bluuebunny/crossref_metadata_2025 huggingface dataset:
Platform for virtual auditory environment real time rendering system
Authors: Zhang Chengyun , Xie Bosun
Published: April 2012

By dynamically synthesizing binaural signals in free-field and reflective environment, a virtual auditory environment (VAE) real time rendering system recreates realistic auditory events or perceptions for listeners. VAE systems have been applied in various fields, such as the research of binaural hearing, multimedia and virtual reality, among others. In present work, a PC and C++ language-based VAE system is designed and implemented. Schemes for improving the performances of the system, including multiple virtual source synthesis, auditory distance perception, dynamic information simulation for multiple degrees of freedom of listener, as well as dynamic characters of the system, are proposed. The results from measurement indicate that the system is capable of synthesizing 280 virtual sound sources (including free-field sources and image sources for reflections) simultaneously in conventional working mode, or 4500 virtual sources in proposed PCA (principal components analysis) working mode. The update rate is 120 Hz, and the system latency is 25.4ms. A set of psychoacoustic experiments also validate the performance of the system. The function extension of VAE can serve as a flexible and powerful platform for binaural and virtual reality research.
The use of relative weights to assess perceptual segregation in a concurrent profile analysis task
Authors: Shen Yi
Published: April 2012

A series of experiments were conducted to address the need of a psychophysical tool to measure the perceptual segregation of concurrent sources. The experiments measured listeners' sensitivity to the spectral profile of a target sound embedded in a concurrent masker. Both the target and masker were harmonic complexes, which were presented at different fundamental frequencies in order to investigate the effects of this acoustic cue on segregation. The task was designed so that it either strongly encouraged the segregation of the two complexes (task-driven design) or it did not necessarily require segregation (listener-driven design). In both cases, the degree of segregation was assessed by deriving the relative decision weights on the target and masker. Larger differences between the target and masker weights were found as the fundamental frequency difference between the two complexes increased (0.5 – 15 semitones), suggesting that listeners were more successful in selectively attending to the target alone at larger fundamental frequency separations. Although quite different thresholds were obtained for the task-driven and listener-driven designs, the estimates of the decision weights were consistent across the two task designs, indicating that listeners' motivations did not influence the usefulness of the periodicity cue in segregating concurrent sounds.
Noise control options for aircraft floors
Authors: Weisbeck Jeffrey , Gerges Samir , Bustamante Marcelo , Cordioli Julio
Published: April 2012

Aircraft manufactures seek light weight, cost effective technologies to reduce cabin noise levels. Customers and regulatory bodies are demanding lower noise levels in the cabin. Composite light weight structures, used to increase fuel efficiently, often increase input acceleration levels due to their relatively high stiffness and low damping. Therefore, noise control solutions must provide additional attenuation to meet the challenges of fuel efficiency and lower cabin noise levels. Aircraft floors are large radiating bodies that must be addressed. This paper explores noise control options for aircraft floors. Various isolation and damping methods are investigated. Analytical estimates are compared to empirical measurements for a sample aircraft floor.
An experimental characterization of the acoustically dissipative properties of light-weight nanocomposite polyurethane foams augmented with carbon nanotubes
Authors: Willemsen Andrew
Published: April 2012

Flexible, open-cell polymer foams are among the most commonly used and effective materials for passively dissipating noise and vibration. Their unique microcellular structure results in materials which are light weight but still highly absorptive, as well as relatively strong and stiff, making them particularly useful for weight-sensitive applications, such as aircraft cabin noise reduction. "Nanocomposite" polymer foams, which are synthesized from polymer materials containing reinforcing nano-scale fillers, have been shown to have altered morphological and mechanical properties in comparison to conventional counterparts. These same morphological and mechanical properties fundamentally control the acoustic absorption and vibration damping provided by polymer foams. Thus the alteration of these properties by nano-scale reinforcing materials can potentially be exploited to enhance the dissipative properties of these materials. In this study, various composites of polyurethane foam and multi-walled carbon nanotubes were synthesized and then experimentally characterized to observe the effect on noise and vibration dissipation. Sound absorption coefficient and loss factor were measured, along with a number of related material parameters. Results indicate inclusion of carbon nanotubes can increase the ratio of the sound absorption coefficient to weight for polymer foam treatments, dependent on both the carbon nanotube particle size and weight fraction.
Effects of non-linear eddy-airfoil interactions on the acoustic radiation of a thin wing
Authors: Manela Avshalom
Published: April 2012

