bluuebunny/crossref_metadata_2025 huggingface dataset:
Categorical and non-categorical perception of speech: Behavioural and neural evidence
Authors: Rogers Jack C. , Davis Matthew H.
Published: May 2008

What effects do within- and between-category variations have on the perception of speech? Using audio-morphing and the "Straight" channel vocoder (Kawahara, 2004), we produced 320 high-quality phonetic continua varying in place, manner and voicing including word/word (blade/glade), word/pseudo (blouse/glouse), pseudo/word (bown/gown) and pseudo/pseudo (blem/glem) pairs. A 2AFC task confirmed the category boundary shift for word/pseudo and pseudo/word pairs (Ganong, 1980), equivalent for onset (bench/gench) and offset (flad/flag) pairs. This suggests that lexical influences on categorical perception are not produced on-line but rather occur post-perceptually, consistent with top-down effects. Sensitivity to within- and between-category phonological variation was investigated using sparse fMRI in a paired auditory repetition priming paradigm. Minimal pairs (48 across the 4 stimulus groups) were presented to participants who listened in the context of a semantic monitoring task. Between-category pairs with a phonological change produced a greater neural response compared to within-category same pairs with the same magnitude of acoustic difference. This response to phonologically different pairs provides a neural correlate of categorical perception in left middle temporal, inferior frontal and pre-central regions. These responses in inferior frontal regions may contribute towards top-down influences on categorical perception of speech (cf Ganong Effect).
Distinguishing Place of Consonant Articulation using the Aurora System
Authors: Yunusova Yana , Stanley Jeff , Green Jordan R.
Published: May 2008

The goal of this project is to determine the effect of bite-block and speaking rate manipulation on lingual targets for consonants using a recently developed Aurora, a 3-D electromagnetic movement tracking system (NDI). Bite-block and speaking rate manipulations are common intervention techniques with speakers with dysarthria and apraxia of speech. Therefore, understanding their effect on consonant target regions is essential for predicting the outcomes of articulatory training in these clinical populations. In this project, articulatory positions of two sensors on the tongue tip and dorsum will be recorded independent of the head. Stops /t, k/ and fricatives /s, sh/ will be embedded in aCa syllables. A bite block condition will be used to eliminate jaw contribution to tongue movements. The location and size of articulatory regions associated with each consonant will be compared in bite block and no-block conditions. Additionally, the rate effect on the location and size of the consonant articulatory regions will be examined. Potential clinical implication of the finding on articulatory intervention will be considered.
Time-frequency detection of stridence in fricatives and affricates
Authors: Jovicic Slobodan , Punisic Silvana , Saric Zoran
Published: May 2008

As wheezes in abnormal breath sounds observed in patients with obstructive pulmonary diseases, the stridence in voice is manifested as excessively sharp, conspicuous, usually habitual hiss that is especially distinct with whispering. This paper reviews the articulator and acoustics features of stridence in unvoiced fricatives and affricates, and presents an algorithm for detection of stridence. Detection of stridence was based on: time-frequency representation by FFT power spectra, time-frequency representation by AR-Burg power spectra, and power trajectory of signals in characteristic frequency bands. Many features are extracted from this analysis, as: the local power spectra maximum to average surrounding power ratio, the correlation coefficient between spectral and power maxima in signal, the spectral power slope in selected frequency band, spectral entropy in selected frequency band, and phoneme duration. The extracted set of features is input to the nonlinear classificator that decides about stridence in voice and the level of pathology. The algorithm was tested with speech database of normal and pathology voices. The speakers were both sex and the different ages. The results of automatic stridence detection showed high level of coincidence with the judgment of speech therapists.
Acquisition of the production of 'new' and 'similar' vowels: the case of /u/ and /y/ in French by Japanese-speaking learners
Authors: Kamiyama Takeki
Published: May 2008

French /y/ (F2/F3 close around 2000 Hz for males) does not have an equivalent phoneme in Japanese and English, whereas /u/ (F1/F2 close < 1000 Hz) has a phonemic counterpart (high back) in both Japanese and English, but its phonetic realization is different from French /u/, with a higher F2. Flege (1987) found out that it was easier for American English speakers to acquire a native-like production of French /y/ ("new" phone) than that of /u/ ("similar" phone). Our recording of two groups of adult Japanese-speaking learners of French (JLF) shows a similar tendency. We measured the formants of isolated vowels embedded in a carrier sentence read 3 times by JLFs. In the first group, consisting of 3 elementary learners who volunteered for the task, 2 learners pronounced /y/ with close F2/F3, but none of them produced a low F2 (< 1000 Hz) for /u/. In the second group, consisting of 50 JLFs in 4 different classes and levels (elementary to upper intermediate), only 4 of them, who had all lived in a French-speaking country except one, produced /u/ with a low F2 (< 1000 Hz), whereas a dozen of them pronounced /y/ with close F2/F3.
Adapting second language phonemic perception training to common instructional situations: A progress report
Authors: Sawallis Thomas R. , Townley Michael W.
Published: May 2008

