bluuebunny/crossref_metadata_2025 huggingface dataset:
Subjective evaluation of 5.1 channel signals' reproduction by two loudspeakers with small spacing angle
Authors: Rao Dan , Ming Fang
Published: April 2012

In some circumstances (such as looking at TV), it is needed to use two loudspeakers with small spacing angle to reproduce multi-channel surround sound. The performance of reproduction with closely spaced loudspeakers was concerned. In this paper, the performances of two-loudspeaker reproduction were evaluated by a subjective listening test. Using 5.1-channel signals' reproduction with standard five-loudspeaker arrangement as reference, two reproduction methods, downmixing and virtual reproduction were graded according to three attributes, spatial impression, timbre and global impression with picture. Five-grade impairment scale was adopted in test assessment and 17 subjects with listening experiences participated in the test. Test results show that the performance of downmixing method is degraded with decreasing spacing angle of loudspeaker pair, and the performance of virtual reproduction method almost is not affected by spacing angle within the range of less than 15 degrees. In addition, subjective score of virtual reproduction is better than that of downmixing reproduction in all three experimental spacing angels. Therefore, virtual reproduction method can improve the two-loudspeaker reproduction performance of multi-channel surround sound signal compared to the common downmixing method.
Detection of spectral changes induced by a break in sound correlation in younger adults and older adults
Authors: Qu Tianshu , Cao Shuyang , Chen Xun , Huang Ying , Wu Xihong , Schneider Bruce , Li Liang
Published: April 2012

Detecting a transient break in correlation (BIC) between correlated sounds is much easier when presented over two loudspeakers than when presented over two headphones. However, older adults benefit less than younger adults from a change from headphone to loudspeaker presentation (Ear and Hearing, (30) 273-286, 2009), suggesting an age-related reduction in sensitivity to monaural and/or binaural spectral cues provided by comb filtering. In this study, the monaural spectral cues present in the sound field were isolated and extracted, and then presented over headphones to younger adults and older adults with clinically normal hearing. Compared to younger adults, older adults exhibited a reduced sensitivity to the monaural spectral cues, particularly when an inter-loudspeaker time interval was introduced.
The sound insulation of composite cylindrical shells; a comparison between a laminated and a sandwich cylinder
Authors: Yuan Chongxin , Roozen Bert , Bergsma Otto , Beukers Adriaan
Published: April 2012

The fuselages of aircraft are modeled as cylinders in this paper, and the sound insulations of a sandwich cylinder and a laminated cylinder are studied both experimentally and numerically. The cylinders are excited by an acoustic pressure and a mechanical force respectively. Results show that under acoustic excitation, the sandwich cylinder and the laminated one have a similar sound insulation below 3000 Hz, but the sandwich cylinder has a much larger sound insulation at higher frequencies. Under mechanical excitation, the sandwich cylinder is also more beneficial, showing a larger sound insulation above 800 Hz.
Comparative analysis on acoustic radiation modes of typical structures
Authors: Dai Lu , Yang Tiejun , Du Jingtao , Sun Yao , Dong Jianchao , Li Xinhui
Published: April 2012

Acoustic radiation modes have received increasing attention in the areas of structural acoustic radiation and active structural acoustic control during the past few years. In this paper, a comparative study on the acoustic radiation modes of several typical structures and their associated radiation efficiencies is presented. The present work is also undertaken to extend the acoustic radiation modes into more complex structures, i.e. a thin cylindrical shell, since it was rare described in the literatures. The two analytic approaches for deriving acoustic radiation modes are reviewed briefly first. Numerical examples and comparative analysis are performed from one-dimensional problem to two-dimensional and three-dimensional problems. A grouping characteristic of acoustic radiation modes and their corresponding radiation efficiencies is observed. The shapes of the acoustic radiation modes follow the order of uniform variation, linear, quadratic and high-order variation. It is interesting that the acoustic radiation modes of a cylindrical shell exhibit symmetric and anti-symmetric shapes in the circumferential direction, similarly to its structural modes.
Effects of perceptual training on the ability of elderly adults of Japanese speakers to identify American English /r/-/l/ phonetic contrasts
Authors: Kubo Rieko , Akahane-Yamada Reiko , Akagi Masato
Published: April 2012

