bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Japanese expressive speech perception by Japanese and Taiwanese listeners
Authors: Huang Chun-Fang , Erickson Donna , Akagi Masato
Published: May 2008

Language is an important tool in speech communication. Even without the understanding of one language, we can still judge the expressive content of a voice, such as happiness or sadness. However, sometimes misunderstanding of emotional communication occurs. It is not clear what the common/different features are that help or hinder people with different culture/native-languages background in making judgments about the expressivity of speech. In order to explore this question, we focus on Japanese and Taiwanese listeners perception of Japanese expressive speech utterances. We used the perceptual model proposed by [Huang and Akagi, InterSpeech 2005; 2007], which involves a concept called "semantic primitives"-- adjectives for describing voice perception. This concept simplifies and clarifies the discussion of common/different features in terms of acoustic cues and expressive speech perception categories. Using this model, we found some common/different features in the perception of expressive speech. Specifically, our results suggest that there may be primary and secondary semantic primitives associated with acoustic speech characteristics which are involved in the perception of expressive speech, and that people from different cultures/native-language background tend to use the same primary semantic primitives in perceiving expressive speech but different secondary ones.
Production and perception of V1V2 described in terms of formant transition rates
Authors: Carré René
Published: May 2008

Vowels can be produced with static articulatory configurations leading to stable formant frequencies (targets). Here, an algorithm computes area functions according to the criterion of minimal deformation leading to maximal acoustic variations. Within this evolutionary dynamics, the deformations of the tube are not performed to reach targets, unknown during the process, but to move in the acoustic space in order to increase acoustic contrast. The corresponding formant trajectories in the acoustic space can be described in terms of formant transition rates. For example, following this dynamic approach, to produce [ae] from [a], the transition rates of F1 and F2 are necessary and sufficient to represent [e] and at the very beginning of the transition and throughout the transition there is sufficient information to detect [e]. This assertion means that the transition duration is more or less constant. Studies of V1V2 production and perception characterized by their formant transition rates are presented. Such a representation leads to new interpretations of vowel reduction, coarticulation, perceptual overshoot, hyper and hypo speech, normalization.
Voicing offsets and onsets in relation to intraoral pressure values in lingual obstruents of German
Authors: Koenig Laura L. , Fuchs Susanne
Published: May 2008

Phonation requires that tracheal pressure remain higher than intraoral pressure (Pio). In obstruent consonants, a major constriction in the upper vocal tract yields an increase in Pio, inhibiting phonation. The degree of Pio increase in consonants varies as a function of laryngeal and supraglottal apertures. Voiceless stops involve a rapid buildup and discharge of Pio, whereas fricatives involve more gradual changes in Pio. This work quantifies phonation offsets and onsets in German obstruents in relation to the Pio at these times. Pio signals were recorded via a pressure transducer affixed to the posterior end of an EPG palate while 9 speakers of standard German produced intervocalic voiceless consonant sequences (stops, fricatives, affricates, and clusters). Past theoretical work suggests that phonation offsets and onsets will show a hysteresis effect, with onsets requiring higher driving pressures than offsets. Of particular interest here is whether the extent of hysteresis differs among stops, fricatives, and obstruent sequences. Data on intraoral pressure change will also be compared with EPG data to explore how supraglottal constrictions affect Pio, and thus, phonation.
MRI-based 3-D vocal tract acoustic analysis of an American English lateral sound
Authors: Zhou Xinhui , Espy-Wilson Carol Y. , Tiede Mark , Boyce Suzanne
Published: May 2008

The lateral sound /l/ in American English involves a complex articulatory configuration that includes one or two lateral channels along the sides of the tongue, and sometimes a lingual-alveolar contact. The acoustic characteristics of /l/ consist of a third formant (F3) that is close in frequency to the F3 of the adjacent vowel(s), but is often considerably weaker in amplitude. Generally, there is relatively weak energy in the F3-F5 region. The articulatory-acoustic relationship is not well understood. Previous studies did not consider the 3-D vocal tract model and the area function extraction was based on some assumed model. In this study, we constructed a 3-D vocal tract geometry based on magnetic resonance images from one subject during sustained production of syllabic dark /l/ (as in "pole"), and performed finite-element analysis. The harmonic analysis showed that the frequency response of the 3-D vocal tract is comparable in many ways to the spectrum of the acoustic signal, suggesting good agreement between the actual and reconstructed vocal tracts. A pole-zero pair is found in F3-F4 region, which may explain the weak energy level in this frequency region. Application of the 3-D wave propagation property to vocal tract area function extraction will also be discussed. [Research supported by NIH.]
Behavioral and physiological correlates of language preference
Authors: Sundara Megha , Kitamura Christine , Nazzi Thierry
Published: May 2008

