bluuebunny/crossref_metadata_2025 huggingface dataset:
Age effects of pitch-shifted auditory feedback on reflexive and volitional voice F0 control
Authors: Nagao Kyoko , McCurdy Katie E. , Burnett Theresa A.
Published: May 2008

Research on voice fundamental frequency (F0) control suggests that when making a voluntary vocal response to a pitch change in voice auditory feedback, the pitch-shift reflex typically occurs before the volitional response is initiated. The current study examined the effects of aging on reflexive and volitional voice F0 responses to pitch-shifted auditory feedback. Thirty participants (age range 19 to 78 years) repeatedly sustained an /u/ vocalization at a steady pitch and loudness while listening to their voice fed backed over headphones. Once per vocalization, feedback pitch was randomly shifted upward or downward for 100 milliseconds and 20 or 100 cents. In the Sustain condition, participants attempted to ignore the pitch change in auditory feedback voice. In the Follow condition, participants immediately changed their pitch in the same direction as the auditory pitch shift they heard. Preliminary results from thirteen participants indicate that there appears to be no effect of aging on the first F0 responses for both magnitude and latency. Voluntary voice F0 changes were delayed in older participants compared to younger participants as expected due to age-related general slowing. Results broaden our understanding of typical reflexive and volitional voice control capabilities across the age span.
Neural mechanism for understanding speakers' intentions: developmental analyses of children with and without communication disorders
Authors: Imaizumi Satoshi
Published: May 2008

Ability to understand speakers' intentions through linguistic contents and affective prosody is examined for children between 5 and 12 years-old with and without communication disorders. Four types of spoken short phrases, expressing admiration, sarcasm, blame, and humor or joke, were presented. For each stimulus, the subjects were asked to choose between two cards, one with a written word "praise" and another with "no praise" accompanied by corresponding drawings. For children without any communication disorders, the percentage of the correct judgment of speaker intentions was high and stable for admiration and blame phrases which have congruent linguistic and affective valences. It was significantly low for 6-year-old children and increased with age for the sarcastic or joking phrases which have incongruent linguistic and affective valences. The percent correct was significantly lower for autistic children than normally developing children particularly for the phrases with incongruent valences. Although a significant difference was found between children with severe- and mild-hearing impairment, no significant difference was found in the percent correct between the congruent and incongruent phrases for them. Based on these results together with brain activation analyses using fMRI (Imaizumi et al., 2004, 2006), a model of neural mechanism for understanding speakers' intentions is discussed.
Lip protrusion and constriction in anticipation in English and French
Authors: Noiray Aude , Ménard Lucie , Cathiard Marie-Agnès , Abry Christian
Published: May 2008

Though lip constriction is acoustically the most robust parameter for rounding, most studies on anticipatory coarticulation relied on the investigation of protrusion via EMG, optoelectrical systems or audiovisual processing. These various methods produced inconsistent anticipatory profiles across studies or even speakers. The Movement Expansion Model (MEM) of Abry and Lallouache has explained vocalic anticipatory coarticulation in four French adults and eight children via lip constriction, showing idiosyncratic behaviours, i.e. personal regression slopes but with a lawful variability validated by high correlation coefficients. In order to describe global anticipatory movement, the current study included measures of both protrusion and constriction over time. Four American English and four Canadian French adults were audio visually recorded, uttering [iC[n]u] sequences, in which C[n] corresponded to a varying number of intervocalic consonants. Lip protrusion was measured via an Optotrak system, and constriction via a Lip-Shape Tracker (from ICP Grenoble). We found that when tested on lip area control, English speakers joined French speakers in a regular MEM temporal pattern, displaying their own anticipatory behaviour, with personal regression slope or expansion coefficient.
The contribution of vowel production to the intelligibility and accentedness of nonnative speech
Authors: Alexander Jessica E. , Sidaras Sabrina K. , Nygaard Lynne C.
Published: May 2008

The present study investigated the extent to which the perception of accentedness and intelligibility in nonnative speech depends on the specific acoustic realization of vowels produced by nonnative speakers. Twelve native speakers of Korean were recorded producing both word- and sentence-length English utterances. Acoustic analyses, including measures of vowel duration and formant frequencies, were conducted on tokens of individual English vowels identified from the word-length utterances. Vowel tokens were selected from a variety of phonetic contexts and were compared to productions of the same vowels produced in the same contexts by native English speakers. A separate set of native English-speaking listeners judged accentedness and intelligibility from the sentence-length utterances. The results showed that both the duration and spectral characteristics of Korean-accented vowels were related to overall sentence intelligibility and ratings of perceived accentedness. These findings suggest that the detailed acoustic realization of the temporal and spectral structure of non-native vowels contributes to global measures of perceived accentedness and overall intelligibility.
Pitfalls of spectrogram readings of flaps
Authors: Son Minjung
Published: May 2008

