This project includes physical methodology (Mobile Laboratory to measure the musical instruments in a control space), musical (to determinate musical intervals and tones used with more frequency), and archaeological (contexts) in the analysis of the musical instruments materials, methodology that allows us to obtain a dynamic comprehension and diffusion of the prehispanic musical maya instrument’s utilization.
From nose flutes to noise makers.
Authors: Hoekje Peter L.
Published: October 2010

Flutes in a wide variety of forms often tell important parts of the stories of their cultures. Four flutes dated from about 40 000 years ago give tantalizing hints of the role of arts and music in that prehistoric setting. Thousands of ceramic flutes have been found among Mayan ruins in forms that evoke the calls of birds as well as those that could be used for music. The nose flute was considered in some Polynesian societies to be the only instrument worthy of waking the king, because breath from the nose was not tainted by the lies that mankind speak from the mouth. Finger holes are arranged either to control the length of the air column, or in the ocarina type, their combined area affects the frequency of a Helmholtz resonator. However, the nose flutes from western Polynesia have an intermediate form and a more complex note pattern. Flutes are sounded by an air jet that may come from a fixed fipple or from the player’s mouth or nose. Variations as in the ney and the kawala allow the player much more control and a distinctive tone.
Urban space design based on the perceptual assessment of soundscape.
Authors: Jeon Jin Yong , Lee Pyoung Jik , You Jin
Published: October 2010

In the present study, urban soundscape has been investigated by social survey and soundwalking. An intensive social survey using 11-point numerical scale was carried out with narrative interviews; the dominant contexts affecting the perception of urban soundscape were derived from the survey: visual image, acoustic comfort, and natural brightness. Thus, the effects of contexts on the perception of soundscape were also confirmed by soundwalking. In addition, the effects of water sounds on the enhancement of urban soundscape were examined; auditory experiments were performed to enhance the perception of urban spaces with various kinds of water sounds. Water sound, which had 3 dB less than urban noise, was found as a preferable masker. Visual images, as well as acoustical characteristics of water sounds, had an effect on the perception of urban soundscape.
Classification of urban historic areas through multi-sensorial perception and expectation.
Authors: Maffei Luigi , Di Gabriele Maria , Brambilla Giovanni , Verardi Patrizio
Published: October 2010

The historic areas of cities are often under renewal processes. Although the general aims are to increase tourist attraction, to protect and restore the cultural heritage, and to improve quality of life for the local citizens, the renewal processes are generally based on architectural and design projects that privilege the visual perception. This approach does not take into account that the perception and enjoyment of the atmosphere in a historic area is a mix of phenomena that should be considered, and citizens and tourists perceive these phenomena in a dynamic way (e.g., walking along streets, crossing squares) and from different points of view. A new approach for the classification of urban historic areas is proposed. The classification is based on two emotional dimensions (calmness and vibrancy) determined by the variations of environmental parameters such as sound quality and light, and aesthetical parameters such as spatiality and urban degradation. Relationships between perceived soundscape and other parameters are under investigation on the basis of the data collected by interviews. A new approach to draw maps dealing with subjective perception and expectation is proposed in the view to be a tool for the urban renewal decisions and more effective and sustainable projects.
Soundscape classification using acoustical patterns analysis.
Authors: Fiebig André , Genuit Klaus
Published: October 2010

Urban locations can be characterized by acoustical fingerprints composed of specific sound sources dynamically emerging at certain times. This results in specific noise features and patterns of the soundscape, which allow for the identification of the urban place. To study this phenomenon at several locations distributed over the city of Aachen, short-term recordings of a few minutes with a binaural headset were made. Eight sites with different noise characteristics were chosen along a route through the city. Each location was measured twice with a certain time delay between the recordings to study the robustness of measuring the particular noise patterns and acoustical specifics of the respective place. The acoustical data as well as the subjective evaluations collected in situ on the basis of the soundwalk method were analyzed with respect to the identification of the uniqueness of the investigated places. The general aim of this study was to give recommendations and derive actions with respect to the preservation of pleasant noise features as well as the reduction of adverse noise aspects. The paper will highlight the feasibility of the approach as well as the applicability and acceptance of developed measures and actions.
Barcelona son-art project: Art and soundscape against noise.
Authors: Francesc Daumal i Domenech , Jimena De Gortari
Published: October 2010