With increasing experience listening to language, infants' sensitivity to the patterns of their native language becomes more specialized. In monolingual, hearing infants, this tuning-in into the native language has been demonstrated in an elegant experiment. Hayashi et al. (2001) tested Japanese-learning infants between 4 and 14 months on their preference for listening to Japanese when compared to English. Not surprisingly, Japanese-learning infants preferred to listen to Japanese over English. Critically, the magnitude of this native language preference increased linearly from 4- to 14-months. In this study, we replicated and extended Hayashi et al.'s results. We tested 65 Australian-English learning infants aged 3 - 16 months on their preference for Australian-English compared to Japanese sentences. Our results confirm the findings of Hayashi et al.: Australian-English hearing infants' prefer their native language, and this preference increases linearly with age. We also tested preference when the same infants heard Australian-English and German sentences. English and German are rhythmically similar, while differing in segmental characteristics. Results indicate that similar to early language discrimination, rhythmic distance affects the emergence of language preference. We are currently analysing concomitant heart rate measured from these infants when they were listening to native and non-native sentences.
Improvement of speech recognition thresholds by spectral modulation enhancement
Authors: Liu Chang , Eddins David A.
Published: May 2008

Our previous studies have shown that vowel identification in noise was significantly improved by spectral enhancement resulting from modifications in the spectral modulation domain. The present study investigates whether spectral enhancement results in improved speech recognition in background competition. Speech recognition thresholds (SRT) were measured in a long-term speech shaped (LTSS) noise and in multi-talker babble using NU-6 words with and without spectral enhancement for young normal-hearing listeners. Results indicated that SRTs were significantly reduced, by 2.2 dB, in LTSS noise and in babble when speech sounds were spectrally enhanced between 2.0 and 2.5 cycles/octave, while no significant changes in SRTs occurred for enhancement between 1.5 and 2 cycles/octave or between 1.5 and 2.5 cycles/octave. Spectral modulation transfer functions were also measured for each listener. Linear regression analyses showed that SRT improvement was moderately correlated with modulation detection thresholds at a spectral modulation frequency of 0.5 cycles/octave. Thus, it appears that better modulation detection at low spectral modulation frequencies is associated with greater improvement in word recognition in background competition.
Complexity of acoustic-production-based models of speech perception
Authors: Morrison Geoffrey Stewart
Published: May 2008

Discriminant analysis models trained on acoustic vowel production data have been found to have significant correlation with listeners' perception. Two regularised discriminant analysis models were trained on monolingual speakers' vowels. One model was trained on North Central Peninsular Spanish vowel tokens, and the other on Western Canadian English vowel tokens. For each language the model which resulted in the lowest cross-validated classification error rate was close to the least complex model possible, i.e., close to linear discriminant analysis using the variances of each acoustic variable but not the covariances between variables. In order to make cross-language vowel perception predictions the Spanish model was used to classify English vowel tokens and the English model was used to classify Spanish vowel tokens. Results suggest that monolingual North Central Peninsular Spanish listeners would assimilate most tokens of Western Canadian English /i/ and /I/ to Spanish /i/ and /e/ respectively, and thus for this combination of dialects, Spanish-speaking learners of English would not be expected to have difficulty with the English /i/-/I/ contrast.
Lexical analysis of spoken word recognition errors
Authors: Felty Robert A. , Buchwald Adam , Pisoni David B.
Published: May 2008

In speech perception and spoken word recognition, a lexical "neighbor" of a target word is a phonetically similar word that competes with the target during lexical access. A commonly-used definition is that neighbors differ from one another by a single segment. While this basic definition accounts for many results of lexical decision and word recognition tasks among monosyllabic words, it also suggests that approximately half of the words in the English lexicon are hermits (words without neighbors). To generate a more inclusive definition of neighbor, we created a representative sample of the lexicon (N=1428) to examine spoken word recognition errors, and we used the incorrectly selected competitors as a means of indexing "neighbor" status. Analysis of over 15,000 errors reveals several patterns: (1) Errors tend to be of higher frequency than the target word; (2) Less than 1/3 of the errors were neighbors according to the traditional definition of neighborhood density; and (3) Errors differed in phonetic similarity more as the S/N ratio decreased. We use these data to test several alternative definitions of "neighbor" and their ability to predict actual word recognition errors. [Work supported by NIH-NIDCD R01 00111 and T32 00012]
Articulatory constaints on coarticulation in fricatives as a function of tongue involvement
Authors: Gelfer Carole E. , Bell-Berti Fredericka
Published: May 2008

Numerous studies have shown coarticulatory effects of vowel rounding on the spectra of sibilants. However, the extent to which the tongue contributes to coarticulation is not clear because most studies have used only fricatives whose constriction is formed with the tongue. This study examines the effects of vowel environment on coarticulation in fricatives under two conditions: when the constriction is formed with the tongue (i.e., [s]) and when it is not (i.e., [f]), paired with the English vowels occurring at the extremes of the vowel quadrilateral. Preliminary results for adult native speakers of American English suggest that in the absence of tongue constraint (i.e., [f]), there is a greater effect of vowel context on the fricative spectrum. This result reinforces the importance of considering the freedom of an articulator to anticipate an upcoming gesture when examining the extent of coarticulation.
Prosodic effects on articulatory coordination in initial consonant clusters in German
Authors: Bombien Lasse , Mooshammer Christine , Hoole Phil , Kuehnert Barbara
Published: May 2008

