bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction of MRI-based three-dimensional atlas of the human tongue for tongue modeling
Authors: Wu Chao-Min , Wang Sung-Yi
Published: May 2008

The main purpose of this study is to build a MRI-based 3D tongue atlas for research on tongue morphometrics and physiological modeling of normal and disordered speech production. In this study, MRI data of 8 subjects (4 males and 4 females) were chosen from an orally-based MRI database of 20 male and 20 female college students without speech disorders. Sixteen landmarks were defined and selected from the 3D reconstructed MRI tongue images based on the subjects. Thin-plate spline analysis (TPS) was used to build a 3D tongue atlas for male and female subjects, respectively. Sagittal sections of the original MRI data were used to evaluate the accuracy of image registration and reconstruction. The resulted 3D tongue atlas was used to study subject-to subject, subject-to-atlas, and male-to-female morphometric variation. Preliminary results show the major difference among female subjects before and after the TPS analysis is in the area of tongue dorsum that is close to the velum and epiglottis, respectively. However, the major difference among male subjects is in the areas of tongue tip and body regardless of TPS analysis. In summary, our preliminary results imply that the 3D tongue atlas of female subjects show less subject-to-subject difference.
Neural correlates on Chinese speech production: an fMRI study
Authors: Wu Chao-Min , Lin Yi-Syuan
Published: May 2008

The aim of this study is to use functional magnetic resonance imaging (fMRI) method to find neural correlates on Chinese speech production. Three young normal adults (mean age 24 yrs) produced four tone Chinese characters "ma1, ma2, ma3, and ma4" in four ways: (A) normal speech, (B) mouthing speech, (C) unarticulated speech, (D) internal speech, and "ma1, ma1, ma1, and ma1" for the condition (E) normal speech. The fMRI results showed that the areas associated with the control of breathing for speech, vocalization, and hearing were the sensorimotor cortex, supplementary motor area, the superior temporal gyrus, the cerebellum, parietal association area, and the lingual gyrus. The areas associated with articulation were the sensorimotor cortex, the cerebellum, the inferior frontal gyrus, anterior and posterior cingulate gyrus, and the precuneus. The areas associated with tone variation were found in bilateral basal ganglia, hippocampal formation, and parietal association area, and the left pre-motor area, middle occipital gyrus, and the right cerebellum, superior temporal gyrus, and midbrain. Neural correlates of speech production and Chinese tone were all related to the cerebellum. In summary, our preliminary results showed the cerebellum plays an important role on Chinese speech production.
Differences in the development of speech segmentation abilities in two French dialects
Authors: Nazzi Thierry , Mersad Karima , Iakimova Galina , Sundara Megha , Polka Linda
Published: May 2008

Speech segmentation skills develop in infancy and are influenced by many phonological properties of the native language and, in particular, the prosodic structure of the infant's native language. Studies using the HPP task show that American English infants appear to favor a stress-based procedure (Jusczyk et al., 1999) whereas Parisian French infants favor a syllable-based procedure (Nazzi et al., 2006), in line with a prosodic-based bootstrapping account of segmentation abilities (Nazzi et al., 1998). However, in a study using different stimuli, Polka and Sundara (2003) found results that might suggest a developmental trajectory for Canadian French infants that does not rely on syllable-based segmentation. Given that the stimuli used in both studies on French were different, both research teams tested their infant populations (at 8, 12, and 16 months of age) with the stimuli originally used by the other team The results suggest a complex interaction between specific stimuli and infants' native dialect, thus providing for the first time data suggesting that word segmentation is dialect specific. We will discuss how these findings, together with acoustic analyses, show that early word segmentation is influenced by linguistic (rhythmic/syllabic, dialectal) prosodic cues, extra-linguistic (speech style) prosodic cues, and distributional cues.
Effect of consonant gemination on vowel coarticulation
Authors: Di Benedetto Maria-Gabriella , Domenicali Daniele
Published: May 2008

As well known V1CV2 structures are typically characterized by two different phenomena: the first vowel V1 spectral properties are affected by the presence and nature of the second vowel V2 (anticipatory effect), and V2 is influenced by the presence of the first one (cross-over effect). The intensity of anticipatory and the cross-over effects are language dependent and can vary significantly. Both effects have been observed in the past to be present in the Italian language through the analysis of VCV nonsense words. The Italian language has however a unique property, that is distinctive consonant gemination, i.e. consonant length is phonemic; two different words may thus differ by the sole presence or absence of gemination in one of this consonants. The Italian language offers therefore the ideal framework for analyzing the effect of gemination on across-consonant coarticulation. The object of this work is to analyze whether and how the presence of gemination may affect the acoustic properties of vowels in V1CCV2 words. First results of acoustic analysis of V1CV2 as well as their V1CCV2 counterparts, spoken by Italian native speakers, tend to show that gemination may have an effect on across-consonant coarticulation, with specific peculiarities for anticipatory vs. cross-over effects.
Speaker-specific patterns of token-to-token variability
Authors: Mooshammer Christine , Perrier Pascal , Fuchs Susanne
Published: May 2008

