bluuebunny/crossref_metadata_2025 huggingface dataset:
On the relevance of impact source impedance at low frequencies
Authors: Zeitler Berndt , Schoenwald Stefan , Gover Brad
Published: May 2013

Many researchers have posed the question of whether the standard tapping machine simulates the impedance of real sources well enough to properly judge the impact sound insulation performance of a floor. Proposed solutions such as the modified tapping machine, the bang machine, and ball were results of these investigations. Recent data collected on bare (wood and concrete) floors, suggest that in the low frequency range, the impedance of the source has no influence on the power injected into the floor. This is presumably due to the fact that the bare floors have much higher impedances than most common sources, meaning only the blocked force of the source influences the injected power. This furthermore suggests that modifying or redeveloping the source is not necessary, and that through use of an appropriate weighting curve a single number rating that correlates well with subjective measurements can be defined. Supporting objective and subjective results will be presented.
Impact noise isolation provided by a bare concrete slab evaluated according to European and American regulations and two prediction software compared to field measurements
Authors: Lévêque Nicolas
Published: May 2013

European regulation EN12354-2:2000 outlines a procedure to predict impact noise isolation provided by a floor covering installed on a concrete slab. In Annex B of this regulation, one can found a formula to calculate the Normalized Impact Sound Pressure Levels (NISPL) for a bare concrete slab. In North America, ASTM 2179-03 standard describes a procedure to measure impact noise insertion loss provided by a floor covering in laboratory conditions, using NISPL of a reference bare concrete slab. INSUL software uses Cremer's point force excitation theory to evaluate NISPL of concrete slab whereas BASTIAN software uses the procedure described in EN12354-2:2000 European regulation. This paper presents a comparison between NISPL calculated for 8 to 10 inches thick bare concrete slab according to procedures and software listed above and field NISPL measurements of thirty-five bare concrete slabs varying in thickness from 8 to 10 inches presented in a article published in the Journal of Canadian Acoustical Association [Morin (2009)]. This comparison suggests that a statistical approach is required to evaluate accurately NISPL provided by a floor covering installed on a concrete slab according to the procedures and software listed above.
Anthropogenic noise constrains acoustic communication in urban-dwelling frogs
Authors: Parris Kirsten M.
Published: May 2013

Urban noise may hinder acoustic communication in a diversity of animal groups by reducing the distance over which vocal signals can be detected. Given the importance of such signals for mate attraction and territory defence, this acoustic interference may have wide-ranging consequences for individual fitness. I will present a mathematical model of the active space of frog calls in urban noise as a function of body size. Despite having lower auditory thresholds, larger species with lower-frequency calls are predicted to suffer the greatest reduction in communication distance in noisy urban environments. During a field study in Melbourne, Australia, my colleagues and I found that the southern brown tree frog Litoria ewingii called at a higher frequency in traffic noise. However, modeling indicates that the observed frequency shift would confer only a modest increase in active space. Furthermore, as females of certain frog species appear to prefer lower-frequency advertisement calls, this strategy may improve the audibility of calls but reduce attractiveness to potential mates. Calling more loudly would result in a larger increase in active space, but the high metabolic cost of this strategy could limit chorus tenure and ultimately reduce breeding success.
Are there metabolic costs of vocal responses to noise in marine mammals?
Authors: Holt Marla M. , Dunkin Robin C. , Noren Dawn P. , Williams Terrie M.
Published: May 2013

Many species respond to increases in environmental noise by increasing the amplitude, duration, and/or repetition rate of their vocalizations. Potential costs of noise-induced vocal modifications include increased energetic costs but no empirical data in marine mammals exist. This study’s objective was to compare the metabolic costs of communicative sounds produced by captive bottlenose dolphins (N = 2) under two conditions (low- and high-amplitude vocalization trials) to assess energetic costs of vocal responses to noise. An experimental trial consisted of a 10-min rest period to determine resting metabolic rate, followed by a two-minute vocalization period, and concluded with another 10-min rest period to measure recovery. Open-flow respiratory was used to measure oxygen consumption during each trial component. Vocalizations were recorded using a calibrated hydrophone for analysis. Both dolphins tended to produce longer vocalizations during high-amplitude trials. Thus, metabolic rates were related to total sound energy of all vocalizations produced during the vocal period for each trial. Metabolic costs tended to be higher during high sound energy trials, but only verged on statistical significance when vocal-performance differences were at least 10 dB (in cumulative sound exposure level). This study provides key data to assess biological consequences of anthropogenic noise exposure in marine mammals.
Benign exclusion of birds using acoustic parametric arrays
Authors: Dieckman Eric A. , Skinner Elizabeth , Mahjoub Ghazi , Swaddle John , Hinders Mark
Published: May 2013