This study examines how articulatory coordination in heterorganic initial consonant clusters is modulated by prosodic condition. Extending the paradigm of articulatory strengthening at domain edges to clusters, we provide EPG data of 7 speakers as well as EMA data of two speakers including domain-initial clusters (/kl/, /kn/ and /sk/) in different prosodic positions, varying the strength of the preceding boundary and the position of lexical stress. (e.g. 'Claudia vs. Klau'sur, i.e. stressed vs. unstressed target cluster). The results show that C1 was consistently lengthened at higher boundaries, but only if the cluster was preceded by a clear pause. C2 was only weakly and inconsistently affected. There were no effects on the spatial domain at all. No consistent effects of lexical stress were found for either C1 or C2. Regarding overlap of C1 and C2 there was a tendency, albeit quite weak, in the direction of more overlap at the lower boundary levels and in unstressed condition. However, differences in timing between segmentally different clusters were consistent and much larger than boundary and stress effects. Especially for /kl/ vs. /kn/ we find that the lateral's timing to /k/ is much closer than the nasal's.
A comparison of task and non-task related variability in speech production and acoustics, with implications to speech perception
Authors: Iskarous Khalil
Published: May 2008

Task Dynamics provides a way of testing whether production goals are acoustic or articulatory. According to this theory, during the production of a segment, the vocal tract can be divided into locations where a task is specified and locations where no task is specified. The goal is for articulators to synergetically achieve the constriction in the task location. Articulatory variability in the non-task locations is permitted due to overlap. However, articulatory activity in both task and non-task locations affects the area function and acoustic output. Therefore it is possible that an articulatory synergy stabilizes an articulatory task variable, without stabilizing the acoustics, evidence that the goal is articulatory. An experiment on the articulation and acoustics of /Vd/ in Ameican English by 26 subjects, using the Wisconsin Xray Microbeam database, shows that there is a synergy between jaw and tongue tip that explains 79% of the variability in articulator locations. This synergy stabilizes the position of the tongue tip in the alveolar region. But the formant transitions and bursts are highly variable, since the back of the tongue and jaw assume positions consistent with the preceding vowel-evidence that the goal is articulatory (Funded by NIH DC-02717).
Why words do not have a psychological alphabet
Authors: Port Robert F.
Published: May 2008

Linguists and psychologists share a powerful intuition that the psychological form of language (in memory) employs letter-like units for spelling words and any other linguistic material. However evidence accumulating over the decades shows that memory for linguistic material actually consists of continuous-time representations containing much more information than we thought, plus there are episodic representations with much redundancy. So Liberman's /di/ and /du/ share nothing in their representation. There need not be an abstract /d/ in the memory representations of language. Our intuition that a letter-like representation is necessary for speech perception and production turns out to be shared only with literate people. Because we cultivate our reading and writing skills, we bias our brains (and consciousness) to model speech using something like letters (e.g, phones) - either from an orthographic or a technical alphabet. So our conscious experience of language is shaped by our cultural tradition of training children to hear speech as letters and letters as speech - all to exploit the technology of literacy. When we can overcome this education-based bias toward phones and phonemes, we will discover the phonemic emperor has no supporting evidence. Linguistic material in memory is richly detailed - relative to what an alphabet represents.
Robust array pattern synthesis with uncertain manifold vector
Authors: Yan Shefeng
Published: May 2008

The knowledge of the array manifold vectors of an acoustic array can be imprecise, which is often the case in practice. This may cause undesirably high sidelobes for a nominal optimal beamformer where the array manifold vectors are assumed to be known exactly. Although the norm constraint on beamformer weights can be imposed to improve the robustness of the optimal beamformer, it is not clear how to choose the optimal constrained parameter based on the known level of uncertainty of the array manifold vectors. A pattern synthesis approach to arbitrary arrays with robustness against array manifold vectors errors is developed. Our technique optimizes the worst-case performance by minimizing the worst-case sidelobe level while maintaining a distortionless response to the worst-case signal steering vector. The parameters can be optimally chosen based on the uncertainty of the array manifold vector. The robust beamformer problem is shown to be convex, which can be efficiently solved using second-order cone programming. A simple lower bound on how much worse the robust optimal beamformer will be compared to the nominal one is also derived. Computer simulations show better performance of the proposed robust beamformer.
Quantitative Ultrasonics for Inclusion and Pore Characterization of Steel Billets
Authors: Kananen Ville , Eskelinen Joona , Hæggström Edward
Published: May 2008