One explanation for token-to-token variability is neural noise corrupting the motor commands. In a previous study using a two-dimensional tongue model, adding neural noise to motor commands was able to account for shapes and orientations of the dispersion ellipses of tongue positions for non-high vowels only. It was concluded that additional sources shaping lingual variability patterns of vowels should be examined: (a) stabilization of the tongue by lateral palate contact, (b) palate shape and (c) perceptual constraints due to the crowdedness of the vowel space. Variability patterns of three speakers of German were analyzed by means of EMMA, EPG, and formant frequencies. Only the most variable speaker used lingual-palatal contact to reduce lingual variability for high front vowels. The other two speakers achieved articulatory vowel targets in a very precise manner. A flat palate shape can explain the limited lingual variability of one of these two. Only for this speaker did the acoustic distance between vowel targets significantly limit acoustical variability with smaller Bark ellipsoid volumes in regions with closer neighbors. For the other precise speaker, neither palate shape nor perceptual demands were relevant. We conclude that the relative importance of the factors analyzed varies across speakers.
Evaluation of the Pitch Estimation Algorithms in the monopitch and multipitch cases
Authors: Signol Francois , Barras Claude , Lienard Jean-Sylvain
Published: May 2008

Reliably tracking the fundamental frequency F0 of the components is an important step in the separation of superimposed speech signals. Several Pitch Estimation Algorithms are potentially usable and a rigorous evaluation method is needed in order to compare them. However, even in the monopitch case, many variations between them render such a comparison difficult. The extent of the F0min-F0max interval, the use of a priori information on the whole sequence or database, and above all the arbitrary setting of the voicing threshold, yield large differences in the results. These biases can be removed by setting the F0 bounds to fixed values acceptable for many voices, by proceeding with the evaluation on a strictly frame-to-frame basis, and by fixing the voicing threshold in order to get an equal error rate for overvoiced and undervoiced frames. In the multipitch case any frame may exhibit 0, 1, or 2 valid voicings according to the coincidence between the voiced and unvoiced parts of both signals. This problem is treated by defining a similarity measure linking the PEA's hypotheses to the pitch values of the isolated signals. The proposed methodology is applied to several PEAs, using the Keele database in monopitch and multipich setups.
An acoustic investigation of the Swedish child's acquisition of obstruent place of articulation
Authors: Van Doorn Jan , Karlsson Fredrik , Sullivan Kirk P.
Published: May 2008

Speech produced by children in the initial stages of development does generally not uphold as many phonetic distinctions as speech sounds produced by adults. A child's productions of different target words may therefore have similar acoustic properties and result in homonyms being perceived by the adult observer. This study presents a longitudional investigation into the development of place of articulation from non-distinctive to distinctive productions in word-initial obstruents produced by 22 Swedish children (aged 18 - 48 months). The data was collected through monthly recordings, approximatelly one year per child. The acoustic correlates analysed were spectral diffuseness, spectral skewness and spectral tilt for plosives and spectral skewness, spectral kurtosis, spectral variance and F2 onset frequency for fricatives. The results show a developmental trend in spectral skewness that is indicative of a increasing number of acquired phonetic contrasts. Spectral tilt change, F2 onset frequency, spectral mean and spectral variance provide evicence of within-category refinement wich is argued to be caused primarilly by advancements in motor control.
Nonlinear dynamics of speech categorization: critical slowing down and critical fluctuations
Authors: Lancia Leonardo , Nguyen Noel , Tuller Betty
Published: May 2008

The dynamical system view of speech perception assumes that speech categorization depends on both the acoustic properties of the incoming sound and the state of the perceptual system (indexed by the subject's responses to preceding sounds). Tuller and colleagues [1] systematically manipulated the order of presentation of stimuli from a "say"-"stay" continuum in a binary-choice word identification task. Listeners' responses were modeled using a nonlinear dynamical system whose point attractors were associated with perceptual categories. In the present study, we asked French speakers to categorize stimuli on a continuum from "cèpe" /sεp/ to "steppe" /stεp/. Our results provide support for two yet untested predictions from the model: the occurrence of a) critical slowing down and b) critical fluctuations. Critical slowing down relates to the increase in relaxation time that occurs as the system approaches points of instability. Critical fluctuations refer to the system's increased sensitivity to random fluctuations near the points of instability. [Work supported by the CNRS & French Ministry of Research, and by NSF.] [1] P. Case, B. Tuller, D. Mingzhou, and J.A.S. Kelso. Evaluation of a dynamical model of speech categorization. Perception and Psychophysics, 57:977-988 (1995).
The effects of vowel identification training on sentence-level speech recognition
Authors: Richie Carolyn
Published: May 2008