Excluding birds from areas can be important in aviation safety, agriculture, and facilities maintenance. Presenting audible stimuli or predator vocalizations in the affected area often has initial success, but has a limited effect over the long-term, even if the signals are varied to reduce the chances of the birds habituating to the sounds and objects. Many birds are highly vocal and rely on auditory communication in almost every aspect of their life history. By creating noise specifically targeted to be within the vocal range of the nuisance species, we hypothesize that the birds will be less able to communicate and will move to more acoustically suitable environments. To avoid introducing noise pollution to the surrounding environment we create spatially well-controlled “sonic nets” using a mix of speakers and acoustic parametric arrays. To better understand the interaction of the sound field and the environment we combine finite difference solutions of the KZK equation with 3D acoustic finite integration simulation. These simulations allow us to propagate a nonlinear acoustic beam to a real-world target and then study the scattering from the target. We discuss initial experiments with a parametric array in an aviary on the exclusion of starlings from a food source.
In situ measurement of the individual target strength of crustacean zooplankton with concurrent optical identification
Authors: Briseño-Avena Christian , Jaffe Jules S. , Roberts Paul L. , Franks Peter J.
Published: May 2013

Acoustic methods are common tools in the study of zooplankton distributions and behaviors. However, relating acoustic scattering to zooplankton abundance is difficult because zooplankton acoustic properties have been challenging to obtain in situ. Most of the acoustic measurements of zooplankton come from either preserved or recently dead organisms, or are derived from computer models. Other attempts to measure in situ acoustic target strength (TS) of zooplankton have targeted larger taxa such as euphausiids and amphipods. In situ measurements of copepods and other small crustaceans are extremely desirable as these taxa can be dominant in marine ecosystems. Here we present in situ measurement of TS using frequencies of 1.5–2.5 MHz with concurrent stereoscopic imaging. The concurrent calibration of the optics and acoustics permits the quantification of individual acoustic TS associated with the individual organism that gave rise to the echo. Furthermore, new technological advances have allowed us to measure organisms with TS as small as −125 dB. The results of this work will permit improvements in extant acoustic models, and enhance our interpretation of acoustic data collected in the field.
High-frequency quantitative ultrasound approaches for cancer detection in freshly-excised lymph nodes
Authors: Mamou Jonathan , Coron Alain , Saegusa-Beecroft Emi , Hata Masaki , Oelze Michael L. , Yanagihara Eugene , Yamaguchi Tadashi , Laugier Pascal , Machi Junji , Feleppa Ernest J.
Published: May 2013

Histology performed to assess lymph nodes excised during node-dissection surgeries from cancer patients suffers an unsatisfactory rate of false-negative determinations due to labor and time constraints. In this study, more than 300 lymph nodes were scanned in 3D using a 26-MHz high-frequency ultrasound transducer. Following scanning, individual nodes underwent a special histology procedure that involved step-sectioning each node at 50-µm intervals to guarantee that no significant cancer foci were missed. The 3D radio-frequency ultrasound dataset was analyzed using overlapping 3D regions-of-interests that were individually processed to yield 13 quantitative ultrasound (QUS) estimates associated with tissue microstructure and were hypothesized to show contrast between normal and cancerous regions in lymph nodes. Step-wise linear discriminant analyses were performed to yield an optimal QUS-based classifier. ROC curves and areas under the ROC curves (AUCs) were obtained to assess cancer-detection performance. The AUC for the linear combination of four QUS estimates was 0.83 for a dataset of 110 axillary nodes of breast-cancer patients. Similarly, using five QUS estimates, an AUC of 0.97 was obtained for a dataset of 180 nodes of gastrointestinal-cancer patients. These studies demonstrate that QUS methods may provide an effective tool to guide pathologist towards suspicious regions in lymph nodes.
A method to validate quantitative high-frequency power Doppler ultrasound with fluorescence in vivo video microscopy
Authors: Lacefield James C. , Pinter Stephen Z. , Kim Dae-Ro , Hague M. Nicole , MacDonald Ian C. , Chambers Ann F.
Published: May 2013

Flow quantification with high-frequency power Doppler ultrasound can be performed using the wall-filter selection curve (WFSC) method [Elfarnawany et al., Ultrasound Med. Biol. 38, 1429–1439 (2012)]. The WFSC method plots color pixel density (CPD) as a function of wall filter cut-off velocity as a means of objectively selecting an operating point cut-off velocity. In this study, an in vivo video microscopy (IVVM) system was used to measure the size of small (140–400 μm diameter) mouse testicular vessels immediately after the vessels were imaged with 30 MHz power Doppler. The mouse remained on the same platform throughout ultrasound and IVVM imaging. Measurements in four image planes from three mice demonstrated that, similar to previously reported flow-phantom data, in vivo WFSCs exhibit distinct, sloped “characteristic intervals” at cut-off velocities where the CPD approaches the gold-standard IVVM estimate of vascular volume fraction. A wide range of operating point cut-off velocities (4.5 to 12 mm/s) was obtained, which indicates that use of a predetermined cut-off can produce substantial errors in cross-sectional studies that employ power Doppler to quantify vascularity. The WFSC method is a promising strategy for adapting the cut-off velocity to intersubject and longitudinal variations in blood flow during microvascular imaging experiments.
Individual in-situ calibration of insert headphones
Authors: Hiipakka Marko , Pulkki Ville
Published: May 2013