Although current L2 pedagogy de-emphasizes phoneme-level pronunciation training, laboratory experiments demonstrate benefits from training non-natives in perception of difficult target-language phonemic contrasts. Specifically, evidence shows that: learners' perceptual performance improves (Jamieson & Morosan, 1986; Flege, 1995), improvements generalize to new talkers and words (Lively, Logan, & Pisoni, 1993), perceptual training triggers production improvements (i.e., without production training, Bradlow et al., 1997), and both perceptual (Lively et al., 1994) and production improvements (Bradlow et al., 1999) are maintained over several months. We are adapting perceptual training methods from such studies for use in common instructional situations, starting with Japanese students learning the English /l-r/ contrast. This paper addresses three practical concerns. First, studies show that the perceptual training needs tokens with multiple kinds of variation. We discuss phonological variation in corpus design, sociolinguistic variation in talker recruitment, and inducement of within-talker variations. Second the training must be usable both independently and in classrooms. We discuss the design of sessions short enough for inclusion as part of daily classroom activities. Third, the training must be computer-controlled. We discuss necessary functions, available programs, and our choice. Finally, we briefly demonstrate the training, and give a sketch of interim results.
Coupled 2D-Fluid-Structure-Acoustic Simulation of the Human Voice
Authors: Link Gerhard , Kaltenbacher Manfred , Doellinger Michael , Lerch Reinhard
Published: May 2008

The human voice is a key factor in social life. If the phonation process is disturbed due to a disease as e.g. hoarseness, communication and social life are strongly affected. Therefore, it is necessary to enhance therapies in order to minimize affliction caused by a disease. There exist different approaches to improve therapies. Experimental field studies of different physical parameters, like acoustic pressure or vocal fold displacements are one possibility. Another promising approach to advance insight into laryngeal dynamics is given by numerical simulations. Due to the growing computing power the complexity of numerical phonation models is steadily increasing and full fluid-structure-acoustic interacting models are now feasible. Therefore, we have developed a two-dimensional numerical model for the human phonation process, which includes the complete fluid-structure-acoustic interaction. As discretization method the finite-element method was applied for all possible three physical fields. The fluid-structure and the structure-acoustic interactions are based on general continuum mechanical principles; the fluid-acoustic interaction is based on Lighthill's acoustic analogy. Therewith, the analysis of all sound mechanisms, which consist of the eddy-induced, the volume-induced, and the mechanical-induced sound can be performed. First simulation results will be presented and discussed.
Analyze effects of the flow on the vocalic reduction and the coarticulation in sequences CV of pharyngal Arabic
Authors: Falek L , Bouferroum O. , Djeradi A.
Published: May 2008

The degree of coarticulation and the vocalic reduction (RV) are indices related to good engine control (Gay 1978). Fowler (1998) explains why locus equation (LE) is used to characterize, at the same time, the place of articulation and the degree of coarticulation between consonants and vowels: a strong slope (m=1) indicates a maximum coarticulation between consonants and vowels (i.e. minimal resistance of the coarticulation), while a weak slope (m=0) indicates absence of coarticulation between consonants and vowels (maximum resistance of the coarticulation). The bond between the degree of coarticulation and the RV can be explained according to the linear relation between F2onset and F2milieu: the modifications of values of F2milieu will affect those of F2onset and consequently those of the slopes. In this study, the analysis of the vocalic reduction and slopes of the equations of locus, carried out on CV (extracts starting from sentences) in standard Arabic pronounced by speakers having different mother tongues (near to Arabic standard and very far away from standard Arabic), and at speed of variable elocution, revealed a vocalic reduction and a variation of the slope of the locus equation, specific to each speaker, who seems to be related to his mother tongue. El Tamimi (2006) carried out a similar study with normal flow, in dialectical Arabic and in French, with normal flow, an influence of the mother tongue showed on the vocalic reduction and the slope of the equation of locus.
Examples of high frequency variability in underwater acoustic systems
Authors: Stein Peter
Published: May 2008

Invited paper for the structured (special) session UW09 High Frequency Variability In this paper we will look at examples of high frequency variability encountered by the author during the design and implementation of underwater acoustic systems over the last 20 years. These systems include those for radiated noise measurements, short baseline tracking, tomographic correction of numerical ocean models, marine mammal detection, and diver detection. The examples will highlight the different physical sources of variability and their effects on system performance. Methods used for mitigating the effects both in the physical design of the sensor system and in the signal processing will also be discussed.
The effects of sediment variability on reflection coefficient measurements
Authors: Isakson Marcia , Chotiros Nicholas P.
Published: May 2008