Previous research has demonstrated that auditory perceptual training on young adults improves their ability to identify phonological contrast in foreign languages. However, most research has focused on college-age adults, and little research has considered age-related changes among adults. In this study, training to identify American-English /r/-/l/ was conducted with Japanese speakers in their 30s, 40s, 50s, and 60s. The pretest-post-test design was used for comparing the results with those of young adults (Lively, 1994). As a result of training, although the identification performances improved in every age group, there was an age-related gradual decline in the improvements. Analyses concerning phonetic environments revealed that older adults had more difficulty learning targets in initial consonant clusters than did the younger ones, while had comparable improvements in final position. Komaki et al. (1999) suggested that as a result of listeners' language-specific perceptual strategies, Japanese speakers identify targets least accurately in initial consonant clusters and most accurately in final position. This trend in identification is seen in older adults' learning. These results suggest that the ability to learn new phonological categories is preserved in normal aging from the 30s to 60s and that older adults are more dependent on their first language in learning.
Distributions of [r]-deletion and [w]-substitution in English C[r] clusters by Cantonese speakers
Authors: Lan Yizhou , Oh Sunyoung
Published: April 2012

Literature shows that Cantonese speakers often delete [r] in C[r] clusters in English (e.g. [pɪnt] for “print”). However, based on our observation, [w] substitution of [r] is also apparent during speech. Experiment was conducted to see the distribution of deletion and substitution and investigated the effects of the place of articulation and syllable structure on the distribution of C[r] production. Ten non-English-major university students participated in the study. Stimuli were randomized and repeated 10 times in a passage, contrasting consonants between open and closed syllables (C[r]V vs. C1[r]VC1) in three vowel conditions (/i, a, u/). Two-way ANOVA was used for statistics. Preliminary results show that overall, substitution is more dominant than deletion for the clusters, particularly with velars. Deletion, though much less than substitution, is only observed with bilabials whereas alveolar clusters are mostly pronounced correctly. Also, substitution and deletion tend to occur more in closed syllables than in open syllables. Findings suggest that such distributions are based on the speakers' articulatory strategy of gestural economy.
Cross-dialect and cross-language differences in perception of vowels: A multidimensional scaling study
Authors: Yang Jing , Fox Robert Allen , Jacewicz Ewa
Published: April 2012

This study examines the perceptual responses to vowels in two regional varieties of American English typical of Central Ohio (OH) and Western North Carolina (NC). Listeners are monolingual local speakers of each dialect and Mandarin-English bilinguals in Columbus OH. The questions are (1) how English listeners perceive acoustic variations in vowel quality differences not found in their own dialect and (2) whether bilingual listeners are sensitive to such differences not found in their native language. In a multidimensional scaling study, we investigate whether listeners make these perceptual decisions on the basis of acoustic properties or categorical properties of these vowels. Each listener was presented with two sets of 13 vowels /i ɪ e ɛ æ u ʊ o ɔ ɑ ɔɪ aɪ aʊ/ in a /hVd/ syllable. One set was produced by an OH male speaker and the other by a NC male speaker. Listeners rated all possible vowel pairs from one set only on a nine-point similarity/dissimilarity scale (there were two subsets of listeners in each group). The resulting dissimilarity matrices were analyzed using INDSCAL. Results will be discussed in terms of differences in perceptual dimensions (vowel coordinates and subject weights) as a function of dialect and L2 background.
Vowel production before 8 years of age: A longitudinal formant analysis
Authors: Chen Li-mei , Lin Ya-Chiang , Kuo Tzu-Wen
Published: April 2012

Vowel production in two Mandarin-learning children was recorded from birth to 8 years old. The present study is the report of the 8th year. Major findings are: 1) Starting from 5 years of age, vowels with nasal endings show similar frequency as diphthongs. Girl subject used vowels with nasal endings more frequently than boy subject; 2) Decrease of F1 F2 values is continuously observed in boy subject. As to girl subject, up to 8 years of age, no obvious change in formant values was found; 3) F1 values are more stable than F2 values, especially in [i, u]. They appeared to acquire jaw movement sooner than tongue movement. Although a general trend of reduction in variability can be found from 4 years on, there seems to be more fluctuation of F2 values at 7-8 years of age in both subjects; 4) The trend of reduction of vowel areas was found to start at around 4 years old for boy and at 6 years old for girl; 5) No obvious decline in fundamental frequencies was found at 7-8 years of age in both subjects. This investigation was supported through funds from National Science Council in Taiwan (NSC 99-2410-H-006 -102-MY2).
Effects of musical experience on learning lexical tone categories
Authors: Zhao Tian , Kuhl Patricia
Published: April 2012

The relationship between music and speech processing is of great interest. Lexical tones, contrastive pitch-modulation patterns at the word level, are an ideal tool to explore these relations. Previous studies suggest that musicians exhibit an advantage in discriminating lexical tones. The current study aims to explore whether having extensive musical training is associated with the ability to form robust lexical tone categories given highly variable natural speech tokens. A continuum of pitch contours was created with Mandarin Tone 2 and Tone 3 as the endpoints (see Zhao, Wright, & Kuhl ASA abstract). First, 20 monolingual English musicians and 20 monolingual English non-musicians completed identification and discrimination tasks that established individuals' perceptual boundaries on the continuum. Then, half of the musicians and half of the non-musicians were randomly assigned to an 8-session perceptual training procedure. Lastly, all subjects completed identification and discrimination tasks both with old and new stimuli to examine changes in perceptual boundaries and generalization. Results will be considered in terms of theories relating speech and music processing. [Research supported by NIH and NSF.]
Phonetic characteristics of school students in Chinese dialect regions
Authors: Liu Yali , Meng Zihou
Published: April 2012