We present ultrasonic quantitative inclusion and pore characterization in bearing steel 100Cr6. A 9.5MHz focused transducer (14cm focal length, 6.3MHz bandwidth) scanned across the top surface of immersed 22*12*6cm3 production samples (8pcs). Automatic pre-processing was employed to detect inclusions in samples. Recorded RF-data were analyzed. Continuous wavelet transform and cross-correlation were applied to measured and registered RF-signals from known (verified by SEM) inclusions and pores. This allowed characterizing the echoes by shape from wavelet coefficients (WC) and cross-correlation coefficients: the echo is a superposition of the reflection from the inclusion front and back surface, whereas pores exhibit no back surface echo due to their large acoustic impedance mismatch. Fourier transform allows characterizing echo RF-signals by frequency content. Dissimilarities -signal phase and WCs- in echo characteristics between different inclusion and pore classes allows quantitative inclusion and pore characterization. We discriminate three classes: oxide-inclusions (aluminium-oxides, calcium-aluminates), sulphides (manganese-sulphide), and pores. We also estimate inclusion size, position, and orientation. Rolled (reduction ratio 4 and 10) and unrolled production samples are characterized. The instrument functionality was validated by blind tests using SEM. Inclusion distributions in different classes of steel 100Cr6 and classification probabilities are presented. Our software saves sample preparation and image analysis work.
Wavelet threshold enhancement by an energetic characterization of ultrasonic signal Ndt analysis
Authors: Bettayeb Fairouz
Published: May 2008

In ultrasonic NDE of industrial components, the visibility of flaw echoes is corrupted by noise due to multiple scattering. Grain boundaries can reach the size of the same order of magnitude than discontinuities to be detected, becoming scatters of ultrasonic noise and could be confused with defect indications. Many studies have been conducted on the use of the wavelet theory for ultrasonic signal de-noising, but nothing has been done on the structural noise features and its analyzing wavelet function. In the framework of the automation of the ultrasonic signal analysis project, we have followed the exploration of the wavelet theory, from the continuous transforms to the discrete ones, and the experiments give us some ambivalent results. So for a best threshold control, our idea was directed to the investigation of the noise analyzing function. In this work the noise features were extracted by an energetic smoothing algorithm that allows the exploration of the noise analyzing function; by which the random nature of the noise in the spatial domain is bypassed. The energetic characterization of the noise and the defects allows an improved filtering process. The new smoothing algorithm performs an accurate signal reconstruction in an interesting computing time.
Time Reversal Acoustic focusing with random reverberator
Authors: Fillinger Laurent , Sutin Alexander , Sarvazyan Armen
Published: May 2008

Time Reversal Acoustic (TRA) focusing system based on an external reverberator can provide good focusing with minimum side lobes even with a few transducers. The focusing ability of such system can be increased using reverberator with rough boundaries or by adding internal random scatterers. The experiments were conducted with a reverberator made of a polyethylene bottle filled with water and a single piezoceramic disk attached externally to its wall. Experiments demonstrated that inserting in the bottle random hard scatterers or altering of the bottle surface significantly decreases the size of the focused spot and the level of side lobes. The new pseudo-impulse method of TRA focusing allowed suppressing piezotransducer resonances and provided formation of short wide band signals. The ability of such TRA focusing system based on random reverberator to form simultaneously multiple focuses and produce focal spots of the complex shape has been demonstrated. The application of binary radiation regime led to several fold increasing of the amplitude of the focal spot while the focal structure practically was not affected. Applications of such random focusing system for medical imaging and HIFU treatment is discussed.
Isolation of backscattering resonances of a thin spherical shell using iterative time reversal
Authors: Waters Zachary J. , Dzikowicz Benjamin R. , Holt R. Glynn , Roy Ronald A.
Published: May 2008

The backscattering spectrum of thin spherical shells show resonance peaks due to several different physical processes including high frequency Lamb wave excitation and low frequency modal ringing [Kaduchak et al., J. Acoust. Soc. Am. 97, 2699-2708 (1995)]. These different processes can be isolated in both time and frequency by using simulated iterative time reversal. This is accomplished by windowing in the time domain and/or filtering in the frequency domain. Iterative time reversal techniques developed for buried target detection [Waters et al., J. Acoust. Soc. Am. 122, 3023 (2007)] are applied to the partial wave series solution for the backscattering of plane acoustic waves by a thin-walled spherical shell. Tank experiments are performed to verify theoretical results. Targets loaded with both water and sediment are considered. Understanding the relationship between the time reversal window's size/position and the dominant target scattering mechanisms is key to the development of time reversal as a detection and identification technique. [Work supported by The Office of Naval Research.]
The Decomposition of the Time Reversal Operator with virtual transducers
Authors: Robert Jean-Luc , Fink Mathias
Published: May 2008