We study the combined effects of flow unsteadiness (incident vorticity) and external forcing (leading edge animation) on the vibroacoustic radiation of a thin rigid wing. Applying potential flow theory, non-linear coupling between wing motion and flow vorticity trajectory is calculated using the method of conformal mapping. At first, the dynamical problem is formulated and studied. The dynamical description then serves as an effective source term to evaluate the acoustic field. The formulation of the aeroacoustic problem is based on a compact-body acoustic analogy, thus avoiding the traditional difficulty in obtaining the weak acoustic far field from direct numerical simulations. The results identify the airfoil as a dipole-type source, and analyse the significance of non-linear eddy-airfoil coupling on the system acoustic signature. The effect of adding elastic degrees of freedom to the wing, in the form of “passive” linear and torsional springs, is analysed as a mean for monitoring the system acoustic radiation.
Adaptation of English word-final stops into Korean: Effects of English exposure
Authors: Kwon Harim
Published: April 2012

In Korean, word-final stops are never released. When borrowed into Korean, English stop-final words are sometimes, but not always, adapted by epenthesizing /ī/ after the stop. Epenthesis is most frequent for words with coronal stops, that is, words whose stops are arguably most often released [Kang, Phonology 20, 219-273 (2003)]. This study investigates Korean listeners' attention to this sub-phonemic cue in borrowing. Korean listeners are predicted to attend to release cues, but their attention should decrease with their L2 exposure to English. Korean monolinguals, late-bilinguals, and early-bilinguals were tested on English non-word stop-final stimuli with and without releases. Their task was to add a suffix to the novel form; of interest was whether epenthetic /ī/ was inserted during the task. Overall, released stops were twice as likely as unreleased to trigger epenthesis; however, monolinguals were nearly twice as likely as early bilinguals to insert /ī/ after a released stop. This result accords with the “phonological” adaptation of proficient bilinguals [LaCharité and Paradis, Ling. Inquiry 36, 223-258 (2005)]. More proficient bilinguals “know” that English stop release is not contrastive and ignore stop release when adapting English words.
Reciprocal perception of Chinese and Korean affricates and fricatives
Authors: Li Bin , Oh Sunyoung , Shao Jing , Shuai Lan
Published: April 2012

The distinction between lax and tense sounds, as well as aspiration, is employed in classifying Korean affricates and fricatives. Affricates and fricative in Chinese are mainly distinguished in places and aspiration. Little attention has been given on perception of these two types of consonants. This study investigates reciprocal perception of Chinese and Korean affricates and fricatives, by examining how native speakers of the two languages identify each other's consonants at syllable-initial positions. Predictions are made based on how non-native sounds may be assimilated into the native system. First, tense and lax Korean affricates and alveolar fricative may pose difficulty in consonant labeling for Chinese listeners. Korean alveolar fricatives may be perceived as the aspirated alveolar fricative by Chinese listeners. Second, Chinese retroflex and palate-alveolar affricates may be identified as belonging to same categories by Korean speakers. Third, Chinese alveolar and retroflex fricatives may be perceived as same categories when preceding vowel /i/. Predictions are confirmed in most cases. It is also found that vowel contexts play a role in consonant labeling. Assessment of current speech perception models is also discussed using our findings.
Identification of synthesized Mandarin tones by Northern Vietnamese speakers
Authors: Li Bin , Shuai Lan , Pham Thi Thu Ha
Published: April 2012

Tones in Northern Vietnamese are distinguished by pitch variations and phonation types, but falling pitch slopes are not considered as a major cue that its speakers rely on in tonal contrast. This may contribute to difficulties that native speakers of Northern Vietnamese are faced with when learning Mandarin tones, especially the distinction between the level (T1) and the falling (T4) tones. To examine how Northern Vietnamese speakers perceive the distinction between T1 and T4 in Mandarin and how well they adapt phonetic cues underlying the non-native distinction, an ABX identification experiment is carried out on perception of synthesized pitches with two inter-stimuli-intervals (ISI) at 500ms and 1500ms. Results suggest a combined effect of pitch slopes and pitch heights, the former of which claims more robust influence on tone perception. However, a reversed pattern is found when the ISI equals 500ms, where pitch heights exert a stronger effect on tone identification than pitch slopes.
Effects of errorless learning on the acquisition of velopharyngeal movement control
Authors: Wong Andus Wing-Kuen , Whitehill Tara , Ma Estella , Masters Rich
Published: April 2012

The implicit motor learning literature suggests a benefit for learning if errors are minimized during practice. This study investigated whether the same principle holds for learning velopharyngeal movement control. Normal speaking participants learned to produce hypernasal speech in either an errorless learning condition (in which the possibility for errors was limited) or an errorful learning condition (in which the possibility for errors was not limited). Nasality level of the participants' speech was measured by nasometer and reflected by nasalance scores (in %). Errorless learners practiced producing hypernasal speech with a threshold nasalance score of 10% at the beginning, which gradually increased to a threshold of 50% at the end. The same set of threshold targets were presented to errorful learners but in a reversed order. Errors were defined by the proportion of speech with a nasalance score below the threshold. The results showed that, relative to errorful learners, errorless learners displayed fewer errors (50.7% vs. 17.7%) and a higher mean nasalance score (31.3% vs. 46.7%) during the acquisition phase. Furthermore, errorless learners outperformed errorful learners in both retention and novel transfer tests. Acknowledgment: Supported by The University of Hong Kong Strategic Research Theme for Sciences of Learning
On turbo equalization for mobile multi-input multi-output underwater acoustic communications
Authors: Zhao Kexin , Ling Jun , Li Jian
Published: April 2012