Several acoustic studies have revealed stable characteristics of the speech signal for rhotics, whereas articulatory studies have found different articulatory strategies across speakers for producing these segments (Ladefoged and Maddison, 1996; Tiede et al., 2004). However, no study has showed that the phonologically reduced flap gesture, which is argued to be a lateral in the underlying representation, can sometimes fail to be reflected in the acoustic correlates of an articulatory event. Using electromagnetic midsagittal articulometry (Perkell et al., 1992), a case study has been conducted for Korean. Productions of two Seoul-Korean speakers were collected using real words in the within-word condition. The subjects read target words within a single accentual phrase, as in Jun (1993), and repeated eight times. Each target word (/ili/ and /ala/) appeared in its own distinct natural sentence at two speech rates (fast and comfortable). A total of 32 tokens were available for analysis. Tongue tip gestures were examined simultaneously with spectrograms. Results from one speaker indicated that sometimes no acoustic correlates of the tongue tip gesture for a flap were present (6.3% of productions) although articulation was obviously produced [Work supported by NIH DC00403.]
Fine-grained sediment layers: an acoustic lens for sub-bottom sediment processes and structures
Authors: Holland Charles W.
Published: May 2008

In many coastal and deep water regions, there is a layer of fine-grained sediment (e.g., clay and silty-clay) over coarser grained sediments or rock. This layer may range from scales of centimeters to hundreds of meters thick. Fine-grained sediments typically have a sound speed less than that of the interstitial fluid (i.e., overlying water column) with modest attenuation and thus act as a refracting lens for the acoustic field as it interacts with sub-bottom structures. The presence of fine-grained sediments frequently opens an effective window for acoustically probing very small-scale processes within the sediment. The presence of fine-grained sediments also has a profound impact on seabed reflection and scattering, hence propagation, reverberation, and clutter. The effect of fine-grained sediment layers (along with concomitant sub-bottom processes) on reflection and scattering is discussed using both theory and measurements. [Research supported by ONR OA321.]
The effect of wind-generated bubbles on sea-surface backscattering at 940 Hz
Authors: Van Vossen Robbert , Ainslie Michael A.
Published: May 2008

Predictions of sea-surface backscattering strength are needed for sonar performance modelling. Such predictions are hampered by two problems. First, measurements on surface backscattering are not available at small grazing angles. These are of special interest to low-frequency active sonar since these mainly contribute to long range propagation. Second, existing theoretical models underestimate the surface backscattering strength at larger grazing angles. We investigate whether wind-generated bubbles can explain this deficit. Thus, we develop a theoretical description which includes the effect of refraction and scattering of sound by wind-generated bubbles. We compare the theoretical surface backscattering predictions to Critical Sea Test measurements. These are a set of backscattering measurements for different wind speeds, and grazing angles are in the range between 5 and 30 degrees. The comparison shows that a good fit can be obtained between the theoretical predictions and the surface backscattering measurements, depending on the population density of resonant bubbles. This indicates that wind-generated bubbles significantly contribute to rough-surface back-scattering. The bubble backscattering contribution is dominant at large wind speeds and also at small grazing angles.
Unperturbed normal mode method for forward surface scattering
Authors: Henyey Frank S. , Thorsos Eric
Published: May 2008

A technique is presented that uses an expansion in unperturbed modes to calculate acoustic scattering from ocean surface waves in a shallow water waveguide. The basic formalism as well as a useful extension to account for the difference between the water column and the domain in which the modes are calculated. The coupling between the modes due to the waves is local at the ocean surface, unlike the coupling of local modes. Numerical examples of the calculation are given for both a sinusoid surface wave and a random surface wave with a typical wind driven spectrum.
Improving room acoustics at low frequencies with multiple loudspeakers and time based room correction
Authors: Nielsen Sofus Birkedal , Celestinos Adrian
Published: May 2008

Small and medium size rectangular rooms are often used for sound reproduction. These rooms have substantial acoustical problems at low frequencies primarily caused by the reflections from the room boundaries. The spatial variation in sound pressure level (SPL) can be up to 30 dB in a room at low frequencies, and appear not only at modal frequencies. The problem is an acoustical issue in time, and should therefore be analyzed in the time-domain, instead of the traditional steady state frequency domain. The construction of a finite-difference time-domain approximation program (FDTD) has lead to a simple and untraditional solution called CABS (Controlled Acoustical Bass System) that makes use of multiple loudspeakers. With the proper placement of low frequency loudspeakers, CABS can create a plane wave from the front wall which will be absorbed by additional low frequency loudspeakers at the back wall. With the back wall reflection removed a homogeneous sound field will be created in the whole room at low frequencies. Simulations and measurements of normal size listening rooms show that 4 loudspeakers are enough to even the sound field in a room. The CABS system is controlled by a developed DSP system.
Active Sound Field Equalization
Authors: Omoto Akira , Suzuki Hisaharu , Kakiuchi Akihiro
Published: May 2008

