bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound power level of speaking people
Authors: Caniato Marco , Bettarello Federica , Taffarel Michele
Published: May 2013

In restaurants and cafés many sound sources are present: music, refrigerant, and cooling equipment and people speaking. The smoking prohibition law did move out people creating a lot of aggregation areas outdoor, both in summer and in winter time. As a matter of facts many cafés open on the outer part a stallage in order to provide beverages to outside costumers. In this way, the “people speaking” source became a common problem to deal with and solve. In order to characterize this particular sound source in terms of sound power level of a typical stallage situation full of speaking people, sound pressure power measurements according to ISO 3446 standard were carried out. The results confirm the first investigation achievements provided by Sepulcri et al. with a non-direct method.
Waves of acoustically induced transparency in bubbly liquids: Theory and experiment
Authors: Gumerov Nail A. , Ohl Claus-Dieter , Akhatov Iskander S. , Sametov Sergei P. , Khazimullin Maksim V.
Published: May 2013

The theory of self-organization of bubbles in acoustic fields predicts formation and propagation of waves of self-induced acoustic transparency. This is a strongly nonlinear effect, which is a result of a two-way coupling of the sound field with the bubble distribution. We are challenging the theory with an experiment. Here, a homogeneous distribution of gas bubbles is first generated and then an ultrasonic field is switched on. The pressure waves are below the cavitation threshold and in a frequency range from 50 kHz to 200 kHz, mostly above the linear resonance frequency of the bubbles. The ultrasound leads to a rapidly propagating bubble wave away from the transducer. The dynamics is observed with a high-speed camera and analyzed. Interestingly, this transparent region is propagating through the bubbly liquid at velocities substantially higher than the bubble rise velocity due to the gravity. A simplified theoretical model of this acoustically induced transparency is developed. Both, analytical and numerical solutions are obtained. A comparison of the experimental data with the model is presented and the underlying physics of the problem is discussed.
Removal of living cells from biosensing surfaces in droplet-based microfluidics using surface acoustic waves
Authors: Bussonnière Adrien , Renaudin Alan , Miron Yannick , Grandbois Michel , Baudoin Michaël , Charette Paul
Published: May 2013

Removal of living biological cells from surfaces is a critical process for many applications in the area of biosensing and lab-on-a-chip. Trypsin is one of the most effective biochemical tools used to cleave the cells proteins that are responsible for bonding cells to surfaces [K. A. Walsh, Meth. Enzymol. 19, 41 (1970)]. We propose a method using Rayleigh-type (20 MHz) surface acoustic wave (SAW)-based mixing [Renaudin et al., Lab Chip 10, 111 (2010)] as an accelerator for trypsin-mediated removal of living cells from surfaces. In the experiments, a 10 μL droplet of Hank’s Balanced Salt Solution (HBSS)-trypsin is placed on a piezoelectric substrate covered with human embryonic kidney cells (HEK293). Using phase contrast microscopy, cells removal time for different acoustic power levels and trypsin concentrations is measured. Results from validation experiments show that a minimum of 180 s is necessary to completely release surface-bonded cells covered by the 10 µL droplet without the use of SAW (negative control). By using microstreaming flow in the droplets generated by the SAW, cells are released from the surface in less than 8 s. This work will contribute to improved lab-on-a-chip devices based on living cell biosensing.
Conventional and spatial principal component analysis on near-field head-related transfer functions
Authors: Xie Bo-sun , Zhang Cheng-yun
Published: May 2013

Head-related transfer functions (HRTFs) vary with both frequency and source position. The near-field HRTFs with source distance less than 1.0 m are particularly complicated due to their distance dependence. Principal component analysis (PCA), which is conventionally carried out in the frequency or time domain, has been widely applied to reduce the dimensionality of far-field HRTF data with source distance greater than 1.0 m. The present work first extends the conventional PCA, and then proposes a spatial PCA method in the spatial domain rather than in the frequency or time domain to reduce the dimensionality of near-field HRTF data. An illustrative case indicates that near-field HRTF magnitudes at 9 distances with 493 directions for each distance can be approximately represented by the weighted sum of 15 spectral shape basis functions using the conventional PCA or the weighted sum of 15 spatial basis functions using the spatial PCA. Both representations account for more than 98% energy variation of the original data, and reduce the dimensionality of the original data to about a quarter. The proposed method is also applicable to the head-related impulse responses in the time domain. Furthermore, the spatial PCA scheme is potentially applicable to simplify near-field HRTF measurement.
Calculation of listener-specific head-related transfer functions: Effect of mesh quality
Authors: Ziegelwanger Harald , Majdak Piotr , Reichinger Andreas
Published: May 2013