This paper focuses on mobile multi-input multi-output (MIMO) underwater acoustic communications (UAC) over double-selective channels subject to both inter-symbol interference and Doppler scaling effects. Temporal resampling is implemented to effectively convert the Doppler scaling effects to Doppler frequency shifts. A variation of the recently proposed generalization of the sparse learning via iterative minimization (GoSLIM) algorithm, referred to as GoSLIM-V, is employed to estimate the frequency modulated acoustic channels. GoSLIM-V is user parameter free and is easy to use in practical applications. This paper also considers Turbo equalization for retrieving the transmitted signal. In particular, this paper reviews the linear minimum mean-squared error (LMMSE) based soft-input soft-output equalizer involved in the Turbo equalization scheme, and adopts a fast implementation of the equalizer that achieves negligible detection performance degradation compared to its direct implementation counterpart. The effectiveness of the considered MIMO UAC scheme is demonstrated using both simulated data and measurements recently acquired during the MACE10 in-water experiment. Acknowledgments: This work was supported in part by the Office of Naval Research (ONR) under Grant No. N00014-10-1-0054. We gratefully acknowledge WHOI for the fruitful collaborations with us to conduct the in-water experimentations and for sharing data with us.
Adaptive multichannel decision feedback equalization using subarray processing
Authors: Preisig James
Published: April 2012

The adaptive multichannel Decision Feedback Equalizer (DFE) has been shown to be an effective algorithm for enabling reliable high rate acoustic communications in complex and time-varying underwater environments. The choice of the number of channels used in an equalizer presents a performance trade-off. The minimal achievable error that can be realized by the equalizer decreases as the number of channels increases. However, an increase in the number of channels increases the number of filter weights that need to be adapted. Thus, the computational complexity of least squares and Kalman type adaptation algorithms is proportional to the number of channels squared. In addition, the averaging interval required by an adaptation algorithm in order to achieve good performance grows linearly with the number of parameters. Thus, an increase in the number of M-DFE channels can reduce the rate of channel fluctuation that can successfully tracked by the M-DFE. The partitioning of an array into sub-arrays which are each independently equalized before combining their outputs can both improve performance and reduce complexity in processing real-world signals. The choice of the size and sensor locations for the subarrays is analyzed. The resulting adaptive subarray multichannel DFE algorithm is compared to other multichannel equalization algorithms.
Experimental studies of support vector machine based blind equalization for shallow water channels
Authors: Fei Yun Wu , Yue Hai Zhou , Feng Tong
Published: April 2012

Due to extended multi-path spread and rapidly changing characteristics, shallow water acoustic channels pose excessive difficulties to the design of high performance underwater communication systems. While classic blind equalization algorithms such as the constant modulus algorithm (CMA) offer potential solutions to tackle the ISI (inter symbol interference) in underwater scenarios without training sequence, slow convergence rate as well as low noise tolerance limits their practical applications. In this paper, blind equalizer based on support vector machine (SVM) is adopted, which makes use of the excellent generalization ability of SVM to accelerate the convergence, and addresses the carrier phase error with embedded phase lock loop (PLL). Experimental SVM blind equalization results conducted in physical shallow water channels show significant performance improvements, demonstrating the effectiveness of the proposed method.
Design and implementation of underwater video transmission system
Authors: Weilin Chen , Hao Ren
Published: April 2012

At first, the paper introduces the basic principles of OFDM system. And then analyzes the structural characteristics of the chip DM642. Taking the design requirements of the system into account, the implementation method in which the main design of underwater image transmission system based on DM642 is accomplished, and the detail designs are given. At the same time, the paper mainly analyzes the address generation process of the frame memory. And then some of the key technologies of PCB designing are introduced. In the software section, the implementations of ODFM technology and algorithm of video compression on the DM642 are highlighted for a specific introduction. Keywords-OFDM; video transmission; H.264; DSP
The influence of the uncertainty of water depth on the inversion of bottom sound speed based on normal mode group velocities in Pekeris waveguides
Authors: Sun Mei , Li Fenghua
Published: April 2012

The normal mode group velocities are widely used in geo-acoustic inversion, and the uncertainty of water depth affects the inversion results. In order to reduce this effect, the law of normal modes' group velocities in Pekeris waveguides versus the water depth and the bottom sound speed is studied. Theoretical and simulative results show that if the frequency is around the Airy frequency of a normal mode, the group velocity of the normal mode is not sensitive to the water depth but sensitive to the bottom sound speed. The group velocities of normal modes are applied to the inversion of the bottom sound speed. Experimental results indicate that the influence of the uncertainty of water depth on the inversion results is significantly reduced if the normal modes whose associated Airy frequencies are near the working frequency.
Assessing shear property variability in shallow water sediments using a wide aperture geophone array
Authors: Schmidt Henrik , Rao Kodali V. , Edson Patrick , Stein Peter
Published: April 2012