Dominant acoustic modes often result in the inevitable non-uniform distribution of the acoustic quantities such as sound pressure, especially in the small sized enclosure. In our study, active control technique is thus introduced to overcome the adverse effects of such modes. Instead of the squared sound pressure which is normally adopted in active noise control, the quantity to be controlled is selected as the weighted values of acoustic intensities or the acoustic impedances in rectangular directions such as x, y and z measured at plural points. The reasonably selected combinations of weights yield the control outputs which can alter the directions of propagating waves and result in reducing the complicated standing waves. Further, results of numerical simulations suggest that the well balanced arrangement of the primary and the secondary sources can 'rectify' the propagating direction and result in the uniform distributions of sound pressure. The strategies used in this study have possibilities of realizing useful controller for active sound field equalization.
The effect of diffusers on low frequency modes
Authors: Angus Jamie A.
Published: May 2008

Small listening rooms are becoming prevalent, due to the availability of production facilities on personal computers, and the financial pressures faced by the industry. In these rooms, modal behaviour at low frequencies significantly affects the quality of the reverberant decay, due to their non-diffuse nature compared with other frequencies. Diffusion and absorption can help and may be a useful way of improving the low frequency performance of such rooms. This paper discusses the properties of these rooms at low frequencies, in particular the effect of diffusing boundaries on the modal behaviour of such rooms. The paper will first discuss what is meant by a mode and modal decay. It will then go on to examine the effect of diffusing boundaries on the frequency and density of modes. In particular, it will examine the effect of the scale of the diffuser on its efficacy in this task. For ease of visualisation this will be done using a two dimensional model and, for accuracy a finite element, element simulation. The effect of going to three dimensions on the results will also be discussed. Finally, the effect of absorption based diffusing boundaries will be examined.
Low-frequency response in active acoustic practice rooms
Authors: Freiheit Ronald
Published: May 2008

Integrating active (virtual) acoustics into relatively small practice rooms to create a sense of envelopment is critical to the satisfaction of the musicians using these spaces for learning. The number of speakers and their locations play an important role in minimizing the ability to localize to the sources supporting this sense of envelopment. Equally important is the frequency response required for the speakers used in these applications, to more accurately simulate the acoustics of a performance environment. Excessive high frequencies increase the ability to localize and decrease the sensation of a larger space, since the air in larger spaces naturally absorbs many high frequencies. Another challenge is creating the sense of envelopment for instruments in the bass region (125Hz octave band and below) by providing enough low-frequency energy response. Work will be presented on low-frequency response desired to satisfy a sampling of solo cello players using active acoustic practice rooms. The optimal sources for these low frequencies - single or multiple - will be discussed. Updated information will also be provided on the sound field coverage in active rooms with extended low-frequency response.
The acoustics of the Beijing National Grand Theatre of China
Authors: Schmich Isabelle , Chervin Paul , Xiangdong Zhu , Xiang Yan , Guo-Qi L
Published: May 2008

The National Grand Theatre of China opened in December 2007 in Beijing. It is a complex of three performance halls: the Opera (2400 seats), the Concert Hall (2000 seats) and the Theatre (1100 seats). These three halls are covered by a super-ellipsoidal shell made out of titanium and glass. The history of the acoustic design evolution from the winning of the competition in 1999 by the Architect Paul Andreu to the final construction will be retraced including the preliminary design, the acoustic simulations and auralisations. The acoustic design of each hall will be presented with its specifications and detailed particularities. Final acoustic measurements have been done in the three empty halls and in the occupied concert hall. The results and acoustic criteria will be discussed. In addition, a subjective evaluation has been done with psychoacoustic questionnaires and the results will be presented and analysed.
Subjective Assessments of Acoustical Environments for Un-assisted Traditional Peking Opera Performances
Authors: Chiang Wei-Hwa , Lin Wei , Yu Ya-Jhen
Published: May 2008

The prevalence of Western performing arts has impacted on how traditional Peking opera is performed. It is, however, necessary to preserve and pass on traditional Peking opera for it integrates the essence of Chinese opera. The research has been conducted regarding subjective assessment of the acoustical environment for traditional Peking opera. Recording of dry sound sources was also performed. Sound strength and listening direction were found to be the principle factors that determined evaluation for overall impression while reverberation time is less important. The 6000 m3 can be used as the upper limit for room volume when a thrust stage is used.
Passive acoustic detection of grouper sound production
Authors: Mann David , Locascio James , Schärer Michelle , Koenig Chris , Nemeth Michael , Nelson Misty , Coleman Felicia , Appeldoorn Richard
Published: May 2008