Recent work examined the effects of a novel computer-based approach to speech recognition training involving vowel identification [C. Richie, J. Acoust. Soc. Am. 121, 3045 (2007)]. When vowel identification training was done under auditory-visual conditions with noise participants demonstrated modest improvements in sentence recognition, and when training was done under visual-only conditions participants failed to show improvements in sentence recognition. However, sentence recognition was assessed for the CID Everyday Sentences in terms of words correctly recognized. Improvements in speech recognition may have occurred following training on a level lower than the word, and gone unrecognized given this scoring method. The purpose of the present study is to determine whether vowel identification training leads to improvements in speech recognition on a test of sentence recognition, as measured by correct identification of consonants and vowels. These findings have implications for sentence recognition test scoring methods. The role of acoustics in improving speech recognition will also be discussed. (Supported by Butler University HAC grant #027096).
An acoustic study on voiceless retroflex and dental sibilants of young native Min speakers in Taiwan
Authors: Chuang Yu-Ying , Fon Janice
Published: May 2008

The Mandarin spoken in Taiwan is influenced by Min, a Southern Chinese dialect, in many perspectives. Due to the absence of retroflex sibilants in Min, previous studies claimed that retroflex sibilants are replaced by their dental counterparts. Recent studies, however, showed that retroflex and dental sibilants are actually distinguished. Such contradictory result was due to the fact that different speaker groups were targeted at - one on older generation, acquiring Min as L1, whereas the other on younger generation, acquiring Min as L2. Since age and the acquisition order of Min were involved, it was unknown which factor affected the realization of retroflex and dental sibilants more. To clarify this point, we targeted at the younger generation that acquired Min as L1. Acoustic measurements were taken on all sibilants. Results showed that retroflex and dental sibilants had distinctive realization, suggesting age factor to be more determent. Gender effect was found significant, in which females showed a greater distinction than males. Moreover, retroflex sibilants pronounced in syllables were significantly different from those in sentences. Future studies could be done on the other group - older generation, acquiring Min as L2. Also, whether the frequency of using Min plays a role awaits further exploration.
A comparison of native speaker and American adult learner Vietnamese lexical tones
Authors: Blodgett Allison , Bauman Jessica , Bowles Anita , Charters Lykara , Rytting Anton , Shamoo Jessica , Winn Matthew
Published: May 2008

This study introduces a modification of the traditional carrier sentence elicitation task, provides new native speaker data regarding aspects of pitch and voice quality in Vietnamese lexical tones, and provides an empirical description of non-native speaker errors in tone production. Participants produce a series of three-word utterances in response to target words that appear individually on a computer screen in one of four colors. In this way, participants actively describe a changing event, while critical components remain constant: the identity of the word preceding the target, the target position (utterance medial), and the target's focus structure. Native speaker results are consistent with existing descriptions of fundamental frequency contours and creakiness. In addition, they provide evidence supporting claims that breathiness can occur in two different tones: the falling tone (huyen) and curve tone (hoi). Non-native speaker results suggest that adult learners struggle with voice quality distinctions and pitch shape.
Clicks with noisy accompaniment in West !Xoon
Authors: Grawunder Sven , Naumann Christfried
Published: May 2008

The current study is concerned with ingressive stops (clicks) with a noisy accompaniment exemplified by data from West !Xoon, a Taa variety ("!Xóõ", Tuu/Southern Khoisan) spoken in Namibia. Within the obstruent system of West !Xoon, we describe (1) aspirated clicks, (2) clicks followed by a laryngeal fricative, (3) clicks with an aspirated uvular accompaniment, and (4) clicks followed by a uvular fricative. In previous analysis for the variety of East !Xoon (Traill and Ladefoged, 1994), (2) were analysed as series of "delayed aspiration", while the contrast between (1) and (3) was ignored. A novelty discovery are prenasalized "voiced" clicks followed by [h], the voiced counterparts of clicks with "delayed aspiration", which are probably absent in East !Xoon. We present an acoustic analysis of alveolar and palatal clicks based on field data of 6 speakers (3 male /3 female), where for each click type plus noise accompaniment three tokens in #CV context had been recorded repeatedly. As descriptive parameters served durational measures of burst length, cluster length, length of aspiration delay, and spectral measures of burst and friction parts. In opposite to the previous distinction our findings suggest a clear 3-way distinction of clicks (1-3) with noisy accompaniment.
Blind source separation and directional audio synthesis for binaural auralization of multiple sound sources using microphone array recordings
Authors: Gunel Banu , Hacihabiboglu Huseyin , Kondoz Ahmet
Published: May 2008