The significance of seabed shear properties to low-frequency propagation in shallow water is well established, and since the early 1980's the measurement of the properties of the seismic interface, or Scholte waves, has been recognized as the most direct tool fordetermining the shear properties. In Sep. 2011, an experiment was carried out in Singapore harbor aimed at investigating the excitation of Scholte waves by objects dropped from the surface and impacting the seabed. For that purpose, a 100 m aperture array of 10 ocean bottom seismometers (OBS) with logarithmic spacing was deployed in approximately 16 m of water, in an area with close to range-independent seabed stratification. Spherical and cylindrical objects were equipped with 6 degree-of-freedom motion packages which allowed for accurate measurement of the impact forcing. The objects were dropped onto the seabed at various bearings and distances relative to the array, providing a unique, rich data set which provides the opportunity of estimating the statistic of the seabed shear properties. This paper will describe the experimental setup, and the spatial variability of the phase- and group velocity, and attenuation of the Scholte waves and the associated variability of the seabed geoacoustics will be assessed. [Work supported by DSO National Laboratories, Singapore].
Linking HVAC type and student achievement
Authors: Jaramillo Ana , Ermann Michael
Published: April 2012

Research has long-linked HVAC system type to room noise levels, and it has long-linked room noise levels to student learning. Uninformed design decisions and the absence of policy combine with ineffective execution and insufficient enforcement to produce noisy mechanical systems for schools. Some school HVAC systems place both fans and compressors in the classroom itself, as part of DX units; others utilize remote compressors as part of chillers, but in-room fan motors as part of fan coil units; still other systems use remote AHUs and remote chillers so that neither compressor nor fan motor is exposed to the classroom. This pilot study intends to search for a broader link between HVAC system type and student achievement exams in elementary schools.
Tongji University student design competition—Schools
Authors: Li Jia , Lv Gong , Duan Beiyang , Hu Liyao
Published: April 2012

Armstrong (China) Investment Co., Ltd., with support from Tongji University sponsored a school design competition, and this represents the winning student entry. This competition was intended to encourage students to express their knowledge of architectural acoustics and noise control in the design of a school in which acoustical considerations are of significant importance. Design included considerations of 1) the general architectural building design including both shape and location of the building relative to transportation noise sources, and 2) the specific architectural acoustic design of rooms, including noise control both within and between rooms. The design scenario was for a new primary school designed to replace an older school building at a site near Tongji University. The primary school will include grade levels from 1 to 6, with approximately 1000 pupils. This school building will include normal classrooms (number and size based on student population and design standards), cafeteria, auditorium, library, music rooms, gym, dancing room, etc, as are normally found in such a primary school. The school will consist of a single building, which may be a multi-level building.
Evaluation method of sound field diffusion using sound intensity measurements
Authors: Sugiura Kohta , Omoto Akira
Published: April 2012

Diffuseness of sound field is an essential item for evaluating the characteristics of the sound field. Up to now, several methods for evaluating the degree of diffusion have been proposed. In this study, the method called VSV (Virtual Source Visualizer) is proposed, which effectively visualize direct and reflected sound waves by using the instantaneous intensities in three orthogonal directions obtained from the impulse responses. The VSV casts the projection of dominant reflection onto the virtual sphere, which has a panoramic image of the sound field as a texture. Also, the parameter UAD (Uniformity of Arrival Direction) is introduced that is calculated by using the histogram of the arriving directions of intensities. The effective examination of the degree of diffusion would be expected by the combination of these visualized information from VSV and quantitative evaluation with UAD.
Design of three-dimensional microphone array on polyhedrons
Authors: Lee Jaehyung , Choi Jong-Soo
Published: April 2012

The localization of sound sources in a three dimensional space has been recognized as an important research topic in acoustics. Many acoustic measurement techniques in three-dimensional space have used spherical shape of array to optimize sensor configuration and increase its performance and spatial resolution. In this study, the design of microphone array on polyhedral surfaces is proposed to introduce an easy way of building arrays and to achieve the measurement capability for all direction as a spherical array does. Five symmetrical polyhedrons are used and the simulation results are compared. MEMS microphones are used in arrays and the tests are made in an anechoic environment to validate the performance of arrays. MEMS sensor makes it easy to build a three-dimensional array and enables to implement large number of sensors in a small area. Sensors are built on a printed circuit board (PCB) which becomes a sub-array of polyhedrons. The array output is processed using conventional beamforming method to localize a source's position. The influence of sound wave diffraction around the polyhedron corner on beamformer output is discussed. [Work supported by National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2010-0014978)]
Acoustic scattering measurements by an ultra-broadband transducer using multilayer piezoelectric elements
Authors: Amakasu Kazuo , Mishima Yuka , Mukai Tohru , Sawada Kouichi , Sasakura Toyoki
Published: April 2012