The FDORT method (French acronym for Decomposition Of the Time Reversal Operator using Focused beams) is a variant of the DORT method using focused transmits instead of single element transmits. An intuitive interpretation of the method is presented here. It is shown that the FDORT method is equivalent to a DORT method with two different arrays: the actual array and a virtual array whose transducers are located at the foci of the transmits. By changing the focal depth, it is possible to change the position of the virtual array and thus obtain different information. An application to aberration correction in a far field phase screen model will be presented.
Numerical modeling of the effects of finite size transducers for time reversal acoustics in solid media
Authors: Griffa Michele , Anderson Brian E. , Johnson Paul A.
Published: May 2008

Time Reversal Acoustics (TRA) has been shown to be very robust not only in fluids but also in solid bounded media. The most relevant limitations to the Time Reversal Process (TRP) in solid specimens are the co-existence of several propagation modes, mode conversion at each interface (inhomogeneities or boundaries), attenuation mechanisms and the multidimensional nature of the propagating wave fields. Additional limitations arise in practical applications, for example for Non Destructive Evaluation purposes, when the Time Reversal Mirror (TRM) piezoelectric transducers are usually attached to the surface of the solid. We have investigated the role of the finite size of the TRM transducers and their sensitivity to only certain components of the incident wave fields in the TRP when they are attached to the surface of the sample under study. We have developed a theoretical analysis and performed numerical simulations and laboratory experiments in order to examine the robustness of TRA in solid media, including where the TRM is composed of finite size elements attached to the specimen surface. The results lead to useful information about the efficiency of the TRP as well as the optimization of the TRM setup in terms of transducer size.
Acoustic signal processing methods for detecting intrusions and threats in the battlespace
Authors: Ferguson Brian G. , Lo Kam W.
Published: May 2008

The processing of acoustic sensor data enables the detection, classification, localization and tracking of intrusions and threats in the battlespace. Initially, passive acoustic signal processing methods that are used in unattended ground sensor networks and onboard uninhabited aerial vehicles are reviewed. These methods process radiated noise (acoustic signature) data generated by sources of military interest and extract tactical information on air and ground vehicles as well as direct (rifle) and indirect (artillery/mortar) fire weapons. Examples of applying various passive acoustic signal processing methods to real sensor data collected during field experiments are presented. The tactical parameter estimates derived from these acoustic methods are then compared with ground truth data. Next, the application of active sonar signal processing to the automatic detection and tracking of a fast inshore watercraft in a cluttered harbor environment is demonstrated using real data. The air bubbles associated with wakes from high-speed surface craft are highly reflective of incident high frequency sonar signal transmissions. Finally, various high frequency active sonar methods that use both real and synthetic apertures to image sea mines are reviewed and demonstrated.
Automated Identification of Vehicles using Acoustic Signal Processing
Authors: Evans Naoko , Chesmore David
Published: May 2008

Automated identification of unauthorised intruding vehicles approaching protected infrastructure is becoming increasingly important for security purposes. This three-year project, which is now in its second year, aims to develop a real-time acoustic vehicle type recognition system that will be predominantly composed of three main parts; acoustic signal pre-processing, feature extraction, and decision making (or classification). The main study area covers various signal processing techniques in time, time-frequency and potentially frequency domains with signal classification implemented using a range of artificial intelligence techniques such as artificial neural networks. So far the focus has been on time domain signal processing and neural network classification. Whilst the work is at an early stage, the time domain methods such as Time Domain Signal Coding (TDSC) and Co-Occurrence Matrix combined with neural networks have already shown some promise. The presentation will introduce the project, describe methodologies involved as well as the results to date for the novel acoustic identification of categories of vehicles.
Active sonar clutter and auralization
Authors: Abraham Douglas
Published: May 2008

Target-like false alarms generically termed clutter are the primary hindrance to active sonar in shallow water operational areas. Clutter can arise from a myriad of sources with geologic, biologic and anthropogenic origin. The clutter-source echoes are often determined by automatic signal processing to be target-like and therefore potentially of interest. These numerous false alarms consume either the sonar operator's time or flood automated data and information processing algorithms. Aural analysis of clutter echoes (auralization) can increase active sonar performance through improved operator or algorithmic classification. An overview of active sonar clutter is presented with a focus on the role of auralization for clutter reduction. [Supported by the Office of Naval Research Code 321US under contract number N0001407C0092]
Auditory models and nonlinear filterbanks in underwater auralization
Authors: Bleeck Stefan , Fox Paul D. , White Paul R. , O'Meara Niamh
Published: May 2008