An important procedure in binaural reproduction is the calibration of headphones, which is commonly achieved by first measuring the headphone transfer functions (HpTFs). The commonly used methods of measuring the HpTF are not applicable for insert headphones, since the inserts block the ear canal entrance and since the transducer ports of the inserts are inside the ear canals. Recently, an alternative technique of obtaining HpTFs of inserts using measurements with in-ear microphones, computational modeling, and electro-acoustic Norton-type source models of the inserts has been proposed. In this study, the technique is evaluated using measurements at the eardrums of eight human subjects and computational modeling with normal human ear canal parameters. In addition, different methods of obtaining the electro-acoustic source model parameters are compared. It is shown that the most reliable method of obtaining the Norton source parameters of insert headphones is through measurements with a miniature-sized particle velocity sensor and several tubes with different cross-sectional diameters as acoustic loads. The evaluations show that the proposed technique of obtaining the HpTFs of insert headphones is accurate and reliable at least up to 8 kHz, which bolsters the applicability of the technique for individual in-situ calibration in binaural reproduction.
A comparison of methods for measuring the acoustic input impedance of ear canals for hearing aid applications
Authors: Sankowsky-Rothe Tobias , Köhler Simon , Blau Matthias , Stirnemann Alfred
Published: May 2013

In hearing aid fitting the sound pressure at the ear drum is a reference quantity, since all real ear characteristic values refer to it. Typically, the sound pressure at the ear drum is estimated by a model of an average ear canal (e.g., a coupler). Such a model cannot account for inter-individual differences. Alternatively, there are methods to predict the acoustics of the individual ear canal. Some of these methods make use of the acoustic input impedance of the ear canal. In general, the accuracy of the measured impedance depends on the effort that will be made. Therefore, different methods of impedance measurements were investigated concerning accuracy and effort. The methods differ in the number of calibration measurements (and calibration parameters). They were compared on the basis of impedance measurements on different model ear canals. Measurements were done with an impedance probe consisting of a typical hearing aid receiver and a hearing aid microphone. The measurements were compared to measurements with a reference impedance probe and method. As a result, it was observed that with a single calibration measurement the maximum absolute error of the transfer impedance was smaller than 3 dB up to 8 kHz.
A comparison of methods for estimating individual real-ear-to-coupler-differences in hearing aid fitting
Authors: Köhler Simon , Sankowsky-Rothe Tobias , Blau Matthias , Stirnemann Alfred
Published: May 2013

The sound pressure at the ear drum is the reference quantity for almost all applications of sound delivery to the ear, especially in hearing aid fitting. Since hearing aids are typically calibrated using the so called 2cc-coupler, the link to the individual sound pressure at the ear drum is given by the real-ear-to-coupler-difference (RECD). Nowadays, averaged RECDs are used for hearing aid fitting, which do not account for inter-individual differences in ear canal acoustics. As a consequence, resulting coupling errors may reach 15 dB for frequencies up to 10 kHz. Alternatively, there are methods for estimating individual RECDs, based on acoustic impedance measurements at the inner face of the ear mold. These methods differ in effort (e.g., the complexity of the ear canal model and fitting algorithm) and accuracy. By using an integrated ear canal microphone, individual RECD estimation could be feasible in future hearing aid fitting. In this research, six different methods to predict individual RECDs were compared using simulations as well as real ear measurements with open and closed ear molds. As a result, it appeared that relatively simple cylindrical and conical ear canal models give the best compromise between effort and accuracy.
Harmonic hydromechanical movement
Authors: Tieso Santos , Messina Francisco , Fantini Lucas V. , Casco Richiedei Nicolás , Cacavelos Nahuel , Talento Ignacio , Vallese Nicolás , Fernández Rodrigo , Saavedra Adrián
Published: May 2013

The current theoretical physics tools used to describe the acoustic phenomena that occur outside the ear, such as the specific impedance, the acoustic impedance and the mechanical impedance are not applicable to describe the cochlear mechanics. For this reason, this study uses the hydro-mechanical impedance concept. The latter is only applicable to a harmonichydro-mechanical systems, which consist of a rigid recipient, filled with liquid and two elastic windows that relate the system with a sound environment, considering that the distance between them should be much smaller than the sound wavelength. This system could be considered as the most primitive model inner ear to build. The movement of the contained fluid in this system has particular characteristics that differentiate it from the wave motion and from a simple mass-spring-dumping vibration system. In order to demonstrate the existence of the harmonic hydro-mechanical movement, was modeled and built an equivalent harmonic electrical system, which results corresponded with the ones from the theoretical mathematical model.
Secondary path variation in human listeners and its effect on an active noise cancellation system
Authors: Xiao Jinjun , Xu Buye , Zhang Tao
Published: May 2013

Active noise cancellation (ANC) has been applied to cancel the penetrated ambient noise in the ear canal for hearing impaired listeners [Zhang et al. (2012)]. The performance of the proposed ANC system depends on the characteristics of the secondary path (SP). In this study, we developed an in-ear ANC system where the error microphone and the miniature loudspeaker were both placed in the ear canal. In such a case, the SP response depends on the error microphone response, the loudspeaker response, and how the microphone, the loudspeaker, and the ear canal are acoustically coupled. A robust method was proposed to measure the SP response of the proposed ANC system under various coupling conditions using human listeners. Variations of the measured SP responses were analyzed both within each individual and across different individuals. The effect of the SP variations on the performance of the proposed ANC system was evaluated. The implications for improving the proposed ANC system will be discussed.
Effects of a boundary layer trip in the prediction of noise from flow past tandem cylinders
Authors: Armstrong Daniel , Mongeau Luc
Published: May 2013