A Langevin-type broadband transducer has been built using multilayer piezoelectric elements. The resonance frequency of this element was 138 kHz, but the quality factor was very low and the transducer had broadband sensitivities due to Langevin structure. The useful frequency band was 20-150 kHz and the beam widths at 38 and 120 kHz were 21.2 and 6.6 degrees, respectively. An echo-sounding system has been constructed using commercially available equipments and the system calibration and acoustic scattering measurements have been conducted using a 2-ms linear-frequency-modulated signal. The system response has been successfully determined using a 20.6-mm-diameter tungsten carbide sphere as a standard target. Furthermore, the target strength (TS) spectrum of a 38.1-mm-diameter tungsten carbide sphere has been measured and the measured TS spectrum was in good agreement with the predicted TS spectrum based on the exact modal series solution. [Work supported by Grant-in-Aid for Scientific Research and TUMSAT.]
A simple resonator technique for determining the acoustic properties of fish schools
Authors: Dolder Craig N. , Wilson Preston S.
Published: April 2012

Acoustic resonators have been used for decades to measure material properties, but only recently have they been applied to determine the effective medium properties of largely inhomogeneous materials. One-dimensional resonators can be used in both a laboratory and field setting to determine the speed and attenuation of acoustic waves through fish schools. Artificial arrays of fish schools are placed in a one-dimensional resonator. After correcting for elastic waveguide effects, the resonances give effective phase speeds and attenuations. The application of this technique to artificial arrays of fish, and how it can be applied to live fish in both a laboratory setting and deployed in the sea will be discussed.
Through-transmission medical imaging using phase-insensitive pyroelectric ultrasonic detectors
Authors: Zeqiri Bajram , Baker Christian , Liang Haidong , Alosa Giuseppe , Wells Peter
Published: April 2012

Ultrasonic Computed Tomography (UCT) has been unable to rival its x-ray counterpart in terms of reliably distinguishing different tissue pathologies. Conventional piezoelectric detectors deployed in UCT are phase-sensitive and it is well established that their use can give rise to phase-cancellation artefacts that mask true tissue structure. In contrast, phase-insensitive detectors are more immune to this effect, although sufficiently sensitive devices for clinical use are not yet available. This paper establishes proof-of-concept for a novel phase-insensitive transducer for UCT. The detector employs an acoustic absorber to convert received acoustic intensity into heat that is subsequently detected using the pyroelectric response of a thin piezoelectric membrane bonded intimately to the absorber. The paper explores UCT application of the phase-insensitive detectors, comparing with traditional detection methods. Results are presented for a range of detector apertures; tomographic reconstruction images being compared using stable two-phase phantoms containing inserts as small as 3 mm. The project has demonstrated that the new detectors are significantly less susceptible to refraction and phase-cancellation artefacts, generating realistic images in situations where conventional techniques were unable to do so. The novel detector holds promise as the basis of a new type of clinical UCT system.
Acoustic diode
Authors: Liang Bin , Guo Xiasheng , Tu Juan , Zhang Dong , Cheng Jianchun
Published: April 2012

Usually, waves can travel just as easily in either direction along a given path. The invention of electric diode, which acts as a one-way filter for the current flux, has marked the beginning of modern electronics and eventually led to worldwide revolutions in many aspects. Similar devices also exist for light and heat transmission. However, it is much more difficult to make such one-way devices for sound waves, another important form of classical wave with even longer research history than electric waves, because of the way sound waves move though a material. Recently, the first model of “acoustic diode” has been demonstrated both theoretically and experimentally to allow the acoustic energy to flow in only one direction. This device was fabricated by coupling a superlattice with a layer of ultrasound contrast agent microbubble suspension. A significant rectifying effect could be observed within two frequency bands at locations that agreed well with theoretical predictions. The development of the “acoustic diode” prototype will inspire the interests and investigations in the more practical and efficient acoustic rectifiers, which should have substantial significance for the applications of ultrasound devices in many practical areas such as medical ultrasound therapy and high resolution imaging.
The environmental noise directive as a catalyst for change in noise policy
Authors: Shilton Simon
Published: April 2012

The Environmental Noise Directive entered into EU legislation in 2002, and subsequently into the national legislation within the 27 Member States. The Directive sets out a strategic framework for a consistent approach to the management of environmental noise within the EC through a cycle of strategic noise mapping, public consultation and action planning. The activities and deliverables required under the END have lead to noise mapping and noise action planning activities on a previously unprecedented scale in many countries, both within Europe and beyond. With the Directive approaching its tenth anniversary it is an appropriate time to look back at whether it has been a catalyst for change in the approach to noise policy within Europe; and how the current ongoing review of the Directive, and proposed development of a common method of assessment, may affect noise policy in the future.
Noise from railway expansion under close watch
Authors: Wong Johnny C. Y. , Ma Geli K. T. , Lam K. H. , Wong C. L.
Published: April 2012