The geometry of head and ears defines the listener-specific directional filtering of the incoming sound. The filtering is represented by the head-related transfer functions (HRTFs), which provide spectral features relevant for the localization of sound-sources. HRTFs can be acoustically measured or numerically calculated based on a geometric representation of the listener. While the acoustically measured HRTFs usually provide localization performance similar to that obtained in free-field listening, the performance obtained with numerically simulated HRTFs, however, heavily depends on the quality of the geometric and acoustic model of the listener used for the simulation. In this study, we show how to calculate listener-specific HRTFs with spectral features similar to that from acoustically measured HRTFs for the entire audible frequency range. We review the boundary-element method coupled with the fast-multipole method and we present details on the prerequisites like the geometry-capture technique, acoustical parameters, and the numerical algorithms. Further, the effect of the mesh quality on the HRTFs was investigated by systematically varying the average edge length from 1 to 5 mm. The HRTF amplitude spectra were analyzed and evaluated by visual comparison and in a localization model. The optimal average edge length for a fast calculation of HRTFs yielding potentially good localization performance is discussed.
Spectral uncertainty and similarity effects in informational masking identically related to the Simpson-Fitter metric of target-masker separation
Authors: Chang An-Chieh , Stamas Jacob , Heo Inseok , Gilbertson Lynn , Lutfi Robert
Published: May 2013

Evidence is provided suggesting a primary dependence of informational masking (IM) on the stochastic separation of target and masker given by Simpson-Fitter’s da [Lutfi et al. J. Acoust. Soc. Am. 132, EL109-113 (2012)]. The stimuli were synthesized impact sounds of plates played in sequence as masker-target-masker triads. Their spectra varied independently and at random on each presentation as would correspond to changes in plate size. In the 2IFC procedure the listener’s task was to choose the larger-sized target. The effect of spectral uncertainty regarding the masker was examined by measuring d’ performance for different values of the variance in masker size. The effect of spectral similarity of target and masker was examined by measuring performance for different values of the mean difference between target and masker size. The functions relating d’ to da in both cases were identical and of similar slope across listeners. Identical functions were also obtained, though with shallower slopes, when listeners judged the target hit with greater impact force. The results are considered in terms of their implications for the development of a model of IM that emphasizes the statistical properties of signals over loosely defined concepts of target-masker similarity and masker uncertainty.
Boundary effects on the illusory continuity of and interrupted glide through a notched noise
Authors: Ciocca Valter , Haywood Nicholas
Published: May 2013

This study investigated the illusory continuity of an interrupted frequency glide through a notched-noise burst. A 2I-2AFC procedure was used to measure detection of the (target) portion of the frequency glide that overlapped in time with the noise. The portions of the glide preceding and following the noise (flankers) could be present or absent. The center frequency of the notch coincided with either the frequency end-point of the flanker that preceded the noise, or the onset frequency of the flanker that followed the noise. A control condition with a wide-band noise burst (absent notch) was also included. Performance was poorest in the absent notch condition and was significantly poorer with present than with absent flankers. This suggests that listeners perceptually restored the missing target when flankers were present. Performance was also less accurate (indicating stronger illusory continuity) when the notch was centered on the end-point of the flanker that preceded the noise. These results suggest that the masking of the onset of the flanker following the noise provides a stronger cue to the perception of continuity than the masking of the offset of the flanker that precedes the noise.
Improving the sound absorbing efficiency of closed-cell foams using shock waves
Authors: Doutres Olivier , Atalla Noureddine , Brouillette Martin , Hébert Christian , Begg David
Published: May 2013

Producing closed-cell foams is generally cheaper and simpler than open-cell foams. However, the acoustic efficiency of closed-cell foam materials is poor because it is very difficult for the acoustic waves to penetrate the material. A method to remove the membranes closing the cell pores (known as reticulations) and thus to improve the acoustic behavior of closed-cell foam material is presented. The method is based on the propagation of shock waves inside the foam aggregate where both the shock wave generator and the foam are in air at room conditions. Various shock treatments have been carried out on a polyurethane foams, and the following conclusions were drawn: (1) the reticulation rate increases and thus the airflow resistivity decreases while increasing the amplitude of the shock treatment; (2) the softness of the foam increases; (3) the process is reliable and repeatable; (4) obtained acoustic performance is comparable to classical thermal reticulation; and (5) the process can be used to control the reticulation rate along the thickness.
Omnidirectional acoustic absorber with a porous core—Theory and measurements
Authors: Umnova Olga , Elliott Andy , Venegas Rodolfo
Published: May 2013

An omni-directional acoustic absorber consisting of a porous core and the impedance matching metamaterial layer has been designed and tested in the laboratory. Semi-analytical and numerical models have been developed and validated. The numerical model takes into account the viscous losses in the matching layer. A 1.5 m demonstrator has been built and tested under acoustic and weak shock excitation. Testing with acoustic excitation showed good agreement between measurement and model, with near perfect absorption between 400 and 1000 Hz. Testing against weak single-pulse shock in an anechoic chamber also confirmed a significant reduction in peak pressure levels when compared to a conventional porous absorber without matching layer. The findings suggest that structure is equally effective when wrapped around an object like a column, pipeline, or the underside of a vehicle, as it would be when entirely filled with an absorbing porous material.
The use of mixed effects models in quantifying the dynamics of speech
Authors: Iskarous Khalil
Published: May 2013