The use of boundary layer trips in wind tunnel experiments forces transition to fully turbulent flow, which affects the resulting acoustic signature. Boundary layer trips are often too small to be modeled geometrically in computational simulations, making it difficult to consider their influence. The goal of this study was to determine the best method for representing the effects of a boundary layer trip in the benchmark aeroacoustic problem of flow over tandem cylinders in a wind tunnel. This case is pertinent to the study of aircraft landing gear noise because periodic vortex shedding results in pronounced acoustic tones in addition to broadband noise from turbulent wake interactions. A hybrid lattice-Boltzmann Method/Ffowcs-Williams Hawkings technique was used to predict the transient flow field and the resulting noise. This study compared four methods for simulating the trip's effects: (1) applying a surface roughness on the upstream cylinder; (2) reducing the viscosity of the fluid; (3) forcing velocity perturbations in the incoming free stream; and (4) applying a ridge to the upstream cylinder that is one volume element thick. Preliminary results have shown that reducing the fluid's viscosity is an effective way to reproduce the highly turbulent flow patterns and the acoustic signature.
Acoustic compressor coupled with fluidic diodes
Authors: Thomas Sonu K. , Muruganadam T. M.
Published: May 2013

Performance of an acoustic compressor coupled with a fluidic diode is studied. The acoustic compressor works on the idea of Resonant Macrosonic Synthesis (RMS) technology demonstrated by Lawrenson et al. The main idea is to replace non-return valves by no moving part fluidic device. Fluidic diode rectifies an oscillatory flow analogous to rectifying an electric AC to obtain DC output. Synthetic jets analogous to AC current falls in the category of jet-driven acoustic streaming, which has a zero mean mass flux. The synthetic jet can be combined with no-moving part fluidic device to generate Hybrid Synthetic Jets with non zero mean mass flux. Non-zero mass flow rate was achieved by coupling fluidic diode and the resonator. In the present study, better rectification is achieved by having number of fluidic diodes in series. Experiments were done for the case of 3 and 4 diodes in series. In the case of three diodes in series the mass flow was 4.6 l/min and in case of four diodes it was 4.9 l/min. Full paper will present the pressure and mass flow measurements for 1 to 5 diodes in series. Thus, RMS cavities with fluid diodes can work as a pump.
Analysis of vibroacoustics of trombone bells thanks to an adaptation of the Miller experiment
Authors: Gautier Francois , Secail Mathieu , Gilbert Joel
Published: May 2013

The influence of wall vibrations on the sound produced by a wind instrument is an open question. If it is clear that the vibrations of bells vibrations can be felt and measured, the influence of these vibrations on the radiated sound is more difficult to bring to light, because the fluid-structure couplings involved are particularly weak except when coincidence effects occur. We propose to study the case of a trombone bell, which is large and thin, favoring the vibrations of large amplitudes and thus the vibroacoustic coupling between the wall and the air column. For studying the light fluid-structure interaction in organ pipes, Miller [Science 29(735), 161–171 (1909)] developed one century ago an experiment consisting in blowing an organ pipe surrounded by water. A water tank can be filled progressively in order to modify the mechanical modes of the system in a continuous manner. We propose an adaptation of this experiment to the case of a trombone bell. The acoustic impedance, the acoustical and mechanical responses of a trombone bell excited by a loudspeaker or a shaker are measured for different levels of water allowing an analysis of the vibroacoustic couplings.
The soft-source impedance of the lip-reed: Experimental measurements and computational simulation
Authors: Newton Michael , Harrison Reginald Harrison , Kemp Jonathan
Published: May 2013

Most theoretical descriptions of the brass instrument lip-reed consider the acoustical condition at the lips to be a closed, rigid termination, corresponding to a unitary reflectance. This assumption is carried through to many computational models as well. In reality, the protrusion of the player's lips into the mouthpiece causes a periodic shortening/extension of the acoustical tube downstream, an effect sometimes but not always incorporated into such models. Of interest here is the absorption properties of the lip termination, the so-called “soft source impedance.” This provides a further modification to the boundary condition at the lips, since the soft, deformable nature of the lips are likely to cause some extra damping of the acoustic standing wave. Measurements are presented to demonstrate this damping effect using an artificial mouth. This is achieved through measurements of the lip reflectance from downstream of the lips, from where it is shown that the reflectance shows a dip at the peak absorbance frequency of the lips. The frequency of the absorbance is shown to vary as the lip parameters are changed. A simple computational model is described to account for the effect.
Influence of classroom acoustics on the vocal behavior of teachers
Authors: Astolfi Arianna , Carullo Alessio , Vallan Alberto , Pavese Lorenzo
Published: May 2013