New railway projects are underway in Hong Kong, not only to strengthen transport connections across different districts, but also to provide a high-speed link to enhance Hong Kong's role as the southern gateway to Mainland China. While the new railway systems are expected to provide the much-needed travelling facilities, their construction would inevitably generate noise. These projects are usually subject to tight time-frames and quiet technologies would have to be used when night-works are critically wanted for meeting the deadlines. That major parts of those new railways are constructed in densely populated areas would also increase the technical difficulty in meeting stringent noise criteria. This paper will describe the legislative framework in controlling the construction noise impact in particular from mega railway projects, including (i) various issues considered at the early planning stage by identifying potential noise impacts and recommending effective noise mitigation measures; (ii) the permit systems that govern the construction phase of the projects; and (iii) a transparent monitoring and audit scheme, in order to safeguard the well being of the people being affected.
Numerical study on scattering and absorption by periodically arranged acoustical treatment at oblique incidence
Authors: Cheung Shuk Ching , Wang Chunqi , Huang Lixi
Published: April 2012

The propagation of sound over an impedance strip has been a topic of interest in sound abatement design. Excess absorption by the periodical arrangement of two or more distinct impedance conditions has been shown by various theoretical and experimental studies. It is believed that the scattering by the impedance discontinuities can enhance the absorption in some designs. This gives motivation to design a more elaborate set of impedance distribution within one periodic module. In this study, the scattering and absorption by periodically-arranged acoustical treatment at oblique incidence is investigated using the spectral method of Chebyshev collocation. The effects on the sound absorption and reflection by the length of the repeating unit, the angle of incidence and scattering characteristics due to the discontinuities of the acoustical impedance are analyzed. Central to the method is the derivation of out-going waves which allows scattered sound of all directions to leave the computational domain without reflection. The full picture of scattering is captured and analyzed using a rather coarse set of grid suitable for further optimization studies.
High frequency ultrasonic particle sorting
Authors: Shung K. Kirk , Lee Changyang
Published: April 2012

Single particle sorting devices have been used in bioassay compartmentalization and cell sorting. Fluorescence-activated cell sorting (FACS) is a well-known example. This paper presents an acoustically driven particle sorting device integrated with a poly(dimethyl) siloxane (PDMS) microfluidic channel. The device consists of two independent and sequential processes, acoustic sensing and sorting. Hydrodynamically focused lipid microspheres flowing in the channel are non-invasively sensed by a low intensity high frequency ultrasonic beam at 30 MHz for quantitative measurement of backscatter. Following sensing, the particles are sorted via acoustic radiation force or acoustic tweezing by a high intensity beam generated by the same transducer. The device has been successfully used to separate a mixture of 50 μm and 100 μm lipid spheres by size. Its performance and potential applications will be discussed in this paper.
Particle sorting using an oscillating microbubble
Authors: Neild Adrian , Rogers Priscilla , Xu Lin
Published: April 2012

The ability to sort suspended matter within complex fluid samples is a key part of the functionality of Lab-on-a-chip devices. This study investigates the use of microbubbles to achieve this task. Bubbles which vibrate due to acoustic excitation are very effective at concentrating energy which can cause strong acoustic microstreaming. This fluid motion brings particles very close to the bubbles' surface. When in close proximity to the bubble the Bjerknes force arising between the particle and bubble can be large enough to pull the particle out of the swirling flow which characterizes acoustic streaming. If this occurs the particle is captured on the bubble surface, otherwise the force balance, which is size and density dependent, is such that the particle will remain in the streaming flow, apparently rejected by the bubble. The bubbles can be excited at their resonance or by the presence of an acoustic standing wave which can be created by exciting the fluid chamber at resonance. In the latter case, the interaction between the standing wave and particles can be used to bring more particles into the vicinity of the bubble.
Surface acoustic waves (SAW) accelerated microfluidic mixing for improved microcalorimetry in biochips
Authors: Renaudin Alan , Béland Rémy , Cloarec Jean-Pierre , Chevolot Yann , Aimez Vincent , Charette Paul G.
Published: April 2012