Mixed-effects models have been used often in quantifying the variability in data from experiments in speech and language. In most of these experiments, the dependent variable is measured at some landmark of a kinematic or decision process. However mixed-effects models are increasingly being used to quantify the variability of dependent variables that vary in time, such as articulator movements, formant transitions, and eye tracking data. This presentation will first provide a tutorial introduction to the use of the mixed-effects model, especially the growth-curve variant, for quantifying variability where time is an essential independent variable. It will then be argued that the model coefficients can be interpreted as dynamic coefficients of differential equations that describe the dynamics of the underlying processes.
Investigation of calculation methods of effective duration on autocorrelation-based Chinese speech recognition
Authors: Huang Kun Peng , Ando Yoichi
Published: May 2013

The factors extracted from running autocorrelation function have phonetic and syllabic meanings, and they can be used for Chinese speech recognition. One of the factors is the effective duration of ACF envelope τe, which reveals the temporal repetitive continuity of the speech signals. The values of τe vary when different calculation methods are adopted. By adopting different calculation methods to several sets of Chinese vowels and characters, which are recorded from a group of speakers, a preferred calculation method is decided by the uniqueness of τe, that is the τe calculated by such method can mostly distinguish different vowels, characters, or even speakers.
Quasi-holographic processing as an alternative to synthetic aperture sonar imaging
Authors: Zartman David J. , Plotnick Daniel S. , Marston Timothy M. , Marston Philip L.
Published: May 2013

By limiting attention to supersonic-like wavevectors, time-resolved holographic imaging was demonstrated to be helpful for identifying transient elastic responses of targets contributing to far field scattering [Hefner and Marston, Acoust. Res. Lett. Online 2, 55–60 (2001); 3, 101–106 (2002)]. That approach was applied to time-evolving three-dimensional wavefields scanned with a two-dimensional raster scan at a significant offset. In recent work, however, it was also demonstrated that line scan measurements of bistatic scattering could be processed quasi-holographically as an alternative to synthetic aperture sonar (SAS) imaging [Baik et al., J. Acoust. Soc. Am. 130, 3838–3851 (2011)]. The present investigation broadens the line scan approach to reversible signal extraction associated with image features, and to monostatic quasi-holographic imaging, in which the source and receiver are co-located and scanned along a line. Some applications of this approach will be illustrated such as separation of signals from edge diffraction features and specular features from those of elastic features. [Work supported by ONR and the NSWC-PCD ILIR/IAR research fund.]
Modified statistically optimized near-field acoustical holography for jet noise characterization
Authors: Wall Alan T. , Gee Kent L. , Neilsen Tracianne B.
Published: May 2013

Near-field acoustical holography has been shown to be a useful tool for visualizing jet noise fields. It has been applied to a full-scale jet on an installed military aircraft with promising results, but the source characteristics in the extreme near field have been difficult to characterize because of the interference of acoustic reflections off the rigid reflecting plane beneath the jet. To provide accurate sound field reconstructions, a modified approach to statistically optimized near-field acoustical holography (SONAH) is implemented. In conventional SONAH, the sound field is represented by a matrix of elementary wave functions at all desired spatial locations. In this modified approach, advantage is taken of the property that arbitrary, user-defined functions can be selected for this matrix. Here, two sets of cylindrical wave functions, one centered on the jet centerline and one on the image source centerline, are used to obtain an accurate near-field reconstruction.
A study on the effect of sound velocity estimation for underground imaging
Authors: Toh Ryo , Sakuma Takuya , Motooka Seiichi
Published: May 2013

An efficient technique for detecting objects buried underground is expected for archaeological exploration and civil engineering. We have proposed a three dimensional underground imaging method by using an amplitude correlation synthesis processing and an electromagnetic induction type sound source. Because the sound velocity of sand and soil depends on a lot of physical parameters that varies with the area, it is needed to be measured before imaging processing. Up to now, the sound velocity employed for signal processing is measured by receivers buried underground near the area to be detected. In order to improve the efficiency of field detection, a method of estimating the underground sound velocity by the sound velocity measured from the ground surface is studied. In this study, the comparison experimental results of the velocity of underground transverse wave, the velocity of underground longitudinal wave, and the sound velocity measured from the ground surface are introduced. Furthermore, the effect on the image of underground objects brought forth by the sound velocity estimation is discussed.
Abnormal events recognition and classification for pipeline monitoring systems based on vibration analysis and artificial neural networks
Authors: Chen Bin , Cheng Xiaobin
Published: May 2013