Erroneous vocal behavior of teachers and their changes in the voice production due to poor acoustics in classrooms, can be investigated through recently developed voice-monitoring devices. These devices are portable analyzers that use a miniature contact microphone glued to the jugular notch in order to sense the skin acceleration level due to the vibration of the vocal folds. They estimate the Sound Pressure Level (SPL) at a certain distance from the speaker’s mouth, provided that a suitable calibration procedure is performed, the fundamental frequency and the time dose. Two different devices are compared in this work: the former is a commercial device, whose phonation sensor is a small accelerometer; the latter, recently developed by the authors, uses an electret condenser microphone to sense the skin acceleration level. SPL and fundamental frequency are estimated over 30 ms- and 50 ms-length frame and the results that refer to a sample of 40 primary school teachers and some university professors are analyzed. The length of the voice and pause frames is analyzed in order to detect the maximum of occurrence and accumulation in different conditions of noise and reverberation. A method for the detection and analysis of the emphatic speaking is also proposed.
The teachers perspective on noise in the classroom
Authors: Jaramillo Ana M. , Ermann Michael , Miller Patrick
Published: May 2013

A survey was sent to third grade teachers in Orange County, FL, to find out about their noise awareness and coping strategies. Results of the survey were also correlated to mechanical system type and achievement data. Preliminary analyses show very little awareness on mechanical noise by teachers but a good range of coping strategies when noise sources are present (mostly activity noise). The survey also helped to better understand the classroom environment. For example, most classrooms have a frequent use of computers or projectors and a few schools are still open-plan. These facts create new questions about noise in the classroom that need to be addressed in further studies.
Perception and evaluation of noise sources in open plan office
Authors: Pierrette Marjorie , Parizet Etienne , Chevret Patrick
Published: May 2013

Open plan offices are now the most common form of workspaces organization. They can improve communication between workers while saving space. Their main drawbacks are the lack of intimacy for occupants and the increase of noise level. Noise is one of the most important annoyance factor as described by workers (see SBISB study, 2010). This paper describes a study aiming at a better knowledge of most annoying noise sources in an open plan offices. It consisted in interviews and questionnaires conducted in offices together with physical measurement. This provided some information about sources and tasks for which workers are mainly disturbed. The analysis of recorded answers allowed to evaluate the influence of this annoyance on job stress and health and emphasize the influence of environmental and individual factors in the assessment of noise annoyance.
Work performance and mental workload in multiple talker environments
Authors: Ebissou Ange , Chevret Patrick , Parizet Etienne
Published: May 2013

The impairment of cognitive performance resulting from the presence of speech sounds is known to increase as the intelligibility of the speech signals is improved. For that reason, speech intelligibility measures are used to quantify the nuisance potential of an unattended voice. However, most of these indexes struggle with situations in which the level of the masking sound is fluctuating. This is the case in open-plan offices, where competing voices are involved. This paper relates a set of experiments in which subjects had to carry out a basic memory task in various noise settings. In addition to a target speech, the masking sounds were made up of speech and differed in temporal variability. The signal-to-noise ratios and the overall long-term spectra were kept constant. Disturbance was assessed both through objective measurements of performance and subjective reports of workload. The results highlight the importance of taking into account the temporal fluctuations of the overall ambient sound when trying to ascertain the influence of speech intelligibility on observed and perceived disturbance during the performing of a mental activity. Insights are provided, which could lead to the use of a speech intelligibility measure better equipped to deal with multi-sources environments.
Airborne sound insulation as a measure for noise annoyance
Authors: Neubauer Reinhard O. , Kang Jian
Published: May 2013

There is currently a lack of measure to describe airborne sound insulation in terms of subjective evaluation of noise annoyance. With a given sound insulation value, different kinds of sound signals could produce rather different hearing sensation levels. Physical noise measurements to describe airborne sound insulation often cannot solve problems in terms of noise annoyance, and psychoacoustic metrics are increasingly used. Recently, new results of evaluating sound insulation spectra by single-numbers have been adapted for practical applications such as in ISO 16717-1. In this paper, comparisons are carried out to demonstrate how single-number ratings are affected by non-steady-state sounds. The effect of a sound insulation having a frequency dip of 6 dB has also been examined. It is well known that noises with tonal components could be rather annoying, so that it would be of significance to examine if a frequency depending sound insulation can act as a filter for tonal components. In this paper, it will be shown that psychoacoustic magnitudes like loudness, sharpness, and fluctuation strength can largely account for different aspects, especially if airborne sound insulation is supposed to describe hearing sensation.
Noise reduction in working areas by the application of absorbing baffle-systems
Authors: Probst Fabian
Published: May 2013

Baffle systems are arrangements of absorbing panels that allow free flow of air and therefore do not disturb the acoustic climate. This is one of the reasons why they are often used in industrial environments because there is no need to take into account aspects of thermal isolation that may be a problem with closed suspended ceilings. A method to determine the absorption coefficient of baffle systems was derived and published in 2008 [Probst W.: “Sound absorption of baffle systems”, Lärmbekämpfung Nr.2 (2008)]. A method is now presented how such systems can be taken into account if the acoustic behavior of even complex rooms is determined by computer modeling. For simple cases, the mentioned analytical method can be applied, and it is shown that the results are in good agreement with the detailed simulation. But this detailed simulation allows to determine the acoustic influence of partially covered areas with different heights and otherwise complex layouts with absorbing appliances.
Experimental study on sound absorbing performance of rubber crumb
Authors: Borelli Davide , Schenone Corrado , Ilaria Pittaluga
Published: May 2013