The statistical distribution of specularly scattered acoustic energy, commonly known as the reflection coefficient, is an important parameter when developing models for shallow water propagation and acoustic communications. The distribution of measured reflection coefficient data from 5 to 50 kHz and 10 to 70 degrees grazing angles was taken from a sea bottom recently perturbed by hurricane off the coast of Florida at the Sediment Acoustic Experiment 2004 (SAX04). The width and shape of the distributions are attributed to varying sediments in the experimental area and interface roughness. These distributions are analyzed to determine the scattering from different types of sediments including sand and mud. The effects of both roughness scattering and sediment variability on the mean value and distribution of the measured reflection coefficient will be explored. [Work sponsored by ONR Ocean Acoustics.]
A solution to the problem of simultaneous classification and localization of underwater objects from their acoustic field
Authors: Mashoshin Andrey I.
Published: May 2008

This paper presents one of the solutions to the problem of simultaneous classification and localization of underwater objects from its acoustical field. It was shown that both problems (classification and localization) have some common features that allow to consider them as one mutual problem which can be solved by maximum likelihood method. The solution takes into account: - the fundamental physical representations of the transmission, propagation, reception of signals, and the measurement of their parameters against the noise background; - the target parameters vector describing features of its noise radiation and motion; - the parameters vector characterizing the observation conditions; - the errors vector of the signal parameter measurements. The theoretical solution is illustrated by solving a relatively simple but practically important problem of classification and ranging of an underwater object from passive underwater acoustic observation data.
Reduced Scale Experiment of Frequency Dependence of Single Spherical Biconcave Acoustic Lens for Ambient Noise Imaging
Authors: Mori Kazuyoshi , Ogasawara Hanako , Nakamura Toshiaki
Published: May 2008

By the numerical analysis results using the Finite Difference Time Domain method in our previous studies, it was supposed that the spherical biconcave lens with an aperture diameter of 2.0 m has sufficient directional resolution (for example, the beam width is 1 deg at 60 kHz) for realizing the Ambient Noise Imaging (ANI) system. In this study, to confirm the directional resolution of the lens in a wide frequency band of 20-100 kHz, we performed a reduced scale experiment of one-fifth space in a water tank. The lens, made of acrylic resin, has an aperture diameter of 400 mm and a radius of curvature of 500 mm. A burst pulse of 25 cycles at 100, 200, 300, and 500 kHz, in which the frequency increases 5 times, was radiated from the sound source to the lens. The results show that the -3 dB area, whose pressure is 3 dB lower than the maximum at the image point, does not overlap each other at 300 and 500 kHz. It is supposed that the lens of 2.0 m aperture has the fine resolution over 60 kHz in the original scale.
On a new approach to numerical modeling of a low-frequency underwater sound in 2 and 3-dimensional oceanic waveguides
Authors: Gulin Oleg E.
Published: May 2008

A new method to compute underwater sound fields in irregular planar waveguides is proposed. It realizes the full two-way propagation approach and exploits an idea of a problem solution dependence on a certain variable parameter that is the position of a boundary of the irregular region. With respect to this parameter for waveguide modes, an initial value problem can be formulated in the horizontal plane that is completely equivalent to the boundary value problem for the original wave equation (Helmholtz equation). This fact allows simulation of sound fields in waveguides based on ordinary differential equations with traditional approximations and for arbitrary source distance from the irregular region and the degree of irregularities. Examples of a simulation for a 2-D irregular waveguide model with an upslope rigid or absorbing penetrable bottom are presented for low frequencies and shallow sea conditions. They illustrate the strong difference between our solution and approximate solutions that arise due to both mode coupling and considerable backscattering within the considered irregular waveguide models
Parametric sonars in searching of buried objects
Authors: Kozaczka Eugeniusz
Published: May 2008

The subject of this paper is the description of usage of the parametric sonar for searching of the objects that are on the surface of the seabed or very close to it. Searching of underwater objects, especially these ones buried in the seabed has a very practical meaning. Presently more often mass destruction weapon is placed in the very difficult way to find it. Moreover searching of the objects of the archaeological character at sea requires usage of devices those have possibility of penetration of sediment which covers the searched object. In this case the most useful of acoustic means are parametric sonars that due to their specific features are good tools for underwater searching. The principle of detection of buried objects is similar to detection in the case of usage of the classical sonars. The dispersion of the sound field enables to track the object and sometimes enables to define the shape of the searched object. The measurement equipment can be connected to the Global Positioning System (GPS) and complementary equipment that is necessary in such kind of investigations. There will be presented experimental results that were obtained during the trials in the Gdansk Bay. Also will be shown the typical images for chosen objects.
Sonar detection of targets buried under seafloor ripple at shallow grazing angles
Authors: Lopes Joseph , Lim Raymond , Dowdy Carrie , Williams Kevin L. , Thorsos Eric
Published: May 2008