Pipelines have become the principal means of oil and gas transportation. However, pipeline leakage takes place due to some natural or artificial damages, which may cause loss of life and properties along with the environmental pollutions. A new pipeline detection and pre-warning system based on distributed optical fiber sensor is proposed, and the hardware has been accomplished. Now, its following key problem is how to recognize and classify the abnormal events, such as oil stealing, construction, artificial excavation, motor work, and train passing. This paper involves a study on this and proposes a solution method. First, original vibration signal is pre-processed and segmented according to threshold of energy within a narrower bandwidth. Then, event features in time and frequency domain are analyzed through statistical analysis and short-time Fourier transform (STFT). The energy coefficients at some bandwidth can distinguish different type of abnormal events, which are chosen as feature vectors. At classification, abnormal events are first divided into discrete and continuous events with single classifier, which can decrease classified event sets and improve recognition accuracy. Then, BP artificial neural network is applied to identify the type of abnormal events. Finally, proposed method will be verified with actual collection data sets.
Objective analysis of higher-order ambisonics sound-field reproduction for hearing aid applications
Authors: Orinos Chris , Buchholz Jorg M.
Published: May 2013

The evaluation of hearing aids (HAs) inside realistic sound environments is of increasing interest. Higher-order Ambisonics (HOA) has been used for loudspeaker-based sound field resynthesis and HOA recording microphone arrays are available. Although HOA has been evaluated perceptually, it is unclear how far the results can be transferred to evaluating HA technologies (particularly multi-microphone enhancement algorithms). In order to determine the minimum HOA order required for HA testing, an HOA framework was developed, simulating the entire path from sound presented in a room, picked up by a microphone array, decoded, and received at the ears of a HA-fitted dummy head. HA directivity patterns were compared between an ideal free-field and its HOA representation to evaluate the introduced error. In-room analysis was conducted to investigate the bandwidth and performance of a directional microphone in realistic situations. For a bandwidth B, the required order Mmin was found to be Mmin ≥ B/600 Hz for the anechoic (worst) case scenario. The presence of reverberation introduced natural room response variations across different source-receiver locations, suggesting that the acceptable HOA error can be increased. Hence, in reverberant environments, the required HOA order is reduced, and at least 2D HOA reproduction can be used for evaluation of HA technologies.
Steerable parametric loudspeaker with preprocessing methods
Authors: Shi Chuang , Gan Woon-Seng
Published: May 2013

The emerging applications of the parametric loudspeaker, such as 3D audio, require both directivity control and high fidelity at the audible frequency (i.e., the difference frequency of the primary frequencies generated by the parametric loudspeaker). Although the phased array techniques have been applied and proved adequate to adjust the steering angles of the parametric loudspeaker, and preprocessing methods have been studied to reduce the harmonic distortions, there is no published work on the effectiveness of the combination of the beamsteering method and the preprocessing methods for the broadband steerable sound beam system. This paper aims to investigate on this unexplored problem. First, the relation between the phases of the primary waves and the difference frequency wave is explored to prove the feasibility of achieving a broadband steerable sound beam from the parametric loudspeaker with preprocessing methods. Second, based on the derived relation, the beamsteering structure is proposed. Lastly, preprocessing methods are proposed for the steerable parametric loudspeaker using double sideband modulation (DSBAM) and square root amplitude modulation (SRAM) methods. Spatial performances of the steerable parametric loudspeaker with preprocessing methods are presented in this paper.
Evaluation of different spatial windows for a multi-channel audio interpolation system
Authors: Trevino Lopez Jorge A. , Okamoto Takuma , Iwaya Yukio , Suzuki Yôiti
Published: May 2013

The adoption rate of multi-channel audio systems has dramatically increased in recent years. It is common to find 5.1- or 7.1-channel systems in typical home theaters. However, most users do not setup the satellite loudspeakers at the prescribed positions for aesthetic reasons or due to space constraints. Recently, we introduced a technique to optimize multi-channel contents for reproduction over non-ideal loudspeaker setups. Our proposal improves localization accuracy for sound sources reproduced by horizontal loudspeaker arrays. It can also be extended to handle full 3D contents, like those of the upcoming 22.2-channel standard. The proposed method works by applying a set of spatial windows centered at the loudspeaker positions and interpolating along the angles using the spherical harmonics. We now extend our previous results by evaluating the performance of six different spatial window functions. We consider the 5-channel distribution of ITU recommendation BS.775-2, as well as four variations that end-users are likely to deploy. Apparent sound source locations are estimated from the energy and velocity vectors at the sweet spot. Our study found that using the Slepian window with our proposal and a non-ideal loudspeaker layout leads to a reproduced sound field that is closer to that of the ideal configuration.
In situ calibration of seafloor acoustic backscatter data from swath mapping sonars
Authors: de Moustier Christian , Kraft Barbara J.
Published: May 2013