The present paper describes an experimental campaign aimed at the determination of acoustical properties of vulcanized rubber crumbs obtained by the shredding of used tires. In particular, their performance as sound absorbing material in lined ducts has been investigated. The most innovative aspect that is addressed in the study is the use of a waste material such as rubber tires reduced into small grains as a sound absorbing material: tires are in fact usually used at the end of their life cycle as fuel and burned in cement kilns in order to take advantage of their high heating value, with all the problems of pollution that this solution produces. Two kinds of rubber crumbs have been investigated in terms of characteristic dimension of the grains, porosity, and sound absorbing coefficient, while their “in situ” performance when used inside lined and parallel-baffle rectangular ducts has been evaluated measuring their insertion loss. The results of this research show that the acoustical behavior of the tested rubber crumbs is the typical behavior of the granular materials, showing a noteworthy performance of the tested material in the low frequency range, opening a scenery of possible applications where noise has relevant tonal components below 315 Hz.
Shape optimization of reactive mufflers using threshold acceptance and finite element method methods
Authors: Khamchane Abdelkader , Khelfaoui Youcef , Hamtache B.
Published: May 2013

Recently, research on the acoustic performance of reactive mufflers under space constraint becomes important. In this paper, the attenuation performance of single and double expansion-chambers under space constraint is presented. To assess the reactive mufflers, a shape optimization analysis is performed using a novel scheme called threshold acceptance (TA), the best design obtained by the shape optimization method are analyzed by Finite Element Method (FEM). The numerical assessment is based on the maximization of the sound transmission loss (STL) using the Transfer Matrix Method (TMM), a modeling method based on the plane wave propagation model. The FEM solution used to analyze the STL of the shape optimized mufflers is based on the Acoustic Power method, a standard computational code COMSOL Multiphysics is used to analyse in 3D the sound attenuation of the mufflers by the FE method. The acoustical ability of the mufflers obtained is than assessed by comparing the FEM solution with the analytical method. Results show that the maximal STL is precisely located at the desired targeted tone. In addition, the acoustical performance of mufflers with double expansion-chamber is found to be superiors to the other one. Consequently, this approach provides a quick and novel scheme for the shape optimization of reactive mufflers.
Numerical mode-matching approach for acoustic attenuation prediction of expansion chambers with single inlet and double outlets
Authors: Ji Zhenlin , Fang Zhi
Published: May 2013

Numerical mode matching (NMM) method is developed to predict the acoustic attenuation performance of expansion chambers with single-inlet and double-outlets. The two-dimensional finite element method is employed to calculate the transversal eigenvalues and eigenvectors, and the mode matching technique is used to determine the modal amplitudes and transmission loss of expansion chamber silencers by combining the boundary conditions at inlet and outlets. For the purpose of validation, the transmission loss predictions of elliptical expansion chambers with single-inlet and double-outlets from the present NMM method and the three-dimensional finite element method (FEM) are compared, and good agreements between them are observed. Then the NMM method is used to investigate the effects of extended lengths and locations of inlet and outlets on the acoustic attenuation performance of elliptical expansion chambers.
Chaos and beyond in a water filled ultrasonic resonance system
Authors: Adler Laszlo , Yost William T. , Cantrell John H.
Published: May 2013

Finite amplitude ultrasonic wave resonances in a one dimensional liquid-filled cavity are reported. The resonances are observed to include not only the expected harmonic and subharmonic signals but chaotic signals as well. The nonlinear features of this system were recently investigated and are the focus of this presentation. An ultrasonic interferometer having optical precision was constructed. The transducers having the frequency range of 1–10 MHz, driven by a high power amplifier. Both an optical diffraction system and a receiving transducer were used to assess the generated resonance response in the cavity. At least five regions of excitation are identified: (1) Linear region: at low intensity of the ultrasonic wave the diffraction pattern of a light beam is symmetric. (2) Nonlinear region: with increased sound amplitude the diffraction pattern becomes asymmetrical. (3) Subharmonic region: further increase of the amplitude above a threshold value leads to the generation of subharmonics. (4) Chaos: increasing the drive amplitude to a second threshold level the diffraction pattern is smeared out indicating a time-chaotic region. (5) Beyond chaos: further increase of the amplitude results again a stable diffraction pattern. A first-principle-based explanation of the experimental findings is presented. [Work supported by the Aircraft Aging Program, at NASA Langley Research Center. Pending approving by NASA.]
Exploration of third-order nonlinear acoustics for projection of narrow-beam lower-frequency underwater beams
Authors: Koch Robert M. , Katz Richard A. , Pierce Allan D. , Hughes Derke R.
Published: May 2013