This paper summarizes results from modeling and measurement efforts investigating shallow grazing angle reverberation levels from a rippled bottom and subcritical detection of targets buried under such interfaces. The focus of this work is associated with frequencies less than 10 kHz where evanescent transmission is important. Measurements were performed in a 13.7-m deep, 110-m long, 80-m wide test-pool with a 1.5-m layer of sand on the bottom. Rippled contours were artificially formed with the aid of a sand scraper. A parametric sonar that generated difference frequency signals in the 1 to 20 kHz frequency range was placed onto a rail system permitting acquired data to be processed and displayed similar to that of a side scan sonar. The buried target was a solid aluminum cylinder. The seabed roughness was measured to assess ripple fidelity and to estimate the small-scale roughness spectrum which was used in scattering models to calculate the backscattered signal levels from the target and bottom. Acoustic backscatter data obtained for various ripples parameters (wavelengths, heights, orientation, etc.) were compared to model predictions based on perturbation theory. [Work supported by the Office of Naval Research and the Strategic Environmental Research and Development Program, USA].
A novel modelling approach for sound propagation analysis in a multiple scatterer environment
Authors: Van Genechten Bert , Bergen Bart , Pluymers Bert , Vandepitte Dirk , Desmet Wim
Published: May 2008

In the past decades element-based numerical modelling techniques have become a commonly used and invaluable tool for the analysis of acoustic radiation and scattering problems. However, the pollution errors associated with the element discretisation inherent to these methods increase with the increasing size of the problem domain. As a result, the applicability of these methods for radiation and scattering problems in which the source and receiver positions are located far from each other is often prohibited. The Wave Based Method (WBM) is an alternative deterministic prediction method for the analysis of steady-state acoustic problems. It is based on an indirect Trefftz approach in that wave functions, which are exact solutions of the underlying differential equation, are used to describe the dynamic response. The enhanced computational efficiency of the WBM as compared to the element based methods has been shown already for the analysis of both finite and (semi-)infinite acoustic problems. This paper introduces a novel WBM-based methodology to model the acoustic source-receiver transfer path functions in a multiple scatterer environment. A sound propagation validation case illustrates the potential of the proposed approach.
The basis choice and the reconstruction of combined refractive-kinetic inhomogeneities in the problems of ocean acoustic tomography
Authors: Shurup Andrey , Sergeev Sergey , Burov Valentin
Published: May 2008

The characteristics of the acoustical signal in ocean are determined by both the refractive inhomogeneities (the perturbation of sound velocity) and the presence of ocean currents. The methods of acoustical tomography can be applied to the simultaneous reconstruction of both refractive and kinetic inhomogeneities. In this paper the problem of the combined refractive-kinetic inhomogeneites reconstruction by the tomography methods is considered. For the realization of proposed scheme so called band basis consisted of a number of intersected stripes is applied. The advantage of the band basis in tomographic applications is conditioned by the simplicity of solving the direct problem and the possibility of describing all types of inhomogeneities in a unified manner. The comparison of the band basis with the commonly used basis composed of nonoverlapping squares is considered. The results of the reconstruction of model kinetic and combined refractive-kinetic inhomogeneities in band basis are presented. The possibility of complete tomography reconstruction of two-dimensional flows based on the scattering data only is illustrated.
Multiresolution geometrical-acoustics modeling
Authors: Markham Benjamin , Calamia Paul
Published: May 2008

Geometrical-acoustics (GA) modeling techniques assume that surfaces are large relative to the wavelengths of interest. For a given scenario, practitioners typically create a single 3D model with large, flat surfaces that satisfy the assumption over a broad range of frequencies. Such geometric approximations lead to errors in the spatial distribution of the simulated sound field because geometric details that influence reflection and scattering behavior are omitted. To compensate for the approximations, modelers typically estimate scattering coefficients for the surfaces to account stochastically for the actual, wavelength-dependent variations in reflection directionality. A more deterministic approach could consider a series of models with increasing geometric detail, each to be analyzed at a corresponding frequency band for which the requirement of large surface dimensions is satisfied. Thus, to improve broadband spatial accuracy for GA simulations, we propose a multiresolution modeling approach. Using scale model measurements of a corrugated wall, comparisons of our method with non-GA techniques, and some simple listening tests, we will demonstrate that multiresolution geometry provides more spatially accurate results than single-resolution approximations when using GA techniques, and that this improved accuracy is aurally significant.
Ray-tracing prediction of sound-pressure and sound-intensity fields in empty and fitted rooms
Authors: Hodgson Murray , Cousins Owen , Chan Gary , Valeau Vincent
Published: May 2008

A Monte-Carlo ray-tracing model has been adapted to the prediction of sound-pressure and sound-intensity fields in rooms with surfaces of arbitrary surface impedance, and containing parallelepiped obstacles. Phase changes due to propagation distance and wall reflection were accounted for. Diffraction around obstacle edges was modeled by the Unified Theory of Diffraction. The model was also extended to include the out-of-phase secondary sound source of a single-channel, global active-noise-control (ANC) system. The new model was validated in comparison with predictions by reference models (e.g. FEM) and with the results of experiments in an anechoic chamber and in real rooms. It was used to predict the effectiveness of ANC. This paper discusses the development of the new models, the results of the validation tests and ANC predictions.
Acoustical proprieties of light brick walls and its effects on flanking transmission
Authors: Semprini Giovanni , Barbaresi Luca
Published: May 2008