Geometric and radiometric corrections are necessary to convert raw seafloor acoustic backscatter data to imagery in which the intensity variations are due to the geoacoustical properties of the bottom and the angular dependence of the backscattering process. Radiometric corrections include removal of the combined effects of the sonar's transmit and receive beam patterns, and removal of the area ensonified. To this end, a method is presented to estimate the transmit/receive beam pattern of a multibeam swath mapping sonar using seafloor acoustic backscatter data collected over an entire survey area. This involves estimating the scattering area at each sounding based on local seafloor slopes. For a given sonar installation, results show that such beam pattern estimates remain stable to within ± 0.5 dB over different survey areas.
Inversion of seabed acoustic parameters in shallow water using the warping transform
Authors: Zeng Juan , Chapman N.Ross , Ma Li , Chen Yan
Published: May 2013

In this paper, a method is described for inverting geoacoustic parameters of the seabed from short range field data recorded by single hydrophone. The original data in time domain are processed by a warping operator at first, and then, the dispersion curve and the mode amplitude ratios are extracted separately from the warped data. The velocity and the density in the bottom are inverted from the dispersion curve, and the attenuation from the mode amplitude ratios, respectively. The performance of the method is examined using simulated data and then experimental data from the North Sea of China. The source used in the experiment was a small explosive charge that provided good signal to noise ratio over the frequency band from 200 Hz to 1 kHz. The depth of the water was about 30 m, and the water sound speed was nearly constant with depth. The seabed geoacoustic parameters are inverted from the data received at different ranges from 2 to 14 km. The results from the different ranges are consistent with a simple half space model of the bottom. The seabed velocity is about 1600 m/s.
Electrochemical basis of the card-house model of mud and its acoustical implications
Authors: Fayton Joseph O. , Pierce Allan D. , Siegmann William L.
Published: May 2013

A basic mud model contains thin mineral (kaolinite and smectite) particles, roughly hexagonally shaped platelets, with diameters typically 1 micron. Isomorphous substitution causes each platelet to carry a net negative charge per unit area. Because the ions in the surrounding water respond so that there is a net positive charge on both sides of the platelet, each platelet is modeled as a sheet of longitudinal electric quadrupoles aligned perpendicular to the surface. The electrical interaction between platelets is responsible for the card-house structure, whereby the edge of one platelet touches a central line along the surface of another platelet, with the platelets being at right angles to each other. When the perpendicular arrangement is perturbed, a restoring torque attempts to return the platelets to their original state. Electrostatic analysis is used to explain why the restoring torque is formally singular at the joining line when one platelet is slightly tilted from perpendicular. The singular behavior appears to arise when the corners of one platelet touch the edge of another. This singularity requires imposition of the cantilever boundary condition in order to consider the shear resistance of mud, with each platelet bending as an elastic plate. [Research supported by SMART Fellowship and ONR.]
Electric guitar—A blank canvas for timbre and tone
Authors: Case Alex , Roginska Agnieszka , Matthew Justin , Anderson Jim
Published: May 2013

The electric guitar is a complex mechanical, electrical, and acoustic system, invented less than a century ago. While more traditional instruments such as voices and violins, trumpets and tympani, piano and piccolo might possess innate traits that most listeners easily identify, the electric guitar is a sound synthesizer capable of a vast range of sounds. The guitar, the amp, and the recording techniques used enable the performer and the engineer to define and refine elements of tone, almost without limit. Electric guitar has no single reference tone quality, but instead invites, and even inspires performers and recordists to create new sounds and explore alternative timbres as desired.
Increased scattering efficiency through cell optimization in acoustic diffusers
Authors: Lenz Richard L.
Published: May 2013

This presentation will provide test data, experiments, and analysis in showing the interaction of absorption and diffusion characteristics. It will be shown that absorption, either additive or design inherent, has an adverse effect on the efficiency of the acoustic diffusers. The effects of low frequency interference on various cell structures of quadratic residue diffusers will be highlighted as a prime example of this theory. The inclusion of additive absorption, i.e., fabric, fiberglass, and other materials, further complicates the matter of diffuser efficiency. While design characteristics of some diffusers, such as prime root and quadratic residue diffusers, can be used effectively for their absorption coefficients, overall these characteristics detract from the efficiency of the diffusion coefficients. Product designs utilizing optimized cell designs to inhibit absorption in diffusers will be shown. It will be shown that this cell optimization dramatically increases the efficiency of the diffuser. This optimization includes both higher scattering coefficients and smoother frequency responses. Comparative analysis will be provided with traditional designs and newer optimized designs.
From felt to fungus: New materials and applications—Focus on innovation and exploration
Authors: Schuette Dawn , Pfeiffer Scott
Published: May 2013

A two-part presentation of new materials for use in architectural acoustics. This presentation emphasizes new materials, both commercially available and those pressed into use for acoustic benefit. The companion session is presented in “Cultivating the Sustainable in Architectural Acoustics.” Contemporary architectural design often seeks to push the standard of construction, resulting in the need to explore new acoustic solutions to new architectural challenges. Innovative use of commercially available materials or exploration into the development of new materials or modifications of known materials is required to find the best solutions both acoustically and architecturally. Use of acoustical products and non-acoustical products for acoustical benefit are reviewed through case studies.
Sound absorption and transmission through flexible micro-perforated structures
Authors: Maury Cédric , Bravo Teresa , Pinhède Cédric
Published: May 2013