By measuring very small local temperature changes, microcalorimetry is used to determine the rates of energy released or absorbed during biochemical reactions. The measurement signal-to-noise ratio can be significantly increased by accelerating the reaction kinetics by active microfluidic mixing. We present a biochip incorporating a self-referencing droplet-based microreactor consisting of a thermopile-based microcalorimeter (50 Ni/Au thermocouples in series) on a glass substrate with a surface acoustic wave (SAW)-based microfluidic mixing system on a LiNbO3 piezoelectric substrate. In our design, the SAW mechanical energy is transmitted from the piezoelectric substrate through the glass substrate to the droplets via a water film which acts as a pseudo mechanical impedance matching layer. The cumulative energy released by a standard calorimetric test reaction (sucrose dilution) is measured with the system. Results show that, by overcoming the diffusion-limited reaction rate, SAW-accelerated mixing in the droplets increases the thermal power released during the experiment by a factor 2, increasing the measurement SNR by the same factor. This enthalpy measurement accuracy improvement makes the system well-suited to sensitive thermodynamic measurements on biochip devices.
Similarity and cluster analysis on magnitudes of individual head-related transfer functions
Authors: Xie Bosun , Zhong Xiaoli
Published: April 2012

Although head-related transfer functions (HRTFs) vary with individuals, non-individualized HRTFs are typically employed in virtual auditory display (VAD) due to the difficulty in measuring individual HRTFs. Similarity among the HRTFs of different individuals allows for customizing a matched set of HRTFs for a user from an existing database and thereby improving performance of VADs. The first step of HRTF customization is evaluation of the similarities among individual HRTFs. In the present work, based on a HRTF database of 52 Chinese subjects, the similarities are evaluated by calculating the directional-mean of normalized cross-correlation coefficient (MCC) of HRTF magnitudes between each pair of subjects and then applying cluster analysis to the resultant MCC. The results indicate that MCC depends on subject pair with values ranging from 0.934 to 0.562 (mean 0.842) and from 0.948 to 0.635 (mean 0.863) for the left and right ear, respectively. HRTF magnitudes for most subjects can be classified into six to eight clusters and represented by the corresponding cluster centers. Some singleton clusters are also observed on a few subjects, which reflect the diversity in HRTFs and should be careful in practice. Psychoacoustic experiment also validates above analyses.
Fault diagnosis method using support vector machine and errors-in-variables for rotating machines
Authors: Han Hyungseob , Chong Uipil
Published: April 2012

As rotating machines play an important role in industrial applications such as aeronautical, naval and automotive industries, many researchers have developed various condition monitoring systems and fault diagnosis systems by applying artificial neural networks. In order to increase performance of a classifier based on a neural network, it is most important to extract significant features of measured signals and to apply suitable features into a diagnosis system according to the types of the signals. Therefore, this paper proposes a neural-network-based fault diagnosis method combining Support Vector Machines (SVM) as a classifier and AR coefficients as feature vectors by Errors-In Variables (EIV) analysis. The system extracted feature vectors from sound, vibration and current signals and evaluated the suitability of feature vectors depending on the classification results and training error rates by changing AR order and adding noise. From the experimental results, it is concluded that classification results using feature vectors by EIV analysis indicate more than 90% stably for less than 10 orders and noise effect comparing to linear predictive coding (LPC).
Research on engine exhaust noise control based on the neural network
Authors: Wang Ye , Liu Xueguang , Yin Changchun , Zhu Min
Published: April 2012

A new type of semi-active control method which called bypass duct silencer is proposed. For the sake of reducing the exhaust noise by 15 dB, the relationship among the engine speed, the exhaust temperature and the structure of the bypass duct silencer is got. Then the bypass duct silencer which can change the internal structure of the silencer is present. The silencer contains several valves, which could control the flowing direction of sound wave aiming to neutralize sound wave in the downstream intersection of the duct. When the BP neural network structure was trained, the engine speed and the exhaust temperature measured were considered as input signals, meanwhile, the controlling situation of the valves was considered as output signal. The network structure is certain when the error of this method lies within a tolerable range the thresholds and weights are determined. The trained neural network structure could be used to reduce the exhaust noise in practical application.
Research on hybrid isolator technique
Authors: Liu Xueguang , Wang Ye , Zhang Bin
Published: April 2012

This paper presents a new hybrid isolator technique that composes of passive vibration device and active actuator. It contains the advantages of both active and passive isolation system. During the optimization design, the passive vibration isolator as cylindrical rubber is designed, then the active actuator is designed as electromagnetic actuator with advantages of compact construction and larger forces. After manufacturing the prototype designed, the vibration active control experiment is carried out, which can verify the hybrid isolator's performance. During the mono-layer active control experiment, vibration of the upper layer mass reduced about 29dB~40dB. In the two-stage experiment, it has gained a good effect in both single and double frequency excitation. It means that the hybrid isolator technique designed has good performance of anti-vibration in practical application.
Preceding non-linguistic stimuli affect categorisation of Swedish plosives
Authors: Bjerva Johannes , Marklund Ellen , Engdahl Johan , Tengstrand Lisa , Lacerda Francisco
Published: April 2012