Passive acoustic recordings were used to study the behavior of red hind (Epinephelus guttatus) at spawning aggregation sites off of Puerto Rico and Mona Island, and goliath grouper (Epinephelus itajara) and red grouper (Epinephelus morio) on the West Florida Shelf. The sounds produced by each species were unique, low-frequency pulsed sounds and associated with reproductive-related behavior. Male red hind produced sounds composed of a series of pulses that graded into a tonal-like sound, mostly during territorial patrolling. Long-term acoustic recorder (LARS) data from the west coast of Puerto Rico and Mona Island showed similar diel periodicities of sound production of red hind, but had different monthly peaks in sound production. Goliath grouper sounds consisted of low-frequency individual pulses (50-100 Hz) that are consistent with sounds produced by a large fish, and showed lunar periodicity in sound production. Peaks in sound production occurred nightly after midnight, but sounds were also produced throughout the day. Sound production and spawning by red grouper was recorded using a remotely operated vehicle (ROV) at depths of 80-100 m. Passive acoustic techniques can provide synoptic, long-term time series of sound production associated with reproductive activities of soniferous species at widely spaced sites.
Long-term Passive Acoustic Monitoring of Delphinids in the Southern California Bight
Authors: Soldevilla Melissa S. , Hildebrand John A. , Wiggins Sean M. , Roch Marie A.
Published: May 2008

Spectral characteristics of clicks are described for five species of delphinids in the Southern California Bight (long-beaked common dolphins, Delphinus capensis, short-beaked common dolphins, Delphinus delphis, Risso's dolphins, Grampus griseus, Pacific white-sided dolphins, Lagenorhynchus obliquidens, and bottlenose dolphins, Tursiops truncatus). Recent technological advancements allow long-term, broadband (100 kHz bandwidth), passive acoustic monitoring from autonomous sea-floor mounted instruments. The ability to record higher frequencies allows study of a broader range of odontocete vocalizations including echolocation clicks. To determine whether delphinid species could be identified by their clicks, concurrent ship-based visual and acoustic surveys were conducted. We find that clicks from Pacific white-sided and Risso's dolphins contain spectral peaks and notches that are unique and consistent for each species. These spectral patterns are also apparent in long-term autonomous acoustic recordings throughout the Southern California Bight. Utilizing this spectral classification method, we examine of diel, seasonal, and habitat use patterns of acoustically active Risso's and Pacific white-sided dolphins. The ability to monitor animals through the night provides insight into distinct diel patterns of acoustic activity for both species while the high temporal resolution acoustic data can be used to relate oceanographic time series to dolphin activity.
Detection and classification of call types in the vocalizations of north-east pacific blue whales
Authors: McLaughlin Jack , Josso Nicolas , Ioana Cornel
Published: May 2008

Characterization of marine mammal vocalizations is an essential part of any program of marine mammal monitoring as well as being of great help for furthering understanding of subjects such as underwater communication, sonar, etc. The vocalizations of the North-East Pacific (NEPAC) blue whales are known to be made of at least three different call types: the A call, the B call and the C call. This study aims at the development of a wholly automatic process of detection and classification for the two most common call types of the NEPAC population which are the A call and the B call. We created one template for the A call and one for the B call in order to extract features with matched filtering operations. We show that a simple Gaussian Mixture Model classifier can be used to accurately track and identify the call types in 24-hour long records. The proposed methodology is applied to real data sets recorded by seismic sensors.
Effect of ocean sound speed uncertainty on matched-field geoacoustic inversion
Authors: Huang Chen-Fen
Published: May 2008

The effect of ocean sound speed uncertainty on matched field geoacoustic inversion is investigated using data from the SW06 experiment along a nearly range-independent bathymetric track. Significant sound speed differences were observed at the source and receiving array and several environmental parameterizations were investigated for the inversion including representing the ocean sound speed at both source and receivers with empirical orthogonal function (EOF) coefficients. A GA-based global optimization method was applied to the candidate environmental models. Then, a Bayesian inversion technique was used to quantify uncertainty in the environmental parameters for the best environmental model, which included an EOF description of the ocean sound speed.
Quantifying the uncertainty of geoacoustic parameter estimates in a dynamic environment using oceanographic data
Authors: Chapman Ross , Jiang Yong-Min
Published: May 2008

This paper presents results of Bayesian matched field geoacoustic inversion in a temporally and spatially varying shallow water environment. The acoustic data were collected by a vertical line array at ranges of 1, 3 and 5 km in the SW06 (Shallow Water 06) experiment carried out in August 2006. The sound speed profiles measured at the array and at the source positions during the experiment showed significant variation in the thermocline in the middle part of the water column. The resulting uncertainty in the sound speed profile in the water impacts the performance of matched field inversion methods in estimation of geoacoustic model parameters. In previous work, an effective sound speed profile was estimated in the inversion, based on empirical orthogonal functions (EOFs) derived from a limited number of sound speed profiles measured at the time of the experiment. This paper explores the effect of using a larger number of profiles measured over several days in the SW06 experiment to include a greater diversity of ocean conditions in generating the EOFs. The inversion results for the two approaches are compared in terms of marginal probability distributions of the estimated geoacoustic parameters. (Work supported by Office of Naval Research).
Ultrasound and microbubble interaction
Authors: De Jong Nico
Published: May 2008