Mammals like dolphins and humans have the ability to distinguish between different objects by listening to their scattered signals. We explore this phenomenon by evaluating the "Auditory Image Model" (AIM), a biologically inspired model of the human auditory system from the outer ear up to central processing. AIM aims to simulate the spectral analysis of the basilar membrane, the neural encoding and the temporal integration performed by the auditory system. Simulated scattered signals from the same object objects of different sizes and different objects of same size subjected to an incident pulse were analysed numerically with AIM, simulating the response of the human auditory system. The resulting neuronal activity patterns were analysed in two independent dimensions using the filter centre frequency and the relative timing intervals of the responses. The results are interpreted globally as reflecting the size and the shape/properties of the object respectively. We show for a series of calibration stimuli that the model can distinguish between same objects of different size and different objects of the same size. We also discuss how a nonlinear model of the basilar membrane, performing a Gammachirp/Mellin transformation, may act as a possible feature extraction tool for classification methods
Modeling the mechanism and neural substrate for aural categorization of sonar echoes
Authors: Summers Jason E. , Gaumond Charles F. , Brock Derek , Baer Ralph N.
Published: May 2008

Previously, human perception of impulsive active-sonar echoes was investigated through paired-comparison ratings and multidimensional scaling (MDS). In the resulting MDS configuration, stimuli formed clusters representing aurally distinct categories. An interpretation is presented which suggests that dissimilarity judgments reflect separate processes for within- and between- category comparisons. The process of categorization is not based on decision boundaries in a low- dimensional space of ordinal-scale perceptual features, while within-category judgments do reflect such features. A class-specific paradigm seems appropriate as a model of human categorization: signals are compared to category archetypes, each described by a set of features that may be unique to that category. Regardless of the specific mechanism, listeners must carry out categorization on a particular signal representation: the neural substrate of the process. The suitability of various temporal, spectral, and time-frequency signal representations are investigated through observing categories formed by hierarchical clustering. A signal-processing model of the spectrotemporal receptive fields of the auditory cortex and the processing of the auditory periphery [T. Chi et al., J. Acoust. Soc. Am. 118, 887-906 (2005)] is shown to yield good agreement with human categorization. Techniques for feature selection from this representation are discussed. [Work supported by ONR.]
Automatic classification of vocalizations with Gaussian Mixture Models and Hidden Markov Models
Authors: Brown Judith C. , Smaragdis Paris
Published: May 2008

The automatic classification of marine mammal sounds is very attractive as a means of assessing massive quantities of recorded data, freeing humans and offering rigorous and consistent output. Calculations on a set of vocalizations of Northern Resident killer whales using Dynamic Time Warping have been reported recently. [Brown, J. C., and P.J.O. Miller, ''Automatic classification of killer whale vocalizations using dynamic time warping,'' J. Acoust. Soc. Am. 122, 1201-1207, (2007).] Since this method requires the time-consuming pre-processing measurement of the frequency contours, we have explored the use of Gaussian Mixture Models (GMM) and Hidden Markov Models (HMM). These methods can be applied directly to time-frequency decompositions of the recorded signals. Calculations have been made on a set of 75 calls previously classified perceptually into 7 call types. Preliminary results give an agreement of roughly 85% agreement with the perceptual classification for the GMM and over 90% for an HMM.
Calibration of vector sensors
Authors: Clark Joseph A.
Published: May 2008

Vector sensors that combine a hydrophone and a triaxial arrangement of accelerometers in a neutrally buoyant package are currently being used for underwater radiated noise measurements and other applications. Precise amplitude and phase calibration is required to obtain high quality measurements. A basic procedure that has been used successfully to calibrate measured radiated noise spectra in one-third-octave and narrowband formats will be described. Results of validation experiments that compared vector sensor measurements with other reference data will be presented. An iterative calibration scheme for improving the performance of a vector sensor employed as part of an active sonar system will also be presented.
Calibration of broadband active acoustic systems using a single standard spherical target
Authors: Stanton Timothy K. , Chu Dezhang
Published: May 2008

When calibrating a broadband active acoustic system with a single standard target such as a sphere, the inherent resonances associated with the scattering by the sphere pose a significant challenge. In this research, a method is developed which completely eliminates the source of resonances through isolating and exploiting the echo from the front interface of a sphere. This echo is relatively insensitive to frequency over a wide range of frequencies, lacking resonances, and relatively insensitive to small changes in material properties and, in the case of spherical shells, shell thickness. The research builds upon the concept of using this echo for calibration in the work of Dragonette et al. (J. Acoust. Soc. Am. 69, 1186-1189 (1981)). This current work generalizes that of Dragonette by 1) incorporating a pulse compression technique to significantly improve the ability to resolve the echo, and 2) rigorously accounting for the scattering physics of the echo so that the technique is applicable over a wide range of frequencies and material properties of the sphere. The utility of the new approach is illustrated through application to data collected at sea with an air-filled aluminum spherical shell and long broadband chirp signals (30-105 kHz).
Low frequency hydrophone calibration with using tensometric pressure sensor
Authors: Isaev Alexander , Shchelkunov Alexander
Published: May 2008