Light brick walls 8-10 cm thick are typical structures frequently used in Italian building constructions as a internal partitions between dwellings and as internal layer of double façade walls. Due to low surface mass and rigid connection to other horizontal and vertical structures, light brick walls are often responsible of high flanking transmission. The simplest acoustic modeling of this structure for the evaluation of sound transmission in buildings, is the approach proposed by the EN 12354 standards, where the brick wall can be considered as a homogeneous structure and main acoustic parameters required are the sound reduction index and the vibration reduction index Kij. The aim of this paper is to analyse results of physical and acoustical properties (sound reduction index, structural reverberation time, radiation efficiency) of a typical 8 cm thick brick wall measured in laboratory testing facility, used as a partition in different test configuration: single layer wall, double brick layer wall with internal thermal layer and as a component of lateral wall, where the Kij index flanking transmission were also evaluated. Experimental results are then compared with theoretical values in order to analyse difference with homogeneous structures.
Methods to control low frequency impact noise in wood-frame construction
Authors: Zeitler Berndt , Nightingale Trevor , King Frances
Published: May 2008

The control of low frequency impact noise is of great importance in Japan and Korea. For impact noise rating, both countries use standardised heavy and soft impactors that inject high levels of low frequency power into a wood-frame floor due to the high force applied and “good” impedance match between the source and the floor. This paper reports on a parametric study designed to confirm the important parameters for controlling low frequency impact noise and how these parameters are affected by changes to construction details. The paper shows that increasing the drive point impedance floor surface while minimising the structural coupling between the gypsum board ceiling and the structural framing (joists) are important elements. Additionally, a well-designed floor topping can be very effective when applied to a suitable floor. The paper presents data to show the relative importance of direct and flanking transmission paths. Furthermore, it is shown that repeated impacts by the Bang Machine physically change the floor assembly and as a consequence resulting impact sound pressure levels in the receive room also change. The paper concludes with a general discussion and recommendations.
Sound insulation characteristics of shipboard windows
Authors: Kim Sangryul R. , Kim Hyun-Sil , Kang Hyun-Ju
Published: May 2008

Although small-size windows are used in a ship, shipboard windows are a multilayered structure with glasses and air-gaps for high sound insulation. This paper discusses how to improve the sound insulation performance of shipboard windows. First, the sound transmission loss (STL) obtained from various experiments with shipboard windows are introduced and studied. The results show the layer arrangement as well as the material property of each layer makes an effect on the window's STL. It is also found that the higher the sound insulation performance of the window is, the more important the effect of the window frame is. Next, theoretical investigations are carried out and discussed in comparison with the experimental results. The comparison provides possible clues to increase the STL of the window.
Predıctıng the acoustıcs of hıstorıc Istanbul Tunnel: Sımulatıon, calculatıon methods and geometrıcal detaıls
Authors: Bal Kocyigit Filiz
Published: May 2008

Istanbul Tunnel was designed and constructed by Eugene Henry Gavand in 1875 is the third Metro and second underground railway system in the world after Washington Metro (1868). In this paper, the acoustics of Istanbul Tunnel is investigated. This is a special case which sets up a challenge to these prediction methods. The shape of the tunnel and therefore focusing the sound, reverberant wall, and therefore fluctuation effect demands high accuracy in predicting the early reflections. The energy dissipates quickly in this type of enclosures and there is little masking effect of the reverberation. Another aspect that has been shown to give very different results in this case study is the geometrical detailing of the models. When Istanbul Tunnel compared with modern metrosystems; nowadays railway systems are controlled by modern electronic and mechanical system, but in the 19th century this electronic systems could not used. Solutions could be with the shape of the building. The aim of this paper is to clarify some of the problems that can arise in this type of constructions, and give guidelines for how they can be overcome/avoided. Another objective is to emphasize that room acoustic computer simulations, although very useful, need careful consideration about the underlying calculation methods.
Variation of mean free path length over time and its effect on room impulse response
Authors: Mijic Miomir , Sumarac Pavlovic Dragana
Published: May 2008