Ultrasound contrast agent (UCA) bubble response to ultrasound (US) is still the subject of several studies, since it determines the power of medical diagnostic imaging modalities. Generally, bubbles are studied using optical or acoustical methods, both having their specific advantages, in an environment that mimic the clinical practice as good as possible (small-diameter capillaries, red blood cells, blood viscosity). Acoustical observations could provide a better insight in the acoustical scattering of bubbles, which determines the final efficacy of contrast-enhanced diagnostic US imaging, and are better suitable to determine the properties of populations of bubbles. Optical observations allow for easier characterization of fewer bubbles and a more detailed characterisation in case where bubbles vibrate non spherically, which is expected for bubbles nearby a wall or red blood cells. In this presentation, we show optical recordings of the various bubble responses with the ultrahigh speed Brandaris-128 camera, and discuss the clinical implications of our findings.
Secondary Bjerknes forces between ultrasound contrast agent microbubbles
Authors: Versluis Michel , Garbin Valeria , Dollet Benjamin , Van Wijngaarden Leen , De Jong Nico , Lohse Detlef
Published: May 2008

Acoustic radiation forces arise on UCA microbubbles from pressure gradients in the ultrasound pressure field. The ultrasound wave emitted by an oscillating UCA microbubble and experienced by a neighboring bubble results in the so-called secondary Bjerknes force. Typically, only the (time) averaged value of the secondary Bjerknes force is estimated from experiments. Here, the ability to resolve in time the radial dynamics of UCAs and the evolution of their relative distances, allows us to obtain a quantification of the instantaneous secondary Bjerknes force. Two bubbles were selected and confined within two separate optical traps and positioned away from the sample chamber wall prior to insonation. The radius-time curves and distance-time curves were then extracted from high-speed optical recordings. The camera fully resolved the alternating attractive-repulsive features of the secondary Bjerknes force in time. The effect of the time averaged secondary Bjerknes force results in a net attraction of the two bubbles, with a typical observed displacement of 1-2 μm, with an instantaneous peak value of the secondary Bjerknes force of up to 10-6 N. We predict the mutual interaction of the two coated bubbles in their translation with an accuracy better than 10%.
Ultrasound contrast agents: from concept to clinical use
Authors: Tranquart François , Bouakaz Ayache , Bleuzen Aurore , Palanchon Peggy , Correas Jean-Michel
Published: May 2008

Contrast ultrasound imaging techniques are of interest for almost every clinical application in all organs including not only liver and kidney but also superficial organs and brain or lungs. This technique is mainly powerful in terms of lesion detection and characterization especially for liver with diagnostic value greater than 90%. This was the case for all categories of lesions (with values nearly 100% for liver metastases, FNH) but the accuracy was slightly lower for HCC. Specific recommendations were established by EFSUMB for the use of contrast agents in liver, pancreas, kidney, trauma and brain imaging for a proper and safe use to improve diagnosis accuracy. On the other hand, contrast-enhanced ultrasound may be used in evaluating response to therapy. The follow-up of vascularization under specific targeted treatments offers the capacity to early diagnose positive or negative local response for an adaptation of therapeutic way before or in absence of tumour size changes. This non invasive method could be repeated without adverse events early after starting this therapy in order to depict local response or recurrence for a better adaptation of dose with a strong impact on cost and limitation of adverse events.
Uncertainty of Acoustical Material Characteristic Measurements
Authors: Gerges Samir N. , Giesbrecht Peter K.
Published: May 2008

The experimental determination of the acoustic properties of sound absorption materials depends on numerous factors. The accuracy level in the determination of each property depends, for example, on the measurement apparatus and the type of material. The objective of this work is to present a study about the main sources of uncertainty in the measurement of properties such as sound absorption coefficient, acoustic impedance, flow resistivity and porosity. The uncertainties of the measurement apparatus of each property are quantified. The uncertainty of the materials heterogeneity is also assessed and its individual contribution highlighted. Important aspects of the Standards ASTM C 522 and ISO 10534-2, which present, respectively, recommendations and a procedure for flow resistivity and sound absorption measurements, are discussed. The methodology to calculate the uncertainty of each property is discussed with emphasis on the relevancy of each uncertainty source.
Design and implementation of a three-dimensional seven microphone vector intensity probe with low and high frequency compensations
Authors: Miah Khalid , Hixson Elmer
Published: May 2008