Projection systems are considered where two or three frequencies (e.g., f1, f2, and/or f3) are simultaneously projected into water in a parallel fashion. High near-field amplitudes produce beams of frequencies equal to any linear combination of f1, f2, and f3, with integer coefficients n1, n2, and n3 (possibly zero or negative). Interest here is in the case where the magnitudes of the coefficients sum to three, associated with a third-order nonlinearity. The question addressed is that of how large the amplitude of the far-field signal will be. The considered causes of the nonlinearities are (1) the convective derivative term in the total time derivative of the fluid velocity, and (2) the higher coefficients in the expansion of the fluid density in terms of the deviation of the pressure from its ambient value. These coefficients are derived from data reported by Holton et al. [J. Acoust. Soc. Am. (1968)] on the sound speed in water. A perturbation technique is explored starting with the basic nonlinear equations of compressible time-dependent fluid dynamics, where at each step one has a simultaneous set of coupled linear and homogeneous equations with the source terms dependent on the solutions of the analogous equations corresponding to the previously considered orders.
Numerical simulations of a transient behavior in the onset of thermoacoustic marginal oscillations in a looped tube
Authors: Shimizu Dai , Sugimoto Nobumasa
Published: May 2013

This paper simulates a transient behavior in the onset of spontaneous, thermoacoustic oscillations of a gas in a looped tube with a so-called stack sandwiched by hot and cold heat exchangers. Numerical simulations are performed to solve an initial-value problem by employing the linearized boundary-layer theory. Initial conditions are chosen in such a way that the gas under a uniform pressure is given impulses at two locations in the outside of the stack to cancel with each other. Because of installation of the stack and heat exchangers, account is taken of discontinuity in the temperature gradient, the cross-sectional area and the wetted perimeter of the gas passages by imposing continuity of mass and energy fluxes. Except for a special value of the temperature ratio of the two heat exchangers, the pressure fluctuates significantly around the initial value transiently, but it eventually tends to grow indefinitely or decay out. At a marginal case, it is observed that a traveling wave tends to emerge spontaneously. The traveling wave always propagates in the sense from the hot to cold heat exchangers in the tube outside of the stack. It is shown qualitatively that the traveling wave is enhanced as the porosity lowers.
Marginal conditions of thermoacoustic oscillations in a looped tube based on thick and thin diffusion-layer theories
Authors: Hyodo Hiroaki , Sugimoto Nobumasa
Published: May 2013

Marginal conditions for the onset of thermoacoustic oscillations of a gas in a looped tube with a “stack” inserted are examined by using two approximate equations for thick and thin thermoviscous diffusion layers in comparison with a span length of a gas passage. The equations are derived from the general thermoacoustic-wave equation valid for any thickness of the layer in the linear framework. Applying those approximate equations, respectively, to the gas in the stack and that in the outside of the stack, a frequency equation is derived by imposing matching conditions at both ends of the stack. Seeking a real solution for the frequency, the marginal conditions are obtained numerically for the temperature ratio at both ends of the stack. The ratio depends not only on the span length of one passage in the stack but also on its porosity. It is revealed that the temperature ratio decreases with increasing the span length and the porosity as well. This is the case when the thick diffusion layer is assumed in the stack. It is also revealed that a traveling wave tends to emerge in the tube outside of the stack in the sense from the hot end to cold end.
Introduction of conical phase adjuster for thermoacoustic system
Authors: Sakamoto Shin-ichi , Inoue Manabu , Nakano Yosuke , Orino Yuichiro , Inui Yoshitaka , Ikenoue Takumi , Wanatane Yoshiaki
Published: May 2013

We have proposed a phase adjuster for the thermoacoustic system and succeeded in improving the energy conversion efficiency from heat to the sound. A phase adjuster in a cylindrical shape was used in the past experiments. In this report, a conical phase adjuster is introduced. The inside diameter in one side of the phase adjuster is 20.5 mm, and the other is 39.5 mm. The length of phase adjuster is 45 mm.The phase adjuster is placed in two ways; the larger inner diameter of the phase adjuster is placed in the left side and the smaller is in the right (with PA L39.5 R20.5); the smaller inner diameter is in the left and the larger is in the right (with PA L20.5 R39.5).The total length of the loop is 3.3 m and the phase adjuster is placed 1.125 m away from the upper end of the prime mover stack in the clockwise direction. The measurements are conducted in three conditions: without phase adjuster and with each phase adjusters. Both the sound pressure and sound intensity generated in the thermoacoustic system with phase adjuster are greater than those without phase adjuster. The biggest sound intensity is observed with PA L39.5 R20.5.
Modeling disrupted tonotopicity of temporal coding following sensorineural hearing loss
Authors: Heinz Michael G. , Henry Kenneth S.
Published: May 2013