Microphone array signal processing techniques are extensively used for sound source localisation, acoustical characterisation and sound source separation, which are related to audio analysis. However, the use of microphone arrays for auralisation, which is generally related to synthesis, has been limited so far. This paper proposes a method for binaural auralisation of multiple sound sources based on blind source separation (BSS) and binaural audio synthesis. A BSS algorithm is introduced that exploits the intensity vector directions in order to generate directional signals. The directional signals are then used in the synthesis of binaural recordings using head related transfer functions. The synthesised recordings subsume the indirect information about the auditory environment conveying the source positions and the acoustics similar to dummy head recordings. Test recordings were made with a compact microphone array and a dummy head in different indoor environments. Subjective listening tests were performed to compare the synthesized recordings with the actual ones for their performance in providing presence, spaciousness and envelopment.
Bilinguals' and monolinguals' reaction-time in two language contexts: evidence for the double phonetic representation in bilinguals
Authors: Garcia-Sierra Adrian , Champlin Craig
Published: May 2008

The time between the presentation of a stimulus and the response given to it is occupied by a series of mental operations reflecting the decision per-se. Reaction-time (RT) can be thought as the duration of the mental operations behind making a decision. Small RT values involve less mental operations than larger RT values. In speech categorization tasks, sounds with clear phonetic membership produce small RT values, and ambiguous speech sounds produce large RT values. In the present investigation a Go-No-Go task was implemented to assess RT from Spanish-English bilinguals (N=27) and English monolinguals (N=27) in two language contexts. Participants were asked to identify the speech sound "ta" from a 10 token speech continuum varying from -20 to +25 ms of VOT. It was expected that bilinguals, but not monolinguals, would perceive +VOT stimuli as clear representations of 't' (faster RT) in the Spanish language context, but as ambiguous representations of 't' in the English language context. The results confirmed the expectations. That is, language contexts affected the speed by which mental operations were produced in bilinguals. This outcome is in agreement with the idea that bilinguals possess a double phonemic representation. Challenges and limitations of the present study are discussed.
A detailed biomechanical finite element tongue model
Authors: Wilhelms-Tricarico Reiner F. , Stone Maureen , Carlson Mark , Buscemi Paul
Published: May 2008

For research on surgical modifications of the tongue, e.g., implants for treatment of sleep apnea, we built a detailed finite element model of the human tongue, to experimentally estimate and investigate muscle activations corresponding to observed movement data, and to study possible effects of tissue modifications. Most of the extrinsic and all intrinsic muscles of the tongue are represented as parametrized volumes within the tongue, and muscle fiber directions are specified by a tangent in curvilinear coordinate systems of parametric solids that overlay each muscle region. Fiber regions of different muscles may overlap, for example, for the transverse and vertical intrinsic muscles. Mixed Ogden type hyper-elastic models of strain energy density are used to represent passive tissue properties, and active contraction in muscle fibers is emulated by changing externally specified activation parameters in an anisotropic component of the strain energy density. The activation can vary over time and in its spatial distribution over a muscle, which is accomplished by specifying center point and spread of a Gaussian distribution in the muscle region. The tongue model is realized as a finite element implementation with large displacement/large strain calculations using incompressible 8-node elements in a commercial FE code (Marc by MSC-Software).
Real-time acoustic blind signal separation system based on the spatio-temporal gradient analysis
Authors: Teramoto Kenbu , Khan Md. Tawhidul Islam
Published: May 2008

This paper presents an autonomous directivity microphone system for the blind source separation based on the newly proposed spatio-temporal gradient algorithm. The blind source separation technique principally uses no a priori knowledge about parameters of convolution, filtering, nor mixing. In the simplest case of the blind source separation problems, the observed mixing signals are the linear combinations of unknown source signals which are mutually and statistically independent and contain zero mean. The proposed blind signal separation algorithm utilizes the linearity among the four signals: (1) the sound pressure, (2) x, (3) y, and (4) z-directional particle velocities, all of which are governed by the wave equation and the equation of motion. The proposed method, therefore, has an ability to simplify the convoluted blind source separation problems into the instantaneous blind source separation problems over the spatio-temporal gradient space. Several acoustical experiments have been performed with acceptable performance of the proposed method of blind source separation. A sensor for measuring the particle velocity of acoustic signal has been used in the experiment.
Signal analysis in acoustic microscopy for nondestructive inspection of varnish layers on metal substrates
Authors: Brand Sebastian , Czuratis Peter , Raum Kay
Published: May 2008