To study the factors which can affect Mandarin-learning of school students in dialect regions, parents, teachers and school students are investigated by questionnaire respectively. Based on the questionnaire, two attributes are obtained through factor analysis, including Mandarin-learning environment and the correlation of Mandarin and dialect. The speech database in Mandarin dialect is recorded, in which there are 455 speakers in total, including 235 male speakers and 220 female speakers (aged from 8 to 18 years old). The database falls into three groups by age. The first group is from 7 to 11 years old; the second is from 12 to 13 years old; the third is from 14 to 16 years old. The acoustic characteristics of initials, finals, F0 and tones are investigated under the three groups. For initials, peaks of high frequencies are extracted. For finals, formant pattern charts are given. The development of F0 and patterns of contour tones for a syllable are summarized. Based on the result of the factor analysis and acoustic characteristics, the patterns of phonetic errors of different age during Mandarin-learning are proposed. The phonetic analysis may provide some references for assessment and improvement of Mandarin-learning for teenagers in dialect regions.
Cantonese Pronunciation among Hong Kong speakers and American Born Chinese speakers
Authors: Cho Sandy , Koenig Laura , Shi Lu Feng
Published: April 2012

This study contrasts the production of Cantonese words between native (Hong Kong) immigrant speakers of the language and native first or second generation American-born Cantonese speakers. The word lists were constructed to sample across the tone space and vowel space. Multiple recordings were recorded at different intervals in order to assess variability in sound production. Of particular interest was whether the American-born speakers showed greater variability than the Hong Kong speakers. Vowel formant frequencies and tonal patterns, measured by fundamental frequency contours, were compared between the Hong Kong speakers and the American born speakers. In addition, we evaluated the presence of “lazy tones” in the two groups. This data adds to the sparse literature on Cantonese speakers in America.
Low complexity estimation and equalization of doubly spread underwater acoustic channels
Authors: Zeng Wen-Jun , Xu Wen
Published: April 2012

Underwater acoustic channels are characterized by limited bandwidth, long multipath delay spread, and severe time variation, which make reliable and high-rate communication challenging. Channel-estimate-based equalization is a key technique for compensating for distortions introduced by the channel. In this paper, low complexity algorithms for estimation and equalization of doubly spread underwater acoustic channels are presented. By exploiting the sparsity in the delay-Doppler domain, a fast projected gradient method (FPGM) is developed for estimating the delay-Doppler spread function of a time-varying channel. The FPGM formulates sparse channel estimation as a complex-valued convex optimization using an ℓ1-norm constraint. Unlike the conventional methods that split the complex variables into their real and imaginary parts, the FPGM directly handles the complex variables as a whole. A unified framework, which includes the time-reversal, linear MMSE, and decision feedback equalizer, is also proposed for fast equalization of doubly spread channels. By exploiting the special block Toeplitz-like structure of the coefficient matrix, the computational complexity of channel estimation and equalization is on the order of LNlog N, where L is the dimension of the Doppler shift and N is the signal length. [Work supported by Chinese 863 high-tech program under Grant 2009AA093601]
Sequential analysis for underwater communications
Authors: Morozov Andrey , Green Dale
Published: April 2012

The state-of-the-art in high-rate, single-carrier wideband signaling for acoustic communications is represented by the decision feedback equalizer (DFE). Though often effective, its performance is far from the optimal obtained from soft decision maximum a posteriori probability (MAP) and maximum-likelihood sequence detectors (MLSD). While these algorithms have optimal performance, their complexity increases exponentially with the duration of the channel impulse response. In practice, such methods are only used for multicarrier modulation, after mode filtering or other form of channel shortening, time-spatial pre-processing equalization. The optimal joint channel estimation and data decoding algorithm is derived and analyzed. The combination of pre-processing, channel response shortening equalization, and joint channel and data recovery have shown excellent performance in shallow water acoustic communications experiments. A sequential estimation alternative to MLSD-based decoding is “almost” as effective in a probability sense, given a modest increase in signal-to-noise ratio (SNR). That approach combines very high performance with a small computational burden relative to the MLSD approach. The practical result of the paper is the investigation of the replacement of the DFE with a sequential implementation (FANO) of a likelihood sequence estimator. Comparative performance of the two using at-sea experiments in very shallow water is provided.
Numerical simulation and experiment of the shallow water communication channel with time varying multipath effect using time reversal mirror
Authors: Lin Yi-Wei , Andhi Indira Kusuma I Putu , Too Gee-Pinn
Published: April 2012