The future of the city always is uncertain, but the reflection of the destiny of the uses of the ground and the indicators of mobility and activity allows us to raise a new line of design of its sonorous landscape. Especially in Barcelona, which has suitable conditions for it, with a little economic investment, although the elements of the dialogue between her and their citizens must be done. A first advance of the investigation Barcelona Son-Art that the equipment realizes on the repercussion in the habits of citizen conduct, mobility, election of house, etc., of the soundscape in Barcelona, and where some of the results of the methodologies, used in the Ph.D. thesis of the second participant, are shown.
Diffraction assisted rough ground effect.
Authors: Attenborough Keith , Bashir Imran , Hill Toby , Taherzadeh Shahram
Published: October 2010

Ground effect results from the interference between sound traveling directly from a point source to a receiver and that reflected coherently from the ground. The frequencies associated with first and subsequent order destructive interference in excess attenuation spectra are determined by the source-receiver geometry and the ground impedance. Typically if the ground is hard and smooth, then at grazing incidence the first destructive interference occurs at too high a frequency to be useful in noise control. However, the effective impedance of a rough, hard surface is finite, and destructive interference can occur at much lower frequencies over a hard, rough surface than if the surface is smooth. If the roughness is spaced periodically, then the phenomenon of diffraction assisted ground effect occurs. Instead of the single destructive minimum observed with randomly spaced roughness elements, a cluster of two or three destructive interference peaks are observed. This phenomenon has been explored through laboratory experiments using semi-cylindrical, rectangular, and wedge-shaped strips placed on a glass sheet. Use of multiple scattering theory for semi-cylindrical roughness on a hard surface shows that the diffraction assisted effect depends on the number of roughness elements and their spacing. The extent to which the phenomenon could be exploited for noise control is discussed. [Work supported by European Community FP7 project no. 234306.]
Cancellation of the acoustic field scattered from an elastic sphere using periodic isotropic elastic layers.
Authors: Guild Matthew D. , Haberman Michael R. , Alù Andrea
Published: October 2010

Periodic layers have recently been proposed as a means to obtain the material properties requisite for the creation of near-perfect spherical acoustic cloaking layers designed using coordinate transformation techniques. Previous work has suggested using radially periodic fluid layers that display an anisotropic density tensor in the long wavelength homogenization limit. Unfortunately, the high degree of anisotropy and functional grading necessitated by the coordinate transformation method and the use of fluid-like layers suggested by those techniques present significant practical challenges to their construction. An alternative to the coordinate transformation method is a non-resonant scattering cancellation technique that has been shown to provide up to 30 dB scattering reduction over a finite bandwidth using isotropic elastic layers. [M. D. Guild, A. Alù, and M. R. Haberman, J. Acoust. Soc. Am. 127, 1952 (2010).] The research presented here investigates the use of periodic isotropic elastic layers using the scattering cancellation technique to cloak an isotropic sphere. The work will specifically investigate the effects of the periodic layers having a non-zero shear modulus as opposed to being inviscid fluids as previously assumed. The results of this analysis will be presented and recommendations will be made regarding the effectiveness of a finite number of periodic elastic layers to cloak an elastic sphere.
Exponential amplification of evanescent acoustic waves and transparency through periodic stacks of planar surfaces.
Authors: Guild Matthew D. , Alù Andrea , Haberman Michael R.
Published: October 2010

Two of the most exciting properties of metamaterials are the possibility to sustain “growing” evanescent waves, which may provide sub-wavelength resolution, and transparency or cloaking effects. In this paper, we verify both these effects in periodic stacks of planar surfaces. We investigate this problem using Bloch wave analysis in order to determine the necessary requirements to achieve amplification of evanescent acoustic waves and overall transparency effects. This is achieved analogously to previous work for electromagnetic waves [A. Alù and Engheta, IEEE Antennas Wireless Propag. Lett. 4, 417–420 (2005)] by combining periodic arrays, properly designed to support conjugate Bloch wave properties, even though each stack individually operates in its stopband. Based on this conjugate condition, we have obtained several practical stack designs, formed by lumped passive acoustic elements, that may be able to amplify evanescent Bloch waves and provide complete tunneling and transparency at the frequency of interest. These findings may pave the way for acoustic imaging with sub-wavelength resolution and planar surface transparency.
Design of pentamode acoustic materials using homogenization and the adjoint approach.
Authors: Gokhale Nachiket H. , Cipolla Jeffrey L. , Norris Andrew N.
Published: October 2010