For preventing corrosion and for surface protection metallic objects are commonly finished with layers of varnish. The integrity of the varnish and potential defect propagation influence the durability of the metal and hence are a measure for the quality of the finishing. Scanning acoustic microscopy provides high axial and lateral resolution, a sufficient penetration depth and is nondestructive. The goal of this work was the development of a method for detection and evaluation of delaminations of varnish layers on metallic surfaces. Investigated were samples containing one and two layers of varnish. One group contained priming only whereas the second group contained varnish on top of the undercoat. The surface integrity of the finishing was destroyed by a scratch through all finishing layers. Defect aging was then performed by exposing the samples to a corrosion-friendly atmosphere. Scanning acoustic microscopy combined with signal analysis was performed for investigating the connectivity between the finishing layers and the substrate. A robust numerical deconvolution technique has been adapted and optimized to enable the separation of strongly overlapping pulses. Echoes originated at the substrate and the finishing layers have been localized and layer thicknesses/distances were estimated. Delaminated spots of the finishing were successfully evaluated using the method developed during this study.
Flaw detection and thin materials thickness measurement using time frequency and high resolution algorithms
Authors: Drai Redouane , Khelil Mohamed , Megherbi Fouzia , Benammar Abdelsaalam
Published: May 2008

Several techniques of signal processing were introduced in ultrasonics NDT field. In thin samples the reflected signals are overlapping thus making detection of defects in these samples and accurate measurements impossible. It is thus necessary to enhance the visibility of the defect echo by signal processing techniques. In this context, we develop signal processing tools allowing detecting and locating the imperfections present in these materials. In this paper, we contribute by the development of some signal processing techniques based on time frequency and high resolution algorithms in order to enhance the resolution of flaw detection and to measure thin materials thickness. 1- We propose to implement temporal versions of methods known as high resolution like MUSIC, Root MUSIC and Eigen vectors method. These methods allow frequencies extraction in the case of the complex signals drowned in noise. 2- We apply time-frequency algorithms based on STFT, Wigner-Ville, Gabor transform on thin materials thickness measurement. A comparative study is carried out between all of these algorithms and is applied in separation of closer flaw echoes and thin materials thickness measurement. Satisfactory results are obtained with Gabor transform in measurement of few tenth (0.1) mm.
Ultrasonic structural health monitoring by multiple-input-single-output minimum variance processing
Authors: Krolik Jeffrey , Hickman Granger , Carin Lawrence , Michaels Jennifer E.
Published: May 2008

This work concerns ultrasonic detection and localization of defects in platelike metal structures such as airfoils. In previous work, MIMO delay-and-sum beamforming has been used to image these defects using change-detected ultrasonic signals between a sparse array of transmitters and receivers. However, mismatch of medium dispersion and unknown scattering properties of the defects can lead to significant imaging artifacts. To reduce imaging artifacts and sidelobes, a multiple-input-single-output (MISO) minimum variance (MV) approach is proposed here. MV-MISO imaging involves electronically scanning a transmit beam over the area of interest while, at each point being imaged, virutal transmit nulls are adaptively steered in the directions of interfering scatterers. For each imaging cell, this is achieved by adjusting transmit weights to minimize the variance of signals received at a single receiver subject to the constraint of achieving constant insonification. Using a model of dispersive Lamb wave propagation, the proposed algorithm has been successfully applied to change-detected data gathered with a six-sensor transmit-receive array coupled to a thin aluminum plate with artificial defects (e.g., drilled holes).
An accurate distance measurement by calibration of doppler-shift for ultrasonic sonar sensing
Authors: Shinnosuke Hirata , Kurosawa Minoru K. , Katagiri Takasi
Published: May 2008

Ultrasonic distance measurement with the pulse-echo method is based upon the determination of the time of flight of ultrasonic waves. The pulse-compression technique, which involves the calculation of the cross-correlation function between the transmitted and the reflected waves, is the conventional method for improving the resolution of the measurement. The calculation of a cross-correlation operation requires high-cost digital signal processing, however. This paper presents a new sensor signal processing method of the pulse-compression technique using a delta-sigma modulated single-bit digital signal. The proposed method consists of three parts: an analyzing operation of the doppler-shifted frequency, a cross-correlation operation by single-bit signal processing, and a smoothing operation accomplished by a moving average filter. For the pulse-compression technique, this method reduces the calculation cost of digital signal processing. Since the frequency of the linear chirp signal is doppler-shifted, the distance from the moving transmitter to the moving object cannot be accurately measured in the pulse-compression technique. To solve this problem, the analyzing operation of the doppler-shifted frequency is used to calibrate the transmitted ultrasonic wave, thus effectively improving the accuracy of the measurement.
Temporal approach of the synthetic aperture imaging using Hadamard matrix
Authors: Mosca Frédéric , Nicolas Jean-Marie , Kopp Laurent , Couade Mathieu
Published: May 2008

The synthetic aperture imaging is a very promising solution in the well-known compromise between contrast and frame rate. Indeed this method leads to the measurement of each transmitter/receiver impulse response of the system. From this fact, synthetic aperture imaging reach the transmit/receive focus imaging quality for the cost in frame rate of the number of antenna's elements. The main inconvenient of this method is the very low signal to noise ratio provided. Indeed, using only one transmitter per sequence leads to a very poor penetration. To correct this, a method using spatial Hadamard sequences has been introduced. For each of this Hadamard sequence, a Hadamard beam is generated in the medium. By a temporal approach, some interesting properties of those beams are highlighted and a method using those properties is proposed. Some experiments have been done using those properties and the results show an important improvement of the frame rate for a very small cost in contrast.
Elastic-wave reverse-time migration imaging with a new vector-imaging condition
Authors: Denli Huseyin , Huang Lianjie
Published: May 2008