In their previous paper (Forum acusticum 2005, Proceedings, 2399-2404) the authors presented the local effect found in a large sports hall, described as significantly shorter reverberation time in the first 400-500 ms than that in the rest of the hall's long impulse response. To analyse this phenomenon, a new measure - mean free path length (MFPL) variation in time over the impulse response - was introduced. It is identified as the function of time obtained as an ensemble average in some fixed interval traced along the impulse response duration. The ray tracing simulation was used to calculate ray paths approaching the receiver in time. Analyzing MFPL variations over time is a new insight into the structure of room impulse response, and this paper presents its main characteristics, its dependence on geometrical properties of rooms, and also its relation to statistically defined mean free path length (4 V/S). The paper also presents a correlation between MFPL variation over time and the sound decay curve. The MFPL variation over time reveals the causes of the local effect introduced in the previous paper, but it is generally useful in explaining the sound decay monotony deviations.
Measurement-based fuzzy interpolation of room impulse responses
Authors: Huszty Csaba , Németh Bottyán , Baranyi Péter , Augusztinovicz Fülöp
Published: May 2008

Application of room impulse responses (RIRs) to acoustic evaluation and auralization often requires many measurements to get enough information about the hall, or to provide enough flexibility for virtual sound source placements in convolution reverberation. In this paper we propose a measurement-based fuzzy modeling method to approximate the RIR function at an arbitrary location between available measured points, without a priori information on the hall geometry or wall reflection parameters. For the fuzzy model identification we define an accuracy indicator of the spatial density of the source positions and predict the required number of them in a selected hall. This indicator quantifies the relationship of the early reflections, determined for various measured positions. This paper also proposes a method that treats nonuniform spatial sampling of the measurement positions, and its implementation for 2D cases is shown. Nonuniform spatial sampling can be useful when RIRs at some source positions -- e.g. positions of musicians on a stage of a concert hall -- are known or have to be measured precisely, but RIRs at locations in between require an approximation only. The proposed fuzzy model of RIRs actually transforms the measured information into a uniform and tensor product form, enabling the analyst to use further matrix and tensor algebra based numerical methods.
Comparison of automatic classification methods for beluga whales vocalizations
Authors: Leblanc Elisabeth , Bahoura Mohammed , Simard Yvan
Published: May 2008

The beluga whale is a loquacious marine mammal with a complex vocal repertory. It produces a wide variety of whistles and pulsed tones as well as high-frequency echolocation clicks. Automatic detection of the long-distance propagating communication calls are desirable for implementing passive acoustic monitoring (PAM) systems in their environment, for habitat utilisation studies and real-time early warning devices in anthropogenic impact mitigation systems. Signal processing methods were developed to classify beluga vocalizations from a PAM data set recorded in Cap-de-Bon-Désir in the Saguenay-St. Lawrence Marine Park in summer 2003 using a 6-hydrophones array with a 10-100 kHz sampling rate. The performance of an MFCC-based HMM system and a polynomial model applied to extracted time-frequency contours of vocalizations will be evaluated. The feasibility of real-time implementation will then be analysed for both methods.
Computer aided design of audio signal classifier systems
Authors: Huebner Sebastian V.
Published: May 2008

The problem of programming classifier systems for deterministic events in bioacoustic signals is seen as a knowledge engineering problem. Advantages and disadvantages of traditional approaches are discussed. A knowledge engineering approach for interactive visual classifier system design is described and advantages of the approach are highlighted. The basic architecture of a general purpose knowledge engineering framework for the acoustics domain is outlined. Emphasis is placed on both expert knowledge and on the role of data mining within the classifier system design process. Several examples illustrate how the approach can be used to create classifier systems for bioacoustic patterns in the time-frequency domain. Examples include multiscale spectrographic visualization, techniques to create and interactively modify subsymbolic and symbolic classifier systems for time-frequency patterns as well as the usage of three-dimensional visualizations to display hierarchical dependencies within complex classifier systems.
Correcting gray whale (Eschrichtius robustus) call rates in San Ignacio Lagoon, using sound exposure level measurements of ambient noise
Authors: Guerra Melania , Thode Aaron , Urban Jorge , Gonzalez Sergio
Published: May 2008

Autonomous acoustic recordings of gray whales (Eschrichtius robustus) were made in San Ignacio Lagoon, in February 2005-2008, while animals were present to breed and raise calves. Counts were made of the gray whales' most common vocalization, type S1. A sequence of semi-automated procedures was implemented to assist with call detection. Hourly call rates were computed for all seasons and adjusted for expected changes in detection range, caused by variations in the ambient background noise level. In this environment, the underwater acoustic background combines biological, oceanographic and man-made sources and can present changes of 10 dB above the average base level of 96dB re 1uPa 2-s between 350 and 750 Hz over semidiurnal scales. The relative changes in call rates in 2006 and 2008 are compared with visual survey counts conducted over the same period. The definition of SNR in the present study develops from energy flux densities or sound exposure levels (SEL). SEL were calculated experimentally through even sampling in time and individual sampling for each call. By assuming that the background masks a proportion of the detected calls, corrections were applied to determine the vocal activity within a fixed detection range.
Biosonar performance of a false killer whale (Pseudorca crassidens) improved with practice
Authors: Gisiner Robert
Published: May 2008