Acoustic metamaterials need to be realized using subwavelength microstructures. By tailoring the microstructure of the underlying unit cell, different effective properties at the macroscopic scale may be achieved. These macroscopic properties can be related to the microstructure using homogenization theory. The problem of designing a pentamode acoustic metamaterial is formulated as the minimization of an objective functional representing the difference between the homogenized properties and the target pentamode acoustic metamaterial properties. A quasi-Newton optimization approach is used to solve the optimization problem. Such an approach requires the gradient of the objective function with respect to the microstructural properties at every iteration, and hence the cost of gradient computation must be low. The gradient is calculated efficiently using the adjoint approach which requires the solution of only two (primal and dual) finite element problems, per homogenization deformation field, independent of the number of variables used to discretize the material properties. Resulting pentamode acoustic metamaterial microstructures are presented. [Work supported by ONR through Phase-I and Phase-II SBIR Contract no. NOO014-10-C-C0260.]
Acoustic frequency response inside a rectangular cavity.
Authors: Ng Gim Pei , Tan Cheah Heng
Published: October 2010

In any closed or partly closed regions of space, standing waves exist and the normal modes and natural frequencies associated with these standing waves determine the acoustic behavior of this enclosed air cavity. Also, there are many systems of practical interest in which a structure is in contact with this contained air. One of the practical examples considered in this study is the loudspeaker enclosures. The vibration behavior of the flexible membrane of loudspeaker is significantly affected by the modal contribution of the contained fluid and subsequently changes the frequency response of the speaker system. Thus, the objective of this paper is to study the acoustic behavior, which refers to the normal modes and natural frequencies of a rectangular air cavity and the coupled acoustic behavior of a force excitation source placed within this cavity. This study is then extended to an arbitrary cavity system. The second objective of this study is to locate the placement of the excitation source within the enclosed cavity that will contribute to a preferred acoustic frequency response within the frequency range of interest.
Value and interpretation of biometric evidence in forensic automatic speaker recognition.
Authors: Drygajlo Andrzej
Published: October 2010

Forensic speaker recognition is the process of determining if a specific individual (suspected speaker) is the source of a questioned voice recording (trace). Forensic automatic speaker recognition has proven an effective tool in the fight against crime, yet there is a constant need for more research due to the difficulties in adapting automatic methods of voice comparison to the forensic methodology that provides a coherent way of assessing and presenting recorded speech as scientific evidence. The ongoing paradigm shift in the forensic speaker recognition needs biometric methods for the calculation of the evidence value, its strength, and the evaluation of this strength under operating conditions of the casework. In such methods, the biometric evidence consists of the quantified degree of similarity between speaker-dependent features extracted from the trace and speaker-dependent features extracted from recorded speech of a suspect, represented by his/her model. This presentation aims at introducing deterministic and statistical automatic speaker recognition methods that provide several ways of quantifying and presenting recorded voice as biometric evidence, as well as the assessment of its strength (likelihood ratio) in the Bayesian interpretation framework, including scoring and direct methods, compatible with interpretations in other forensic disciplines.
Combining linguistic and non-linguistic information in likelihood-ratio-based forensic voice comparison: A hybrid automatic-traditional system.
Authors: Rose Phil
Published: October 2010

In the last decade, forensic voice comparison has experienced a remarkable paradigm shift [Morrison, Sci. Justice 49, 298–308 (2009)]. Both automatic and traditional phonetic approaches have been developed within the new paradigm. The main difference is that traditional approaches are typically local in both time and frequency domains, with features like formant frequencies extracted from linguistically comparable items (e.g., words or phonemes), whereas automatic approaches are typically global, with long-term spectral properties used and linguistic information treated as noise. Since neither makes use of all the information present, combining them could improve performance. A fully automatic and a partially traditional system were compared. Data were pairs of non-contemporaneous landline-telephone recordings of 60 speakers from the Japanese National Research Institute of Police Science database (net 35–40 s speech per recording). In the fully automatic system, the whole speech-active portion of the recording was analyzed using 12th order LPCCs, mean cepstral subtraction, GMM-UBM, and logistic-regression calibration. In the partially traditional system, the same procedures were applied only to tokens of [o:], [ɴ], and [ç] extracted from the recordings, with logistic-regression fusion of the results. The performance of each system and the fusion of the two were compared using the log-likelihood-ratio cost (Cllr).
Factors affecting the intelligibility of recorded speech: Considerations for forensic audio “best evidence”.
Authors: Boyczuk Jeff
Published: October 2010