With increasing computing capability, the use of elastic waves in three-dimensional subsurface imaging is becoming more feasible. However, the research in this area is still in the embryonic stage. In conventional seismic imaging, multicomponent data are decomposed into compressional and shear components, and solutions of the acoustic-wave equation are used to process each component independently. Such an imaging technique, however, cannot correctly handle elastic-wave conversions/couplings in complex regions, which is critically important for high-resolution and reliable imaging. In this paper, we develop elastic reverse-time migration imaging, applying a finite-difference solution to the pure elastic-wave equation in heterogeneous media. We implement numerical reverse-time migration imaging in a scheme similar to time-reversal acoustics in the laboratory. To correctly handle polarizations of compressional- and shear-waves during imaging, we also develop a novel vector-imaging condition for elastic-wave reverse-time migration. We use synthetic reflection data to demonstrate that, compared with the conventional imaging condition, our new vector-imaging condition increases image resolution and reduces image artifacts. The new imaging algorithm can significantly improve our capability to image complex subsurface structures.
A parametric study of interactions between acoustic signals reflected by the seafloor
Authors: Pinson Samuel , Guillon Laurent
Published: May 2008

This paper deals with the study of broadband acoustic signals reflected by the seafloor and recorded on a vertical array in shallow water areas. Only the first bottom reflected path is considered here. In previous studies (see e.g., Guillon and Holland, JASA, 122, 2974), two different aspects of the "coherence" of these signals were examined (the maximum of the cross-correlation coefficients and the phase of the cross-spectra) and it was shown that these parameters are sensitive to the geoacoustic nature of the seafloor. These results show that the interactions between signals can be used efficiently for improving geoacoustic inversion schemes or for transmission loss predictions. Before going to such applications, a detailed parametric study is needed to investigate the sensitivity of the interactions measurement to various parameters (range, geoacoustic structure,...). This is done using a numerical model, based on the spherical wave decomposition of plane waves, that simulates the signals reflected by the seafloor. The parametric study lead shows the relative importance of the various parameters and gives indications for the possibility of inverting these parameters.
Underwater stereo-photographic measurement of small scale roughness: limits to spatial correlation accuracy
Authors: Canepa Gaetano , Pouliquen Eric , Lyons Anthony P.
Published: May 2008

In recent years stereo-photogrammetry measurements of seafloor small scale roughness have been reported in the literature. Stereo-photogrammetry algorithm consists of a comparison between areas (windows) belonging to corresponding regions of a pair of photos. This comparison may be performed numerically or by human eyes using a photogrammetric stereocomparator. The results of this process are then converted in an array of seafloor heights. Until now underwater stereo-photographic data are given with no quantitative measurement of the positions and position correlation lengths errors: this work addresses this problem applying the results to the SAPHO system (Seafloor Automatic PHOtogrammetry) developed at NURC. It is shown that positional error estimates for stereo-photographic systems must take into account not only line/matrix resolution and system geometry but also the effects of comparison window size and image quality. A method by which this can be achieved is described. It is also shown that the stereo-photographic systematic error has an important effect when the purpose of the measurement is to determine seafloor correlation length or power spectral density for acoustic scattering estimation.
Bubbles at the top and bottom of the water column: the acoustical effects, and the use of acoustics to measure them
Authors: Leighton Timothy G. , Coles David , Ainslie Michael A. , White Paul R.
Published: May 2008

Bubbles of atmospheric gas can be entrained by breaking waves at the top of the water column: this bubble population is dynamic, and will evolve through the effects of buoyancy, gas exsolution and dissolution, and the fragmentation and coalescence of bubbles. These processes are important to ambient noise, sonar operation, and the overall gas budget of the planet. At the base of the water column, methane bubbles can occur in marine sediments, a phenomenon important to the global methane budget, to the petrochemical industry, and to the stability of the sediment (e.g., for civil engineering purposes). This paper examines the acoustical effects of both of these populations, and the ways in which acoustics can be used to measure them. Data will be presented from field trials, including measurements of gassy marine sediments in UK waters, and of wave-generated bubble clouds measured by an 11 m spar buoy deployed from 16th June to 18th July 2007 at a distance of 400 miles off the west coast of Portugal.
Sonic-boom noise under a wavy air-water interface
Authors: Fincham Adam M. , Maxworthy Tony , Cheng Hsien K. , Griffice Charles P. , Wang Johnson C. , Edwards John R. , Hashad Adel A.
Published: May 2008