Usually when calibrating a hydrophone in an acoustic coupler the piezoelectric hydrophones use an auxiliary transducer. Widely applicable reciprocity calibration is high-ly accurate, but difficult in realization and laborious. The method of comparison with a reference transducer is more simple and quick, but less accurate. In the paper the method of low frequency hydrophone calibration using the auxiliary transducer with a flat frequency response up to 3 kHz is considered. The auxiliary transducer is calibrated accurately by changing the water column in the acoustic coupler. It finally allows us to calibrate measuring hydrophones more accurately too. The measuring equipment on the basis of tensometric pressure sensor type MPX 5010 is considered.
Estimating the frequency dependent behavior of marine sediment sound speeds using low frequency aircraft sound
Authors: Amiri-Simkooei Alireza , Snellen Mirjam , Simons Dick G. , Buckingham Michael
Published: May 2008

For investigating the dispersion behavior of sediment sound speeds, broadband sound speed measurements are required. Sediment sound speed dispersion models predict the largest sound speed variations typically at low frequencies. Aircraft fly-over noise acquired on receivers placed in sediment proved to be a promising approach towards broadband low-frequency measurements. Since the magnitude of the Doppler-shift depends on sound speed at the receiver position, the observed Doppler-shift can be used to derive the sound speed. We propose a new approach using the entire time series instead of employing only the two observed frequencies at approaching and departing. It is based on a model for received signals, accounting for the Doppler-shifted frequency. By maximizing the match between modeled and measured time series as a function of sound speed and frequency in a least-squares framework, estimates of the frequency-dependent sound speed are obtained. The method is applied to data acquired at receivers placed in air, water and sediment. Statistical tests indicate that the marine sediment sound speed depends indeed on frequency, i.e. sound speed decreases significantly below 300 Hz. A comparison is made with a modified viscous fluid model from which realistic values for the geotechnical parameters of the considered sediment were obtained.
The influence of topography on sidescan sonar images
Authors: Bürk Dietmar , Klaucke Ingo
Published: May 2008

The backscattering signal on sidescan sonar images is to a large degree dependent on the incident angle of the acoustic beam onto the seafloor. As sidescan sonar systems are often used for mapping seafloor lithologies, it is necessary to reduce or even remove the effect of different backscattering strengths caused by varying incidence angles. This study evaluates the influence of seafloor morphology on the acoustic backscattering signal of the deep-towed IFM-GEOMAR DTS-1 sidescan sonar system. Data used are from the Pacific continental slope offshore Nicaragua in a water depth between 800 and 2400 metres. There authigenic carbonate patches formed by cold fluid venting are imaged with a high backscattering level. The carbonates are often located on top or on the flanks of mound structures with a strong morphology. The specific DTS-1 backscattering function is determined on normal, uniform seafloor sediment, and then applied in a new processing algorithm to the raw data of two test areas. The change in amplitude strength when considering seafloor morphology is calculated. The topographic influence on the backscattering signal can be quite significant when imaging mound structures. Nevertheless the high backscatter on mounds is not completely removed, leading to the conclusion that it originates from a different seafloor lithology and roughness.
Use of dual methods to infer methane bubble populations in gassy sediments: Inversion of combination-frequency data
Authors: Mantouka Agni , Leighton Timothy G. , Robb Gary B. , Best Angus I. , Dix Justin K. , Klusek Zygmunt , White Paul R.
Published: May 2008

Bubbles can dramatically change the acoustic properties of their host medium even if they are present in very small amounts. This paper describes the combination-frequency component of tank and field measurements taken using a device which measures bubbles in marine sediments using multiple acoustic techniques (allowing the results of the various techniques to be compared). The combination-frequency method uses the nonlinear scattering property of bubbles when insonified by two primary frequencies. For low void fractions, there is a monotonic relationship between the scattered field and the population of bubbles resonant at either of the primary frequencies or combination of these and/or their subharmonics. This principle is used to infer the bubble size distribution. In contrast to the case of gas bubbles in water, in marine sediments the shear properties of the host medium must be incorporated into the model for the bubble dynamics and a new model for this is presented. This model is then inverted to obtain the bubble size distribution. The predictions of this method were compared with the method of inversion of propagation data (detailed in a companion paper), obtained from in situ experiments on the South coast of England.
Comparisons of Biot and grain-shearing theories: sound speed, attenuation and acoustic impedance
Authors: Hefner Brian T. , Williams Kevin L.
Published: May 2008