Perceptual studies suggest that sensorineural hearing loss (SNHL) affects neural coding of temporal fine structure (TFS) more than envelope (ENV). Although the “quantity” of TFS coding is degraded only in background noise, Wiener-kernel analyses suggest SNHL disrupts tonotopicity (i.e., the “quality”) of TFS coding for complex sounds more than ENV coding. Specifically, auditory-nerve (AN) fibers in noise-exposed chinchillas can have their dominant TFS component located within their tuning-curve tail (i.e., the wrong place) while their ENV response remains centered at CF. Here, the ability of a AN model [Zilany and Bruce (2007)] to replicate this dissociation between TFS and ENV tonotopicity was evaluated. By varying the degree of outer- and inner-hair-cell damage, hypothesized factors such as hypersensitive tails and tip-to-tail ratio were evaluated. The model predicted the main trends in our physiological data: (1) no loss of tonotopicity for lower CFs without a clear tip/tail distinction, (2) more easily disrupted TFS tonotopicity than ENV (without requiring hypersensitive tails), and (3) disruption of both TFS and ENV tonotopicity for severely degraded tips. This computational approach allows exploration of the interaction between tip-tail ratio and phase-locking roll-off, and whether amplification strategies can restore cochlear tonotopicity. [Work supported by NIH grants R01-DC009838 and F32-DC012236.]
Physiological prediction of masking release for normal-hearing and hearing-impaired listeners
Authors: Bruce Ian C. , Léger Agnès C. , Moore Brian C. , Lorenzi Christian
Published: May 2013

Léger et al. [J. Acoust. Soc. Am. (2012)] measured the intelligibility of speech in steady and spectrally or temporally modulated maskers for stimuli filtered into low- (<1.5 kHz) and mid-frequency (1–3 kHz) regions. Listeners with high-frequency hearing loss but near to clinically normal audiograms in the low- and mid-frequency regions showed poorer performance than a control group with normal hearing, but showed preserved spectral and temporal masking release. Here, we investigated whether a physiologically accurate model of the auditory periphery [Zilany et al., J. Acoust. Soc. Am. (2009)] can explain these masking release data. Intelligibility was predicted using the Neurogram SIMilarity (NSIM) metric of Hines and Harte [Speech Commun. (2010) and (2012)]. This metric can make use of either an “all-information” neurogram with small time bins or a “mean-rate” neurogram with large time bins. The average audiograms of the different groups of listeners from the study of Léger et al. were simulated in the model by applying different mixes of outer and/or inner hair cell impairment. Very accurate predictions of the human data for both normal-hearing and hearing-impaired groups were obtained from the all-information NSIM metric (i.e., taking into account phase-locking information) with threshold shifts produced predominantly by OHC impairment (and minimal IHC impairment).
Neural-scaled entropy as a model of information for speech perception
Authors: Alexander Joshua M. , Hariram Varsha
Published: May 2013

Neural-Scaled Entropy (NSE) is an objective metric used to quantify “information” available in speech consequent hearing loss, hearing aid signal processing, and distortion from various environmental factors. One pursuit is to use NSE to find optimum hearing aid settings that maximize speech perception. Inspired by the Cochlear-Scaled Entropy model [Stilp et al., J. Acoust. Soc. Am. 2112–2126 (2010)], NSE uses the neural spike output at the inner hair cell synapse of an auditory nerve model [Zilany et al., J. Acoust. Soc. Am. 126, 2390–2412 (2009)]. Probability of spike output from fibers sampled at equidistant places along the model cochlea is computed for short duration time frames. Potential information is estimated by using the Kullback-Liebler Divergence to describe how the pattern of neural firing at each frame differs from preceding frames in an auto-regressive manner. NSE was tested using nonsense syllables from various perceptual studies that included different signal processing schemes and was compared to performance for different vowel-defining parameters, consonant features, and talker gender. NSE has potential to serve as a model predictor of speech perception, and to capture the effects of sensorineural hearing loss beyond simple filter broadening. [Work supported by NIDCD RC1DC010601.]
Understanding hearing impairment through model predictions of brainstem responses
Authors: Verhulst Sarah , Bharadwaj Hari , Mehraei Golbarg , Shinn-Cunningham Barbara
Published: May 2013

Latencies of auditory brainstem response (ABR) wave-V decrease with increasing stimulus level, an effect often ascribed to broadened auditory filters. Following this hypothesis, hearing-impaired subjects with broad auditory filters should exhibit shorter wave-V latencies than normal-hearing listeners. Hearing anomalies resulting from the preferential degradation of low spontaneous rate (LS) auditory nerve (AN) fibers with intact thresholds have recently received attention. However, their effect on the ABR wave-V latency are yet to be elucidated. Here, a model of ABR investigates the relationships between wave-V latency and various forms of hearing damage. ABR wave-Vs are predicted from a model consisting of a nonlinear cochlear model (Verhulst et al., J. Acoust. Soc. Am. (in press)], an AN synapse model [Zilany et al., J. Acoust. Soc. Am. 126 (2009)], and a model of the cochlear nucleus (CN) and IC [Nelson and Carney, J. Acoust. Soc. Am. 116 (2004)]. Simulations predict that level changes cause smaller latency shifts in AN than in the IC, likely due to how inhibition/excitation shapes CN and IC responses. Furthermore, the increase in wave-V latency with decreasing click-to-noise ratios is predicted from LS fiber responses at low click-to-noise ratios. Preliminary simulation results suggest that wave-V latencies at different click-to-noise ratios may help diagnose LS damage.