This work presents a theoretical and experimental study on sound absorption and transmission through structures made up of single and multiple-layer micro-perforated panels (MPPs). As they contribute to improve acoustical comfort, speech intelligibility and comply with lightweight, transparency and fiberless requirements, increasing applications are found in architectural acoustics or in the aeronautic and surface transport industries. A fully coupled modal approach is proposed to calculate the absorption coefficient and the transmission loss of finite-sized layouts made up of multiple flexible MPPs separated by air gaps. Validation results are obtained for single and double-layer thin MPPs against the transfer matrix approach and against measurements performed in a standing wave tube and in an anechoic chamber. Analytical approximations are derived from coupled-mode analysis for the Helmholtz-type and structural resonance frequencies of a single layer MPP structure together with relationships on the air-frame relative velocity over the MPP surface at these resonances. Principled guidelines are provided for enhancing both the sound absorption and transmission properties of multiple-layer MPP structures through suitable setting of the design parameters.
A supervised approach for segmentation of bioacoustics audio recordings
Authors: Briggs Forrest , Raich Raviv , Fern Xiaoli
Published: May 2013

Segmentation is one of the most important tasks in preprocessing audio recordings for species recognition. For examples, bird songs or calls often consist of distinct short utterances. Correctly segmenting such utterances is an essential step in the analysis of bird songs or calls. Energy based time-domain segmentation is commonly used and can be fairly effective when dealing with high signal-to-noise ratio recordings of a single individual. We consider the scenario in which omnidirectional microphone are deployed for round-the-clock in-situ species monitoring. In such scenario, recordings may suffer from two problems: (i) low signal-to-noise ratio and (ii) simultaneous vocalizations of multiple individuals. We are interested in segmentation of such recordings. We propose a framework for supervised time-frequency segmentation of audio recordings. Using manually labeled spectrograms, a classifier is trained to separate vocalization from the background noise in the two dimensional time-frequency domain.
Conditioning for marine bioacoustic signal detection and classification
Authors: Mellinger David K.
Published: May 2013

Marine acoustic signals are characterized by certain types of noise and interference. Conditioning methods applied to spectrograms can be used to reduce or even remove these sounds, making bioacoustic signals more evident and simplifying the tasks of detection and classification. One family of methods is for making a long-term estimate of noise at each frequency and subtracting this estimate from the spectrogram; this has the beneficial effects of whitening the noise spectrum and removing relatively stationary noise sources such as vessel sound, but has the detrimental effect that relative spectrum levels—important in echolocation click classification—are altered. Another method estimates the spectrum in narrow bands at each time step and subtracts this estimate from the corresponding spectrogram frame; this method is useful for tonal sound detection and classification in that it removes short-duration clicks from snapping shrimp and echolocating animals. Other methods for removing other, more rare types of noise are presented as well. Examples and performance characterization of these methods are presented. [Funding from ONR and N45.]
Inversion of density in the ocean from seismic reflection data
Authors: Biescas Gorriz Berta , Ruddick Barry , Sallares Valenti
Published: May 2013

Vertical stability of the fluid particles, mixing, and mesoscale motions in the ocean interior occur mostly along-isopycnals surfaces. Therefore, potential density profiles with high lateral resolution would provide important information about the fluid dynamic and the general circulation in the ocean. Could we observe density changes from seismic data? Is seismic oceanography able to measure density with enough accuracy? How is the relation between seismic reflectors and isopycnals surfaces? We have inverted oceanic impedance from seismic data and then derived density and potential density surfaces from the oceanic impedance. Results of the inverted potential density have been compared with digitized seismic reflectors to show the relation between isopycnals and reflectors. We have also compare the seismic profiles of the GO Survey with the space-coincident CTDs and space and time-coincident XBTs to understand the nature of the reflectivity and its relation with the physical parameters of the ocean.
A biologically inspired silicon differential microphone with active Q control and optical sensing
Authors: Miles Ronald , Degertekin Levent , Cui Weili , Su Quang , Homentcovschi Dorel , Fredrick Banser
Published: May 2013