A seven microphone vector intensity probe has been designed and implemented in this report with low and high frequency compensations. Measurements from plane wave tube and anechoic chamber are used for overall system calibration with corrected gain and phase mismatch errors. Measured and calculated intensity level from both plane wave tube and anechoic room settings showed close agreement with each other in comparison to separate low and high frequency components of the array. Particle velocity vectors and pressures determined for calculating intensity were also used to calculate sound power and total energy density components of various sources. This microphone array vector intensity probe is then used to explore various sound source identification and localization problems.
Inspection of complex components with flexible phased array transducer
Authors: Casula Olivier , Toullelan Gwenael , Dumas Philippe
Published: May 2008

Non destructive testing techniques using ultrasonic methods are often carried out in contact. But, the inspection performances are limited to regular surfaces. Thus, surface irregularities lead to thickness variations of the coupling layer that result in beam distortions and losses of sensitivity. In the context, CEA/LIST has designed flexible phased-array techniques for compensating the surface irregularities and fitting the surface. The independent piezoelectric elements composing the radiating surface are mechanically assembled to build an articulated structure. An embedded profilometer measures the local surface distortion allowing to compute the optimized delay laws and to master the characteristics of the focus beam. Those delay laws computed by the UT-acquisition system are applied in real-time to the piezoelectric elements. To evaluate inspection method capabilities, CEA/LIST develops a simulation software for non destructive testing, CIVA, able to simulate realistic configurations in particular with complex 2D and 3D applications. Matrix flexible phased-array probes have been designed and manufactured in collaboration with IMASONIC. This paper sums up examples of inspections in complex geometries where these flexible probes have been successfully used. Moreover, the data are reconstructed thanks to CIVA tools and allow to locate and size the flaw in the part.
A psychoacoustical investigation into the effect of wall material on the sound produced by lip-reed instruments
Authors: Whitehouse James W. , Sharp David B.
Published: May 2008

In order to investigate whether a lip-reed instrument's material of manufacture plays a significant role in determining the timbre of the notes it produces, tests have been conducted on five post horns. These post horns have identical geometry but are manufactured from different copper alloys. Using a laser Doppler vibrometer, the structural resonances of each instrument have been established and the wall vibrations induced in each instrument when artificially blown have been measured. In this paper, these measurements are compared with findings from a series of blindfold playing tests carried out using professional musicians and with listening tests comprising notes produced by the different instruments.
Characterisation of brass musical instrument designs using the brassiness parameter
Authors: Myers Arnold
Published: May 2008

Recent work has established a "brassiness" parameter as a measure of the support given over the sounding length of a brass instrument to non-linear propagation in sound production. This parameter is a function of the geometry (bore profile) of an instrument, and provides a useful means of relating the timbral characters to the designs of the various kinds of brass instrument. The geometries of over 1000 brass instruments belonging to museums worldwide and to individual musicians have been measured to determine the values of their brassiness parameter. Comparisons of these enable not only a more precise taxonomy but also provide a tool for studying the evolution of instrument design. This paper explores both the taxonomic analysis of the whole brasswind field and also gives examples of the use of brassiness in historical research.
The modern violin bow in off-string action
Authors: Guettler Knut
Published: May 2008

The convex camber of the modern Tourte-model bow permits off-string stroke techniques to be performed with resulting clean and crisp attacks. This paper discusses how different bow-, string-, and bowing parameters must combine in order for this to be achieved. Of particular interest are the geometrical changes imposed on the bow stick during bouncing strokes. A good spiccato bow is characterized by a stick that feels "lively", even when the bouncing is low or the hairs are not leaving the string at all. With lesser-quality bows the player has to work harder (on the lower-pitched double bass even sometimes synchronously "shake" the bow stick in the string-length plane) in order to induce sufficient stick oscillation. Included in this study are measurements of finger action on bow sticks of different quality.
Numerical investigation of the effect of nonlinear propagation distortion on helicopter noise
Authors: Menounou Penelope , Vitsas Panagiotis
Published: May 2008

Nonlinear propagation distortion causes energy to be shifted to the high frequency end of the spectrum. This leads to underestimation of the noise levels at high frequencies. The effect has been demonstrated in the case of aircraft noise, but less attention has been given to helicopters. In the present work, the effect of nonlinear propagation distortion on helicopter noise is demonstrated based on measured data for low-speed descent and numerical calculations that predict the noise level away from the helicopter with and without nonlinear effects. It is shown that (i) for some frequency bands the difference between linear and nonlinear calculations can be as high as 8 dB, (ii) frequencies between 1000 and 3000 Hz are more affected, and (iii) the effect is highly directional depending on the receiver location around the helicopter. It is further shown that nonlinear effects manifest themselves differently than in the case of aircraft noise and that they depend on the specific helicopter noise mechanism. More specifically, the following helicopter-specific noise source types are investigated with regards to nonlinear effects: advancing Blade Vortex Interaction (BVI) noise vs retreating BVI noise, High Speed Impulsive noise, and BVI vs Very Impulsive noise.
Direct aeroacoustic simulations based on domain decompositions
Authors: Utzmann Jens , Munz Claus-Dieter
Published: May 2008