Cylinder wall thickness discrimination tasks have been used to assess the limits of dolphin biosonar. An attempt to replicate the benchmark data from a bottlenose dolphin (Tursiops truncatus) resulted in a surprising order of magnitude better performance by a false killer whale. The improvement came over multiple testing episodes, which suggests that initial limits to discrimination were overcome by learning; either through better understanding of the reinforcement contingencies, attention to novel sources of information within the returning echoes, or both. These results offer important insights into methodological considerations for testing animal psychophysical performance, especially for sensory performances like echolocation in which the subject exercises active control over the sensory input. The ability to improve sensory performance with practice also offers insights into the way the echo information is processed into an internal representation of external physical reality by the central nervous system, a process that is very likely open to improvement through experience, or learning, throughout the individual's life.
An analysis of Humpback whale songs for individual classification
Authors: Mazhar Suleman , Ura Tamaki , Bahl Rajendar
Published: May 2008

Acoustics based tracking systems are in use for studying cetacean behaviour. Such noninvasive techniques can also prove efficient for population assessment of vocally active species. One problem in this regard is to distinguish already counted reappearing cetaceans, even if reappearance occurs after a brief interval. In this connection we propose development of individual identification system for humpback whales (Megaptera novaeangliae) based on unique acoustic features underlying a song. Earlier we analyzed recognition performance of cepstrum based voice signature in seven humpback whales. The results were based on training and test data sampled from the same song. In this work, we test our hypothesis using data from different songs (i.e., recording timings of training and test data sets do not overlap) for two different individuals. Recognition rates for two individuals are above 80% and 95%, respectively. However an eight years old song gives degraded recognition rate of around 58%. The results give an insight into the effects of temporal song evolution on accuracy of our system. Our observations are followed by harmonic analysis of song units in two individuals. Cepstral coefficients and support vector machine (SVM) were used for classification and signal band-crossing rate was used for segmenting song units.
Phonemic segment characterization of Norwegian killer whale call types
Authors: Shapiro Ari D. , Seneff Stephanie , Tyack Peter
Published: May 2008

An important issue in animal vocal communication concerns the fundamental unit used to build signals into a repertoire and the syntactic rules associated with that assembly. Killer whale vocal production has traditionally been categorized by human observers into a set of discrete call types. These call types often contain internal spectral shifts, silent gaps and synchronously produced low and high frequency components. Such features motivated the analysis here which tested whether call types could be represented by a set of flexibly arranged and smaller phonemic segments. We evaluated whether segmented characterizations of stereotyped Norwegian killer whale calls yielded automated classification results of contour traces that paralleled a classification scheme using whole call type designations. Representations of calls in their entirety or as sets of either distinct or shared syllables did achieve similar performance. Calls composed of shared segments may provide a more parsimonious approach to parsing the vocal stream since there were fewer segments than call types, nearly 75% of all call types contained at least one shared syllable, and some syntactic patterns were evident. Such a system could flexibly generate new call types and contain the killer whale vocal repertoire within a subset of the possible combinations of segments.
Depth, orientation, and acoustics of sperm whales (Physeter macrocephalus) under natural and depredation foraging conditions in the Gulf of Alaska
Authors: Mathias Delphine , Thode Aaron , Straley Jan , Folkert Kendall , Calambokidis John , Schorr Greg , Burgess William C. , Lunsford Chris
Published: May 2008

In July 2007 bioacoustic tags were attached to adult sperm whales in the Gulf of Alaska under both natural foraging conditions, and situations wherein the animals were depredating sablefish from commercial longlining vessels. A small Rigid-Hull Inflatable was used to approach and attach a suction-cup acoustic recording tag on 13 occasions and stayed on animals for a total of 168 hours, yielding 80 h of depth, orientation, and acoustic data. These results, combined with passive acoustic tracking and underwater video-camera data, indicate that sperm whales depredate at depths shallower than 50 m, compared to natural foraging depths of 300-400 m in the area. During depredation the animals demonstrate changes in pitch and roll that are greater when compared with normal foraging behavior. Observations on the acoustic behavior of the animals are noted as well. The fact that these normally deep-diving animals depredate so close to the surface has interesting implications for both depredation-reduction strategies and biosonar research. [Work conducted under the SEASWAP program, supported by the North Pacific Research Board and the National Geographic Society.]
Accurate estimation of the duration of tonal signals emitted by marine mammals
Authors: Sentenac Nicolas
Published: May 2008