Derived from a traditional common law rule of evidence, the “best evidence” standard as applied to recorded audio prescribes that an original recording, and not a duplicated or altered copy, will be presented in legal proceedings. The intent of this standard is to ensure that the integrity of the original evidence is preserved, such that a court is reasonably assured that it is being presented with the most complete and accurate record of the evidence. However, when considering forensic audio recordings of speech, which are frequently made in adverse acoustic environments, presentation of such recordings in their original form may not afford a court with the opportunity for a complete and accurate assessment of the evidence in question—namely, what words are being spoken on the recording? The current paper summarizes the technological and listener-based factors that should be considered when speech intelligibility is of prime importance in meeting the best evidence standard for presentation of forensic audio in court proceedings. Illustrative examples from recent court cases will be provided.
Witnesses’/victims’ recognition of a once-heard voice.
Authors: Bull Raymond
Published: October 2010

This presentation summarizes the results of three decades of research testing the validity of lay persons’ (e.g., witnesses’/victims’) ability to recognize the voice of a once-before heard stranger (e.g., a crime perpetrator). Studies around the world have consistently found that people are usually very poor at this task, even with short delays and adequate lengths of speech. Some courts have taken notice of this research and caution witnesses accordingly; however, in many cases voice line-ups have been poorly constructed and are therefore invalid. The final part of the presentation provides an account of some court cases in which I have participated as an expert.
Cross-correlation method for measuring ship acoustic signatures.
Authors: Chung Kil Woo , Sutin Alexander , Sedunov Alexander
Published: October 2010

Stevens Institute of Technology has been conducting research aimed at the development of a low-cost passive acoustic system for detection and classification of underwater and surface threats. The system uses several hydrophones where target bearing extraction is carried out by cross-correlation of the signal from paired hydrophones. The cross correlation method is constantly being improved by Stevens. This paper presents the recent improvements aimed at the separation and measurements of ship acoustic signatures in busy conditions (when sounds from many ships are received at the same time). The developed method is based on the cross-correlation calculation in two different time windows. The relatively large time window (up to 500 ms) is applied for ship bearing detections and full frequency spectra measurements. The short time window (2–5 ms) is used for measurements of detection of envelope modulation on noise acoustic signatures. The new algorithms calculating the modulation spectrum depending on the noise frequency allow finding the most modulated noise frequency bands. This gives additional information for ship classification. The developed methods were applied for measurements of various ship acoustic signatures in the Hudson River and in the NY Bay. [Work supported by the U.S. Department of Homelan.]
Remote localization of a moving target in a random scattering medium based on the Born approximation.
Authors: Rakotonarivo Sandrine T. , Walker Shane C. , Kuperman William A. , Roux Philippe
Published: October 2010

This paper presents a technique to remotely localize a moving target embedded in a fixed multiple scattering medium. The method, based on the Born approximation, does not require full modeling or even a moderately detailed knowledge of the multiple-scattering background. Using a multi-source/receiver laboratory setup in air, the technique was tested with experimental data at frequencies varying from 30 to 60 kHz (wavelength ranging from 0.5 to 1 cm) for centimeter-scale scatterers in a multiple scattering medium with 3% volume fraction. The method shows very good localization of the target with a precision of a few wavelengths.
Compressive sensing applied to audio signals using higher-order projections and the spatial domain.
Authors: Hoppe Elizabeth , Roan Michael
Published: October 2010

Compressive sensing (CS) is a new approach to data acquisition that is receiving much attention in the current literature. The main goal in CS is to accurately reconstruct a signal from a small number of randomly projected basis functions. The CS reconstruction accuracy hinges on the assumption that the signal can be projected into a sparse domain. A majority of the CS research to date has been focused on the application of CS to image processing. There has, however, been very limited research on the application of CS techniques to audio signals focused in two main areas: the use of the frequency and wavelet domains as the sparse signal domain, and the use of the spatial domain to perform compressive beamforming. In this work, two new approaches are examined. The first is the use of the spatial domain to reconstruct signals instead of simply identifying their direction of arrival. The second is the use of higher-order projection techniques (such as principal component analysis) as a sparse domain. This work will apply these techniques to speech signals to examine the ability of CS to reconstruct wide-band audio signals. In addition, the effect of additive noise on the reconstruction accuracy will be examined.
A dual space approach to beam tracing for optimal microphone placement.
Authors: Hoppe Elizabeth , Roan Michael
Published: October 2010

In many teleconferencing or video-conferencing applications, a high degree of speech intelligibility is difficult to achieve due to sub-optimal microphone placement in the room. In this work, beam tracing in the dual space is used to acoustically model an enclosed space with the goal of discovering optimal positions for microphone placement. In the majority of existing work, beam tracing is used to model empty rooms with simple layouts. This work allows for the addition of freestanding items, such as furniture or support pillars, and more complex room layouts. In addition, currently existing algorithms use beam tracing to predict and simulate the response of a source in a room at a specific location. In this work, both signals of interest as well as interferers will be included in the model. Instead of predicting the response at specific (x,y) locations, this work seeks to guide the placement of microphones for maximum speech intelligibility. The dual space representations for the reflected beams are generated for each source. These representations are overlaid on top of each other to highlight areas with the highest signal to interferer ratio.
Fan noise visualization and noise source identification by using nearfield acoustical holography.
Authors: Niu Yaying , Kim Yong-Joe
Published: October 2010