Recent investigations of the underwater sound field produced by sonic booms show that the latter's interaction with surface waves can strongly alter the sound level, frequency range, and signal waveform reaching the deeper part of the ocean. Unlike conclusions from studies based on the flat-ocean model of Sawyers [1] which indicate little effects at depth beyond one signature length, the interaction of sonic-boom waves with a surface-wave train can generate nonevanescent, downward propagating waves which, owing to their lower spatial-attenuation rate, overwhelm the otherwise primary (flat-ocean) wave field. Theoretical results [2] substantiate and elucidate the significant differences between flat and wavy surfaces in waveform characteristics and their audibility in deep, and moderately deep water. Here we report on an extensive series of laboratory experiments performed specifically to validate this theoretical model and to ascertain the distinct differences in wave-field characteristics between a wavy and flat interface. The experimental measurements confirm the theoretical findings, showing the predicted differences between the sound fields measured under wavy and flat air-water interfaces stimulated by a passing sonic boom. [1] Sawyers, K. H. J. Acoust. Soc. Am., 44(2), 523 - 524, (1968) [2] Cheng, H. K. and Lee, C. J., J. Fluid Mech. 514, 281-312 (2004).
Acoustical design consideration for the new IFEZ concert hall
Authors: Jeon Jin Yong , Kim Yong Hee , Sato Shin-Ichi
Published: May 2008

The design of a new concert hall for the Incheon Free Economic Zone (IFEZ) Arts Center in Korea is in progress. The hall is supposed to be the home of the Asia Philharmonic Orchestra. It has over 1,700 seats, including 150 choirs. A vineyard seating arrangement will be applied, but the seats around the stage area will be minimized in order to form a solid stage enclosure. Lateral walls are designed for each seating block to increase acoustical intimacy. Average width between lateral walls has been designed to be less than 15 m, and every seat is arranged within 7.5 m to the closest lateral wall. All lateral walls are designed to be inclined to lead first reflections and to improve spatial impression at the audience area. Diffusers are functionally installed to the effective reflecting surfaces from the source on stage. The design considerations are investigated through both computer simulation and scale modelling.
New design tendencies in modern concert hall design
Authors: Bassuet Alban A.
Published: May 2008

New concert hall design trends are emerging as seen from recently completed halls around the world and recent international architectural competitions. Analyzing the current situation, the paper starts by differentiating the acoustical characters of major traditional concert hall forms such as the large shoe-box, the Vineyard and the surround hall. It discusses in particular the balance of acoustical energy that characterize these different basic hall shapes, the sensation of intimacy in relation to the listener's distance to the performance area and the different early reflection patterns inherent from these hall shapes. As an example of modern concert halls design tendencies, the paper then describes a design option chosen by Arup Acoustics for the Paris Concert Hall Architectural design competition with Zaha Hadid architect. The paper describes the development of the form and shape of the hall in response to the brief, the concept chosen for the design of sending/receiving surfaces to improve the early reflection "efficiency" and "stability" and the use of an overhead reflector to improve the balance between soloist and orchestra and the balance between the orchestra and the reverberation in the hall.
Acoustic design and evaluation of a multi-purpose hall of a new conference centre
Authors: Nagy Attila Balázs , Tamás Ferenc , Kotschy András
Published: May 2008

At Forum Acusticum 2005 the building and room acoustic design of a new Conference Centre was presented. Since then the construction work has been finished and the Centre is now open. The Conference Centre itself is a multi-functional building, having three wings of different functions. The Main Hall of the Centre is a room for 750 people which can be extended with adjacent section rooms for 1100 persons, giving a total volume of 14000 m3. It was designed to host conferences, lectures, and - most of the time - to be used as a concert hall. The extremely different acoustical demands of being a concert hall and a lecture room had been fulfilled with appropriate room acoustic design and with variable acoustics by employing a DCR (Digital Control of Reverberation) system. In this paper we give a report on the achieved acoustical performance of the Main Hall of the Conference Centre. We have performed extensive room acoustic measurements in the Main Hall, the results of which are compared to the designed values and are presented in this paper. The design of the DCR system is discussed in a different paper.
Evaluation of virtual acoustic stage support for musical performance
Authors: Woszczyk Wieslaw , Martens William L.
Published: May 2008

The effects of performance space acoustics on musical performance can be evaluated most effectively by eliminating the influence of powerful non-auditory factors, such as the visual appearance of the performance space. To allow for such relatively unbiased evaluations, a virtual acoustic stage support system was set up for a live musical performance, and the performer was asked to make blind comparisons between a variety of architectural acoustic simulations. While results support the broad generalization that the preferred reverberation time for acoustical stage support depends upon the piece of music to be performed, it was also clear that preferences strongly depended upon performers' aural familiarity with architectural acoustic spaces in which they had considerable experience in previous performances. After some exposure to descriptive analysis techniques, performers could explain their preferences in terms of the perceptual characteristics that differed between presented aural architectures.
Effects of Low-frequency Absorption on Perceived Tightness of Bass Imagery in Music Reproduction
Authors: Martens William L.
Published: May 2008