Speech perception is highly context-dependent. Sounds preceding speech stimuli affect how listeners categorise the stimuli, regardless of whether the context consists of speech or non-speech. This effect is acoustically contrastive; a preceding context with high-frequency acoustic energy tends to skew categorisation towards speech sounds possessing lower-frequency acoustic energy and vice versa (Mann, 1980; Holt, Lotto, Kluender, 2000; Holt, 2005). Partially replicating Holt's study from 2005, the present study investigates the effect of non-linguistic contexts in different frequency bands on speech categorisation. Adult participants (n=15) were exposed to Swedish syllables from a speech continuum ranging from /da/ to /ga/ varying in the onset frequencies of the second and third formants in equal steps. Contexts preceding the speech stimuli consisted of sequences of sine tones distributed in different frequency bands: high, mid and low. Participants were asked to categorise the syllables as /da/ or /ga/. As hypothesised, high frequency contexts shift the category boundary towards /da/, while lower frequency contexts shift the boundary towards /ga/, compared to the mid frequency context.
A cross-linguistic study of the effect of perceived gender on the categorization of children's vowels
Authors: Munson Benjamin
Published: April 2012

Previous research has shown that listeners classify acoustically gender-ambiguous vowels differently depending on whether they believe the speaker to be a man or a woman (Johnson, Strand, & D'Imperio, 1999). In real-world listening situations, this tendency could be especially pronounced in the perception of vowels produced by children, as children's voices are inherently gender-ambiguous (Perry, Ohde, & Ashmead, 2001). Given Johnson et al.'s findings, we would predict that adults would categorize children's vowels differently depending on whether they believe the speaker to bes male or female. To examine this hypothesis, a set of experiments was conducted in which native speakers of Cantonese, Japanese, and English categorized a series of synthetic vowels (Menard et al., 2006). These were generated using an articulatory synthesizer, and were meant to represent the vocal tracts of newborn children, 2-, 4-, 5-, 10-, 16-, and 21-year olds. Adults categorized these vowels and provided judgments of the perceived gender and age of the speakers. Preliminary results suggest that speakers of English categorize vowels differently depending on whether they judge the child to be male or female. This tendency is especially marked for the most gender-ambiguous stimulus set, those based on the 10-year-old vocal tract.
The effect of training structure on perceptual learning of accented speech
Authors: Tzeng Christina Y. , Nygaard Lynne C.
Published: April 2012

Although previous research suggests that high variability training facilitates perceptual learning of systematic variation in speech, the extent to which the organization of training materials affects this learning remains relatively unexplored. The present study examined the role of training structure on the perceptual learning of speaker-independent properties of Spanish-accented speech. During training, native adult speakers of American English transcribed sentences spoken in English by four native Spanish-speaking adults. Training stimuli were presented to listeners either grouped by speaker, sentence, or randomized with respect to sentence and speaker. At test, listeners transcribed novel sentences produced by four unfamiliar Spanish-accented speakers. Transcription performance at test was found to vary as a function of the organization of training materials. Listeners transcribed test sentences more accurately when training sentences were randomized relative to when training sentences were grouped by speaker or when listeners received no training. Test performance when training sentences were grouped by sentence was intermediate. These findings suggest that variable training structure may direct listeners' attention to accent-general properties of speech, allowing for comparison across speakers' voices and linguistic content, and generalization of learning to unfamiliar accented speakers.
Understanding concurrent speech is not impaired by removal of spectro-temporal overlap
Authors: Kleczkowski Piotr , Pluta Marek
Published: April 2012

Removal of spectro-temporal overlap is the operation performed on acoustic signals in the time-frequency domain. It can be seen as extreme energetic masking, where the masking threshold is equal to the level of the masker. In Experiment 1 the triplets of words were presented concurrently with reversed speech of four speakers. The recognition of words with and without spectro-temporal overlap was compared. In Experiment 2, understanding of five words spoken simultaneously, with and without spectro-temporal overlap was compared. Over 50 subjects took part in both experiments. The joint results showed no significant difference between unprocessed presentation and the processed one, where spectro-temporal overlap was removed. This is rather surprising, as the amount of information provided to the ear was considerably reduced in the processed case.
Two kinds of timbre representations and its application into acoustic target classification
Authors: Chen Kean , Liang Yong , Du Liangfen , Chen Jue , Wu Ying , Wang Huanrong
Published: April 2012

Being an important auditory attribute of sound, timbre exhibits great potential for classifying sound source and its suitable representation and parameterization are crucial for feature extraction. In this study, we express environmental sound's timbre in terms of verbal description and its projection in independent space, which are respectively referred to as Natural Timbre (NT) and Essential Timbre (ET). In this study, such two kinds of timbre expressions are applied to acoustic target recognition using synthesized steady-state underwater noise with two subjective rating experiments. First a semantic differential test is conducted and the NT-based target identification rates are achieved by forced clustering; then a paired comparison experiment is carried out to get the ET-based identification rates. Finally, the recognition performances for two kinds of timbre representations are compared and its advantages are discussed in association with feature extraction and acoustic target recognition.