A MEMS differential microphone is described in which the diaphragm design is inspired by the mechanics of directional hearing in the fly Ormia ochracea. The 1 mm by 3 mm diaphragm is designed to rotate about a central pivot in response to sound pressure gradients. The diaphragm is designed to have its dominant resonance mode within the audible frequency range and to have as little viscous damping as possible (to minimize the effects of thermal noise). The motion of the diaphragm is detected using an optical sensing scheme that includes a semiconductor laser (VCSEL), photodetectors, a mirror, and a diffraction grating. To minimize the adverse effects of the light damping on the response, an active feedback system is implemented to achieve active Q control. This uses the output of the optical detection scheme to drive the diaphragm through a capacitive actuator. The microphone and optoelectronics are packaged into an assembly that can be incorporated into a mock behind-the-ear hearing aid. The microphone is shown to achieve a noise floor that is approximately 17 dBA lower than what can be achieved using a pair of existing low noise hearing aid microphones to create a directional hearing aid.
Biomimetic flow sensors for environmental awareness
Authors: Krijnen Gijs , Droogendijk Harmen , Casas Jerome , Dagamseh Ahmad
Published: May 2013

Crickets possess hairy organs attached to their abdomen, the so-called cerci. These cerci contain highly flow-sensitive mechanosensors that enable the crickets to monitor the flow-field around them and react to specific stimuli form the environment, e.g., air-movements generated by hunting spiders. Salient is the sensitivity of these sensors, which work at thermal noise threshold levels, and the large number of hairs which, together with the necessary neural processing, allows the cricket to use the cerci as a kind of “flow-camera.” Biologists and engineers have been working together in the recent past to regenerate part of the outstanding sensing capabilities of crickets in manmade, bio-inspired flow-sensor arrays. Using micro-electromechanical systems (MEMS) technology, sensors are created that are sensitive and show a high degree of directivity. By analyzing the governing physics, the sensors have been optimized to the point that currently the electronic interfacing is the limiting factor. Nonlinear parametric effects are used to increase the range of applicability of the sensors. Stochastic resonance is investigated to further enhance sensing capabilities. Arrays of sensors, interfaced using frequency division multiplexing (FDM), have been demonstrated to enable the tracking of the movement of small spheres.
A novel two dimensional particle velocity sensor
Authors: Pjetri Olti , Wiegerink Remco J. , Lammerink Theo S. , Krijnen Gijs J.
Published: May 2013

In this paper, we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0 × 2.5 × 0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabricate. The sensor consists of two crossed beams of SiRN with a platinum layer on top. These beams are used both as heaters and sensors. Two currents with equal amplitude are injected in both terminals of one of the beams and are extracted from the terminals of the other beam. A particle velocity component in the direction of a beam will cause its temperature, and thus resistance, profile to change asymmetrically. This asymmetry in resistance will give rise to a voltage difference across that beam which is proportional to the particle velocity level. The sensor shows a frequency bandwidth between 20 Hz and 10 kHz.The two figures of eight are exactly perpendicular to each other as desired, which was difficult to obtain in earlier implementations using parallel beams. Furthermore, the structure consisting of two crossed wires increases the mechanical robustness of the beams resulting in fabrication yields of 94% as opposed to 70% in earlier implementations.
Calibration of smartphone-based devices for noise exposure monitoring: Method, implementation, and uncertainties of measurement
Authors: Dumoulin Romain , Voix Jeremie
Published: May 2013

Standardized noise exposure campaigns have as their principle disadvantages the cost of instrumentation and the difficulties associated with practical deployment in the field. Our ongoing research evaluates the suitability of an alternate solution based on smartphone sensing: the occupational noise exposure and its associated measurement uncertainties are estimated from a spatio-temporal analysis of smartphones noise measurements and GPS data. This paper presents a diffuse field calibration method for such smartphone-based devices. The measurements methods and the calculation of expanded uncertainties for a large range of sound levels are detailed. The calibration corrections include a frequency response linearization and an A-weighted sound level correction, which is function of the C-A spectral balance of the sound pressure levels measured. To later ensure a realistic correction, these spectral balance values come from distribution of referenced industrial noise databases. An Android™ “app” has also been developed to measure the noise levels and to compute the calibration and corrections factors. Finally, an laboratory validation is conducted to evaluate, on a population of calibrated smartphone-based devices, the measurement errors associated with such devices as a function of microphone directivity, linearity, and frequency response.
Using your ears: A novel way to teach acoustics
Authors: Ronsse Lauren , Chéenne Dominique J. , Kaddatz Sarah
Published: May 2013

Auditory simulations of physical phenomena pertaining to acoustics have been developed to enhance student learning and understanding of these conditions. The demonstrations range from simulations of fundamental concepts, such as reverberation, flutter echoes, reflections, and room modal effects, to more applied topics, such as sound transmission through barriers, mechanical system noise spectra, and varying absorption distribution in rooms. The simulations were generated by using auralization tools and processed recordings. The demonstrations may be utilized in the classroom to introduce new acoustical concepts by having students first listen to a simulation, then write and/or discuss what they hear, providing conjectures about the parameters that could create such acoustical conditions. The goal of the demonstrations is to encourage students to use their ears as part of a quantitative and qualitative assessments of acoustical phenomena.
Aeroacoustics of the panpipes
Authors: Auvray Roman , Fabre Benoı̂t , Meneses Felipe , de la Cuadra Patricio , Lagrée Pierre-Yves
Published: May 2013