For CAA, an accurate and feasible direct simulation that considers both the generation of sound within the flow and its propagation into the far-field is hard to realize with one numerical method in a single computational domain. On the other hand, a direct approach contains automatically the interaction of the acoustic perturbations with the flow-field, a property which lacks the popular acoustic analogy models. The proposed method is basically a direct simulation, but it simplifies the problem that has to be solved for individual regions in the computational domain. The idea is to use a non-overlapping domain decomposition method where the equations, methods, grids and even the time steps are adapted to meet the local requirements. Inside the coupling framework, high-order solvers from different classes of methods are available: On unstructured grids, a reconstructed ADER finite volume method (ADER-FV) is used for linear and nonlinear problems, as well as a discontinuous Galerkin method. On structured grids, the ADER-FV and the ADER-FD method are efficiently implemented for nonlinear (FV) and linear (FV, FD) problems. These high-order accuracy methods ensure excellent wave propagation capabilities throughout the entire computational domain. In the subdomains, the Navier-Stokes, Euler and the linearized Euler equations are solved.
Asymptotic expressions for the directivity of round jets
Authors: Musafir Ricardo E.
Published: May 2008

Expressions for the directivity of round jets, in the high and low frequency limits, are derived, based on solutions of Lilley's equations. Two different forms of the equation in what concerns source terms representation are considered, along with general point sources of the appropriate type (i.e., equivalent stress and force sources and also, when necessary, volume sources), which are assumed to be statistically axisymmetric. Effects of mean shear and temperature gradients are accounted for, as well as of source movement. The expressions are compared with earlier ones, based on a plug flow model. The differences in the resulting expressions due to the choice of source description, which are relevant for hot jets, are discussed and used to derive a form consistent with both representations. Comparison with experimental data is also presented.
Investigations of roughness-generated TBL sound using coupled physical-computational experiments in conjunction with theoretical development
Authors: Blake William , Kim Ki-Han , Goody Michael , Wang Meng , Devenport William J. , Glegg Stewart A.
Published: May 2008

Sound produced by turbulent-boundary layers (TBL) over rough walls is being studied in a series of physical-computational experiments. At issue is the development of a knowledge of how the wall elements generate flow dipoles which directly determines how the sound is described in terms of dependent variables. The considered mechanisms include dipoles at the roughness elements due to their shed wakes, distributed surface dipoles due to convecting turbulence impinging onto elements, Rayleigh-like scattering into sound of aerodynamic pressures of hydrodynamic wave numbers of flow above the roughness. The LES of rough-wall TBL consists of "numerical" experiments being used to isolate the separate mechanisms. These simulations are benchmarked with analysis and with matching physical experiments on rough wall patches in which identical geometries of wall roughness and identical Reynolds numbers are used. In the physical measurements, array-based measurements of the radiated sound are being used to characterize the directivity and magnitude of the sound and to relate the sound to aerodynamic wall pressure and to classical characteristics of the turbulent boundary layer. The LES produces comparison for both radiated sound and detailed flow structure around the roughness elements. This project is funded by the Office of Naval Research, Washington, D.C., USA.
Modeling of sound propagation in nonuniform waveguides
Authors: Bi Wenping , Pagneux Vincent , Lafarge Denis , Aurégan Yves
Published: May 2008

Sound propagation in waveguides is modeled by a Multimodal Method. The waveguides geometries may involve bends, variable cross-sections, or their combinations. The waveguide boundaries may involve axially or circumferentially nonuniform impedance conditions or acoustically rigid conditions. Uniform flow may also be included for a simple uniform geometry. The pressure (displacement potential for uniform flow) is expanded in terms of the modes of acoustically rigid waveguides and an additional function that carries the information about the impedance boundary. The rigid waveguide modes and the additional function are known a priori so that calculations of the true modes of waveguides with impedance boundary, which are difficult, are avoided. By matching the pressure and axial velocity (displacement potential and axial derivative for uniform flow) at the interface between different axially uniform segments, scattering matrices are obtained for each individual segment; these are then combined to construct a global scattering matrix for multiple segments. After calculating the scattering matrix, the transmitted and reflected sound fields or intensities may be obtained for any kind of modal sources. The method allows modeling sound propagation in waveguides with axially and circumferentially nonuniform impedance boundaries up to dimensionless frequency K=70 in just hours on a personal computer, which advantageously compares with other techniques.
Acoustic PIV: Measurement of the acoustic particle velocity using synchronized PIV-technique
Authors: Fischer André , Sauvage Emilie , Roehle Ingo
Published: May 2008