The comparison of sediment sound speed and attenuation measurements to predictions has been the primary method used to test Biot theory and the grain-shearing model. Examples of data/model comparisons will be shown. Subsequent refinements made to these models result in similar predictions for sound speed and attenuation. However, the underlying physics is substantially different suggesting other, more indirect means for discriminating between sediment propagation theories. One technique that has received recent attention is the measurement of forward scattering from the sediment interface. Model predictions of these measurements depend not only the sound speed and attenuation, but also on the acoustic impedance of the medium. Examination of the physics incorporated into Biot Theory shows that the 3effective density2 seen by the acoustic wave is lower than the bulk density, thus lowering the acoustic impedance. This results in a difference in the predicted flat surface reflection coefficient for Biot-type models as compared to grain-shearing models. The flat surface reflection coefficients derived from experiment will be compared with predictions using the Biot model and the viscosity grain shearing (VGS) model for a sand sediment. The validity of obtaining reflection coefficients using forward scattering from rough surfaces will also be discussed. [Work supported by ONR.]
Geoacoustic Inversion Based on a Vector Hydrophone Array
Authors: Li Fenghua , Zhang Renhe
Published: May 2008

Vector sensor has attracted much attention in recent years. However, there are few papers involving in geoacoustic inversion from vector sensor. In this research, a geoacoustic inversion scheme employing a vector hydrophone array has been developed based on the fact that vector hydrophone can provide more acoustic field information than traditional pressure hydrophones. The inversion scheme is the combination of the Matched Field Processing and the difference of transmission losses between pressure and velocity. The advantages of this method are that it can decrease the uncertainty of the inverted sediment sound speed and the inversion of the sediment attenuation is independent on the source level. [Work supported by the National Natural Science Foundation of China under Grand No. 10574136].
Computer modelling and simulation of sound field in 24 rectangular concert halls
Authors: Klosak Andrzej K.
Published: May 2008

Extensive acoustics computer simulations has been made using Odeon computer simulation software. From 300 to 850 measurements positions have been analysed in 24 rectangular rooms representing "shoe-box" type concert halls with volumes of 8 000m3, 12 000m3 and 16 000m. In total 14 000 receiver positions have been analysed. For each receiver position eight objective measures have been calculated, in particular Reverberation Time (T30), Early Decay Time (EDT), Clarity (C80), Strength (G, Gearly, Glate), Early Lateral Energy Fraction (LF80) and Late Lateral Strength (GLL). Most of measures have been calculated in six octave bands from 125Hz to 4000Hz. Extensive amount of generated data required developing of new methods for processing, comparing and graphical presentation of results. Those methods together with description of modelling and simulation procedures are described in this paper.
Improvement of acoustic conditions in a historical interior by means of a DSP-controlled sound-reinforcement system
Authors: Fidecki Tadeusz , Miskiewicz Andrzej , Zera Jan
Published: May 2008

Stringent building conservation requirements in historical interiors pose substantial limitations in acoustical treatment and sound reinforcement systems used to secure proper sound quality. This presentation discusses the means undertaken to improve the acoustic conditions in the historic Great Ballroom of the Royal Castle in Warsaw. Originally, the room was too reverberant (T30 = 2.9 s at 500 Hz) what resulted in a lack of clarity of performed music and poor speech intelligibility (STI < 0.3). A precise laser scan of the interior was made to obtain input data for a computer acoustic model of the room. This model was used for selection of a DSP-controlled sound reinforcement system to improve listening conditions for speech and music. [Work supported by the Polish Ministry of Science and Higher Education, grant No. R17 004 02].
Open-air theatre in the centre of the city: Acoustic design and noise environment control
Authors: Barkas Nicolaos
Published: May 2008

The municipal open-air Garden Theatre of Thessaloniki has for decades been located in the biggest urban park of the city next to a busy crossroads, where five major traffic roads meet. The intensification of traffic noise over the years led to the degradation of its use. In 1997, the organisation of the Cultural Capital of Europe served as a springboard for a study conducted by the author on redesigning the theatre. The design comprised a variety of arrangements, such as the rotation of the auditorium according to the results of the noise environment study, the choice of a closed plan in the type of the Greek-Roman Odeion, the sinking of the theatre space and the construction of barriers and shades. Various problems (such as archaeological findings, existence of big trees inside the auditorium, high level of underground water) and budget cuts during the design and construction, led to restricted execution of the planned architectural interventions. This paper deals with the design parameters that optimise acoustic function and maximise sound protection in an urban, open-air theatre and includes an analysis of the theatre's initial state, acoustic proposals and an assessment of the final applications.
New acoustic test chambers at the University of Palermo
Authors: Gullo Marco , La Pica Armando , Rodono' Giuseppe , Vinci Vincenzo , Conti Vincenzo
Published: May 2008

Acoustic test chambers at the University of Palermo have been completed after a design optimization of existent building structures. A unique building houses five reverberation chambers, differently coupled each other in order to achieve a large flexibility on testing procedures, and offices for the staff. Main measurements offered to national and international standards include determination of sound power, sound insulation and sound absorption. Reverberation chambers present peculiar geometries in order to achieve the desidered sound fields. Chambers structure and layout within the whole building, housing all the acoustic facilities, has been designed in order to achieve strong sound insulation requirements. The present work describes design solutions and reportes preliminary results from a large, still running, validation in order to characterize the chamber acoustic behaviour. Design targets and objective achievements are listed and commented.