The generic term “flute-like instruments” includes a wide variety of instruments whose sound production is ensured by the coupling of an air jet with an acoustic resonator. Within the family, different kinds of resonator (for instance Helmholtz resonator, open-open, or open-closed tube), may be used with different kind of air supply systems such as the ones found in the recorder, the flue organ pipe, or the shakuhachi. It is common to extent the results obtained on one of the member of the family to the whole family. However, when an accurate description of the sound production mechanisms is required, small discrepancies may arise due to the wide variability in the geometries or in the air supply systems. Among other, a closed-end flute may have a different behavior than an open-open flute since the recirculation of air flow within the pipe may alter the hydrodynamics of the jet, and thus the auto-oscillation process. While most of the studies on flute-like instruments have focused on open pipes (organ pipes and recorder), the panpipes (a representative closed-end flute) has only received little attention. We present experimental data, including flow visualization and pressure signal measurement gathered on a closed pipe. A model of the flow in the pipe allows to interpret the data and compare the behavior of a closed pipe blown with a turbulent jet with that of an open pipe blown with a laminar jet.
Aerodynamical sounding mechanism in flue instruments: Acceleration unbalance between the jet vortex layers
Authors: Yoshikawa Shigeru
Published: May 2013

According to particle image velocimetry (PIV) measurement applied to the sound production in organ flue pipes and flutes, the vortex shedding at the pipe edge proposed by Howe (1975) are not observed but the formation of the vortex layer is clearly observed along both sides of the jet flow. This has been confirmed in various sounding conditions with different blowing pressures and resulting pitches. The acceleration unbalance is generated from an incomplete cancelation of the aeroacoustical source term (ω×U) between both sides of the jet, where U is the jet velocity and ω (= rotU) the vorticity. In addition, the vortex layer is essentially unstable because it is formed along the inflection point of the lateral jet-velocity profile. Therefore, the acceleration unbalance and inflection instability of the vortex layer activates the jet wavy motion to reinforce the inward or outward acoustic velocity u at the pipe mouth. Phase relations between acoustic quantities approve conventional acoustical models based on the volume-flow drive and momentum drive. Since ω×U can also activate the jet movement in edge-tone generation, the vortex-layer formation may be regarded as the fluid-dynamical mechanism common to the edge-tone generation and the pipe-tone generation.
Numerical analysis of the interaction between fluid flow and acoustic field at the mouth-opening of a flue instrument
Authors: Akamura Takahiro , Nagao Yuki , Iwasaki Takuya , Nakano Ken'ichiro , Takahashi Kin'ya , Kobayashi Taizo , Takami Toshimi , Nishida Akira , Aoyagi Mutsumi
Published: May 2013

The fluid-sound interaction is the key to understanding the sounding mechanism of flue instruments. The formula introduced by Howe allows us to estimate the energy transfer between acoustic field and hydro-dynamic field. For calculation of Howe’s formula, it is necessary to divide acoustic fields from fluid, but we do not have any established method to do it, yet. Recently, several authors developed approximate methods to evaluate Howe’s formula and applied to experiments of cavity noise, flue instruments and so on. In this talk, we introduce a numerical method to calculate Howe’s formula, which is similar to those above. Our model is a small flue-organ like instrument with an end-stop. We use compressible large-eddy simulation (LES), which is able to reproduce the fluid flow and acoustic field, simultaneously. First, fluid flow and acoustic oscillation excited in the pipe by a jet-injection from the flue are reproduced by LES. Next, an acoustic field is reproduced by LES without the jet-injection but with driving at the far end, pressure driving, particle velocity driving or oscillating wall driving (like a loudspeaker). Combining those results allows us to calculate Howe’s formula and to estimate the fluid-sound interactions.
Detectability study of warning signals in urban background noises: A first step for designing the sound of electric vehicles
Authors: Misdariis Nicolas , Gruson Anais , Susini Patrick
Published: May 2013

Electric vehicles tend to become a growing category of today’s human means of transport. But, because these kind of vehicles are actually quiet, or even silent, the question of a dedicated sound design arises almost inevitably in order to make them more present—then secure—both for their proximity (pedestrians) and their users (driver). This being, current issues for a sound design research framework is then to exploit and explore sound properties that, first, will fix a goal of functionality (emergence, recognition, acceptance) and, second, will define guidelines for the development of new aesthetics to be included in a general design approach. Thus, a first study focusing on detection of warning signals in urban environments was achieved. Based on the state-of-the-art, a corpus of elementary signals was built and characterized in a time/frequency domain for representing basic temporal and spectral properties (continuous, impulsive, harmonic, etc.). A corpus of representative urban environments was also recorded and realistic sequences were mixed with a dynamic approaching-source model. A reaction time experiment was conducted and leads to interesting observations: especially, specific properties promoting the emergence. Moreover, a seemingly significant learning effect also rises from the data and should be further investigated.