This paper outlines a technique for measuring the acoustic particle velocity and the flow field simultaneously by applying synchronized particle image velocimetry (PIV). As test set-up a squared acrylic glass chamber was chosen. One side of the test section is connected to a loudspeaker, which allows a sinusoidal excitation of the chamber. To point out constrains of this method the investigation includes an analysis of excitation amplitude and frequency as well as the effect of the mean flow magnitude. Therefore a small PC fan can be mounted inside the test section to produce an adjustable mean flow. It can be shown that for a low number of averaged images (80) reasonable results can be achieved up to a certain level of fan rotation speed. Beyond this level the turbulence sensitivity increases and more images are necessary for the calculations. However, the acoustic particle velocity can be computed in the presence of turbulent flow. The presented method called acoustic PIV is a non intrusive technique, applied successfully in measuring acoustic particle velocity fields over a wide range of conditions.
Low speed exterior vehicle voise and the effect of pavement type
Authors: Donavan Paul
Published: May 2008

For operating conditions of cruise and moderate acceleration, the exterior noise emission of light vehicles is typically dominated by tire/pavement noise at speeds of 50 km/h or greater. At a test speed of 56 km/h, it has been found that pavement type can create a 10 dB or more variation in tire/pavement noise. This has significant implications for both community noise and vehicle noise emission testing. In this paper, the results tire/pavement noise measurements for over 40 different pavements in Europe and the United States are reported. These pavements include research surfaces, existing roadways, and ISO 10844 passby test surfaces. Measurements were conducted using an on-board sound intensity methodology that has been correlated to cruise-by noise levels. These results are discussed in terms of the revisions being considered for the newly revised ISO 362 passby test procedure and the ISO 10844 test surface specification. Additionally, a case history of community traffic noise reduction achieved by use of a quieter pavement is reviewed to demonstrate the importance of the pavement in low speed vehicle noise emissions.
Vehicle exterior noise from the view point of new experts
Authors: Schulte-Fortkamp Brigitte
Published: May 2008

The combination of physical and psycho- acoustical measurements with scientific evaluation of perceptual responses to environmental noise, known as Soundscaping, is an essential method for assessing and actualizing environments. Empirically, the perception of sounds and their evaluation will be explored under the premise of combining human judgment and physical factors. In a recent Soundscape Project, environmental noise perception and evaluation in a defined urban area were investigated in detail. Classical measurements and open, narrative, but issue-centred interviews with residents were carried out, and those interviews allowed the interviewed persons to set their own focus on certain aspects concerning the development of a public space in Berlin. Method and procedure will be discussed in detail to introduce to the New Expert Concept. The Soundscape Project is a module of the Project "Nauener Platz - Remodelling for Young and Old" in the framework of the research program "Experimental Housing and Urban Development (ExWoSt)" of the "Federal Ministry of Transport, Building, and Urban Affairs (BMVBS)" by the "Federal Office for Building and Regional Planning (BBR)". It is related to the fields of research (ExWoSt) concerned with "Innovation of Urban Neighbourhoods for Families and the Elderly". The project executing organization is the Regional Office Berlin-Mitte.
Noise Mapping and Noise Scoring - Software Techniques and Result Presentation
Authors: Probst Wolfgang
Published: May 2008

Noise scoring is based on noise level maps and on exposure distribution. Different techniques can be used to develop the areal distribution of these values and to present them as coloured maps. Especially more complex ratings that are not only based on an exposure level and on population densities need relatively complex procedures to develop them from noise maps. It must be taken into account that there are two important steps in this procedure: One is the calculation of the noise score itself and the other is the presentation as coloured map to detect and focus on Hot Spots. Different techniques have been developed, were integrated in the software and have been applied in the frame of the QCity project. The consequences of different parameter settings are presented and discussed. The second step is the assignment of colours to a given scale of result values and even this simple process must be handled carefully to transport the needed information.
Budapest Noise Mapping Project II. - Results
Authors: Berndt Mihály , Muntag András
Published: May 2008

The Hungarian capital Budapest, and their agglomeration have recently finished their first strategic noise map. According to the Hungarian noise regulations and to the European Directive 2002/49/EC, this is a legal obligation. The main part of the costs was supported by the EU. The preparation of the strategic noise maps based on a computer model and describing the present noise situation of the municipalities, should be seen as the first step to build a true noise information and management system, based on the computer model initially developed. The main parameters of the project were the planned area 1100 qkm, number of dwellings 440 thousand, length of the mapped roads ca. 2000 km This paper is based on the experience of 23 municipal noise maps - Budapest and other 22 settlements in the agglomeration. We successfully finished the project on time - the results (all maps) can be found on the internet-page: http://terkep.budapest.hu/website/zajterkep The second paper shows the results of the project.