Passive acoustic marine mammals detection and classification is of great importance nowadays. The goal of this article is to present a tool that can be used to accurately measure the duration of tonal emissions from marine mammals, helping to classify them. Marine mammals emissions can be split into two different kinds and one of them is tonal emission. It can be defined by its narrow band frequency pattern. Narrow band signals can be detected in the time/frequency space thanks to the use of the spectrogram and thanks to a quadratic contrast criterion. The expression of this criterion for signal-only and noise-only is straightforward. This article will introduce the expression of a lower bound of the expectation of the criterion when signal and noise are mixed. As this lower bound is a function of signal to noise ratio, it can be used to threshold the criterion with the desired signal to noise ratio value. When the criterion is computed along time on a sliding window, narrow band signals with a higher snr than the thresholding one are detected as soon as they appear and until they vanish, giving an accurate estimation of the duration of such signals.
Slow chaotic changes in the excitability of the auditory units
Authors: Bibikov Nikolay G. , Dymov Alexandre B.
Published: May 2008

We explored the statistical properties of the spontaneous and evoked firing activity in the brainstem auditory units of the grass frog (Rana t temporaria). We estimated the properties of spontaneous firing using the following functions: interspike interval distribution, hazard function, autocorrelation functions for original and shifted sequence of interspike intervals, function of interdependence of neighboring intervals. The dependences of Fano and Allans factors upon the values of counting time (window size) were also obtained. We observed a considerable deviation of the spontaneous activity from the renewal process for the majority of units located both in the dorsal medullar nucleus (homolog of cochlear nucleus in the mammals) and in torus semicircularis (homolog of inferior colliculus). The negative correlation between the neighboring short interspike intervals was typical for some (mainly toral) units. However, generally week but quite reliable positive correlation between neighboring intervals was typical for the great majority of neurons. The values of Fano and Allan factors were close to 1 at window size less than 100-500 ms and increased in proportion to some power for larger window sizes. The exponents of these power dependences were different for different units.
Microacoustics: maintaining an ecologically relevant scale in insect bioacoustics
Authors: Morley Erica L. , Jonsson Thorin , Robert Daniel
Published: May 2008

A major challenge when studying an organism is to maintain its environment and context as reliably as possible. When looking at sensory systems it is crucial not to assume the animal's perception the same as ours and instead measure and mimic more accurately the natural stimuli driving the sensors. In insect bioacoustics the usual practice in playback and recording techniques overlooks differences in scale and context in which the organism's sensory system evolved. Here we present an approach to emit and record low-amplitude near-field sound, while maintaining an ecologically relevant scale, in Drosophila melanogaster. To mimic the effect of male courtship song on the female sound receiver (antennae) a mechanical microwing was constructed simulating, in power and geometry, particle velocity signals emitted by singing males, with its efficacy tested by behavioural assay. Development of a miniature particle velocity microphone was also initiated for recording signals in the fly's immediate vicinity (<2 mm) to elucidate the magnitude, temporal and radiation characteristics of the produced sound-field.
The effect of courtship song components in Drosophila melanogaster
Authors: Chen Yu-Po , Jackson Joseph C. , Windmill James F. , Robert Daniel
Published: May 2008

Courtship between male and female Drosophila melanogaster involves a complex emission of sounds produced by the male. This song comprises two aspects: a low-frequency sine song followed by a series of intense pulses. These songs increase the chances of the female accepting the male. However, the reason for the complexity of the song, and the effect on the female of the song's components, is poorly understood. Using measurements of the male courtship song for a canonical stimulus, we investigate the importance of the sine song on both the mechanical and electrophysiological responses of the female antenna: the nonlinear auditory sensor. While stimulating the antenna with modified courtship songs, antennal motion was measured using laser Doppler vibrometry, and compound potentials were simultaneously measured from the auditory neurones. Results show that, even at the periphery, there exists a significant change in the way the antenna responds to the pulses as a function of the sine song intensity, most emphatically through the neurophysiological signals. Results indicate that the sine song is an advantageous trait used to increase the female perception of the pulses in both time and amplitude sensitivity, and therefore improve the male's chance of successfully courting a female.
The Locust's tympanal mechanics
Authors: Windmill James F. , Bockenhauer Samuel D. , McDonagh Thomas R. , Robert Daniel
Published: May 2008

In the ear of the desert locust frequency analysis arises from the mechanical properties of the tympanal membrane. Incident sound is spatially decomposed into discrete frequency components through a tympanal travelling wave that funnels mechanical energy to specific tympanal locations, where distinct groups of mechanoreceptor neurones project. Initial analysis of the travelling waves employs conventional, steady state FFT, allowing a detailed analysis of the spatial composition of different frequencies onto the membrane. To further understand the exact mechanics of the tympanal travelling wave, its motion was also measured in the time domain to characterise its response to single impulse and single frequency stimuli, with a resolution of 390 ns. This allows the measurement of instantaneous wave velocity and the direct observation of wave compression across the tympanum. The locust tympanal membrane locust exploits tonotopic frequency analysis, in a similar sense to that of the travelling waves of von Békésy on the mammalian basilar membrane. However, von Békésy's wave is born from interactions between the anisotropic basilar membrane and surrounding incompressible fluids, whereas the locust's wave rides on an anisotropic membrane suspended in air. The locust's tympanum thus combines the functions of both sound reception and frequency analysis.