A nearfield acoustical holography (NAH) method combined with a non-stationary source compensation procedure is applied to identify the noise sources of two open fans. The measured noise data of a low-speed, small fan indicate the highest peak levels at the blade passing frequencies (BPFs) of 102 and 204 Hz. It is observed that there is no noise component induced by vortex shedding at the blade tips, or leading or trailing edges of the small fan. It is also observed that the structural resonance frequencies of the small fan blades are not coincident with the BPFs: thus, the structural vibration responses of the blades contribute insignificantly to the fan noise. The NAH results of the small fan show acoustic pressure fluctuations on the blade surfaces at the BPFs. The measured noise data of a high-speed, large fan show the frequency components associated with BPFs as well as vortices shed at blade edges. Similar to the small fan case, the resonance frequencies of the fan blades cannot be observed in the measured acoustic data. The NAH results of the high-speed, large fan successfully exhibit acoustic pressure fluctuations at BPFs as well as noise patterns radiated from the vortex shedding.
Synesthesia: Real/time image generation system based on the properties of an audio signal.
Authors: Jácome Andrade Hugo Fernando
Published: October 2010

This project involves a software that processes audio signals from a computer, transforming them into real-time images, similar to the Synesthesia. It used the Max/MSP/Jitter programming language; the system receives previously digitized audio and the software makes the analysis in fast Fourier transform parameters. These data shoot some analogies between sound and light parameters through the multiple incorporated graphical generators. A user interface offers the controls for the stage of audio analysis, visualization of spectrograms, sonograms, waveform, etc., plus dedicated controls to each one of the graphical generators, with specific options to modify figures, working mode of render, scale and saturation of colors, rigidity, surface density, etc. Each graphical generator has its independent operation, forming options, like geometric figures, rotatory planes, free edges membranes, and even real-time video modification with kaleidoscopic type effects, all of them product of the digital audio signals entering the system. This application was developed according to audio visual functions and any type of artistic programming, designed to be a friendly system with easy access and implementation.
A remote terminal unit multimedia.
Authors: Peña-Guerrero Maximino , Negrete-Redondo J. J.
Published: October 2010

One of the problems of remote terminal unit multimedia (RTUM) for the acquisition and data control in real time is the time it takes a process in carrying out calculations for one or more critical variables inside a supervision and control system. The system response to any change in these variables depends on this time delay. An RTUM is a computer system connected to a net thought to supervise and to control, in an automatic way, some of the electronic devices that exist in a multimedia recording studio. In order to reduce the inherent latency in the data capture, we have designed an RTUM with ASIC FPGA digital devices, whose functions written in VHDL are of specific purpose. Each device contains in its hardware a specialized function which is carried out in a parallel way inside a single clock cycle. In this paper we presented the description of the design of a remote terminal unit based in a digital microcomputer whose peripheral are ASIC FPGA standard devices, which are controlled by means of a general purpose microprocessor. The result is a control and acquisition multimedia data RTUM system with a smaller response time due to the parallel processing.
Interference techniques for determining large scale, three-dimensional structure of mixed fluid water column.
Authors: Badiey Mohsen , Katsnelson Boris
Published: October 2010

Propagation of acoustic waves can be used to map the 3-D structure of the water column with the horizontal scale about a few tens of kilometers. If the water column has oil, because of the vast contrast between the sound properties of the oil versus water (sound speed in oil is about 1300–1350 m/s), the index of refraction in the water column is changed. This change can be captured by acoustical sounding using source and vertical and/or horizontal hydrophone arrays and a 3-D structure of the water column can be constructed. To map the contours of oil patches and layers inside the water column in horizontal plane and its behavior in space and time, a variation of interference pattern in horizontal plane can be utilized. These interference patterns can be produced in an area of multipath propagation of sound rays due to horizontal refraction. In this paper, we provide theoretical estimation of position and velocity of boundary of a 3-D structure with sound speed distinct from surrounding (temperature front, internal waves, oil spill), using measurement of horizontal interference structure. It is shown that sound signals of different frequencies (from 50 Hz to a few kilohertz) can provide enough accuracy for mapping of similar inclusions.