In order to enable unbiased observation of the effects of low-frequency absorption on auditory imagery associated with multichannel loudspeaker reproduction, binaural recordings were made of surround sound program material that was reproduced over full-range loudspeakers located in a room that was specially constructed to allow for variation in low-frequency acoustical treatment. These recordings were then presented via headphones to allow for double-blind comparison of the variation in auditory imagery associated with selected changes in room acoustics while holding listener and loudspeaker locations constant. Several perceptual attributes were examined, but the listeners were able to make the most clear distinctions between auditory spatial images in terms of the attribute identified as the "perceived tightness of bass imagery." Analysis of the signals presented to the listeners' ears in these binaurally-reproduced multichannel music samples showed that the tightest bass imagery was associated with high values of interaural coherence, with lower values producing more "muddy" bass imagery. [Work supported by Canada Foundation for Innovation.]
Acoustical tests of custom-made, low-cost bass absorptive treatment for small rooms
Authors: Pieleanu Ioana , Fullerton Jeffrey , Choiniere Marc
Published: May 2008

Small music classrooms, practice rooms or small budget recording studios and control rooms are a few of the numerous applications where low frequency absorption is sought and necessary for a well-balanced acoustical spectrum. Often, low frequency absorption is achieved by using pre-engineered products, such as tuned panel resonators. Unfortunately, the cost of these pre-engineered products can be excessive for small budget projects, or projects that involve a large number of such spaces. For these applications, more affordable, custom-made low frequency absorbers are desired. Several types of custom-made treatments were physically tested, to determine if the degree of low frequency absorption they provide would make them an effective replacement for the pre-engineered counterparts. The test samples included glass fiber panels mounted as corner traps, custom-made plywood panel resonators and others. The testing was conducted in a space comparable in size to a small studio room/control room, or a medium practice room. This presentation describes the test method and measurement results.
The importance of bass clarity in pop and rock venues
Authors: Adelman-Larsen Niels W. , Thompson Eric R.
Published: May 2008

High levels of bass sound have been shown to stimulate the part of the brain that controls such basic instincts as sexual desire and hunger [Todd, 2000]. In rock and pop music, the bass frequencies from 40-125 Hz get amplified to very loud levels. Easily half of the electrical power of the PA and monitor system goes to these 1.5 octaves. A recent survey [Adelman-Larsen et al., 2007] showed that the most important subjective parameter for a rock and pop music hall to score a high rating was 'bass clarity' which correlated with a coefficient of 0.74 to 'overall impression'. Informal discussions with audio engineers and bass players give the perspective that artificial reverberation is rarely, if ever, added to bass-frequencies. In fact the ideal hall should be as dry as possible at low-frequencies. In the mid-treble frequency range, sound absorption, and thereby 'clarity', is easily obtained through the presence of the audience that absorbs 4-6 times more mid/high frequency sound energy than bass sound energy. In the low-frequency range 'clarity' is not so easily obtained. This paper discusses the challenge in depth and proposes design solutions.
Investigation of Bonello criteria as a practical tool in small room acoustics
Authors: Welti Todd
Published: May 2008

The Bonello criteria are often used as an objective metric for assessing room dimensions with respect to modal response. In reality, the modal response is not simply a property of the room dimensions, but is quite dependent on source/receiver locations as well. The legitimacy of Bonello's criteria when used in rooms with typical subwoofer and seating configurations has not been well investigated. In this study, a room model is used to calculate room responses for a large number of combinations of room dimensions, subwoofer positions, and seating locations. The Bonello criteria are evaluated for each combination and compared to perceptually relevant criteria such as flatness and seat to seat consistency of the calculated acoustical responses.
Different approaches for efficient finite element modelling of absorbers in small rooms
Authors: Aretz Marc
Published: May 2008

The FEM is a powerful tool for the numerical simulation of sound fields in enclosures. It accounts for the modal characteristics of the sound field, which are dominant at frequencies below the Schroeder frequency and it is also possible to model the mutual coupling between airborne and structure borne sound fields, when an appropriate structure model is implemented. When applying the FEM to complex room acoustics applications, like e.g. a control room in a recording studio, it is a challenging task to specify realistic boundary conditions. Different kinds of acoustical absorbers like Helmholtz resonators, plate absorbers and complex layered porous absorbers are found in these environments. While it is possible in principle to use complex and exhaustive models for these acoustical absorbers, it is often computationally much more efficient to use acoustic impedances or two-port network FEM elements to represent the fluid structure interactions. In the course of this study we compare different approaches for the modelling of Helmholtz resonators (without and without flow resistance), since it has proven very costly in terms of computation time to explicitly model every single hole in the resonator boxes. The simulation results are compared with results measured in a model room.