The underwater communication channels limitations are mainly due to multipath effect and ambient noise. Multipath effect is a serious problem when underwater communication in the shallow water is considered, because it induced severe inter-symbol interference (ISI). Time reversal mirror (TRM) has been widely used in the underwater communication to overcome the multipath effect by evaluating impulse response function (IRF); and further, it can reduce bit error rate (BER). In this paper, underwater communication channel is explored in 175 m x 8 m x 4 m Towing Tank. Both numerical simulation and experimental are conducted to verify the effect of time varying multipath. Image method and statistic analysis are used to simulate the time varying multipath effect due to wave propagation in the shallow water. The BER caused by time varying multipath effect is evaluated by adding arrival time lag variation and arrival signal amplitude variation in impulse response function. The results show that time reversal process is effective to reduce BER and overcome the time varying multipath effect.
Coherent communications in snapping-shrimp dominated ambient noise environments
Authors: Chitre Mandar , Mahmood Ahmed , Armand Marc
Published: April 2012

The additive white Gaussian noise (AWGN) model is commonly used in the development of communication systems, and adequately models many noisy environments. However the impulsive noise from snapping shrimp is poorly approximated by this model. The mismatch in model has an adverse impact on the performance of conventional communication systems operating in warm shallow waters. The AWGN model may be replaced by the more general additive white symmetric α-stable noise (AWSαSN) model, which better approximates the heavy tailed noise due to snapping shrimp. When converted to the complex baseband representation, the resulting noise for the AWSαSN case is radically different from its Gaussian counterpart. In this talk some properties of baseband noise for the general AWSαSN case are investigated. These properties can be used to guide design decisions for coherent communication systems operating in warm shallow waters. The baseband noise is generally not isotropic and furthermore the real and imaginary components may be dependent. By varying certain physical parameters different non-isotropic distributions may be attained. The resulting properties can be exploited to design communication systems that are able to provide robust performance in the presence of snapping shrimp noise.
Recent experiment results of long-range time-reversal communication in deep ocean
Authors: Shimura Takuya , Ochi Hiroshi , Watanabe Yoshitaka
Published: April 2012

In the Japan Agency for Marine-Earth Sicence and Technololgy (JAMSTEC), a project to develop new autonomous underwater vehicle (AUV) is being planned, which will have the capability to cruise long distances over several hundred kilometers. Achieving acoustic communication with such a long-range AUV, even at a low data transmission rate, will be important. Time reversal is an attractive solution for such a long-range communication, by converging multipath signals and decreasing intersymbol interference (ISI). Thus, we have researched on time-reversal communication in the deep ocean, have proposed a method of combining time reversal and adaptive equalization, and have executed various at-sea experiments in the deep ocean. In the first experiments, both active and passive time-reversal communication were performed at the range of 10 km and it was shown that time reversal could enable communication under many multipath interferences. The subsequent experiments were carried out in various ranges for passive time-reversal communication. In our latest trial, communication at the range up to 1,000 km was demonstrated at the data rate of 100 bps at the frequency of 500 Hz. In this paper, the results of these experiments are described.
Time reversal based channel tracking for underwater acoustic communications
Authors: Xia Menglu , Xu Wen
Published: April 2012

Time reversal processing (TRP) has been proved to achieve temporal compressing when the waveguide environment is invariant. TRP has been exploited in underwater acoustic communications as it can, without any knowledge of the channel, compensate severe inter-symbol interferences (ISI) that are caused by complex multi-path propagation. However, environmental variations occur almost all the time when conducting acoustic communications in the real ocean, and indeed become one of the main factors determining the communication performance. Since the channel is time variant, the ISI can not be removed completely through time reversal. In the present paper, a channel tracking method is developed by using this leftover ISI after time reversal processing in a slowly time-variant environment. Change of the channel response structure is estimated in terms of time-delay shift and attenuation differences. Simulations of the method applied to synthetic data and field experimental results are both provided to demonstrate the method's feasibility. [Work supported by Chinese 863 high-tech program under Grant 2009AA093601]
Study on underwater acoustic voice communication system for divers
Authors: Lei Lihua , Xu Feng
Published: April 2012

This paper describes the design and sea trail of an underwater acoustic speech transmission system for the continuously increasing need for diver communications. The input speech signal is compressed down to 2.4k bit/s using a MELP (mixed excited linear prediction) coder. The bit rate is 6k bit/s after channel coding and frame synchronization. A QPSK modulation with differential encoding was chosen to transmit the useful signal. To overcome the phase fluctuation and multi-path effects caused underwater acoustic channel we employed a scheme where phase synchronization and fractional spaced Decision Feedback Equalization (DFE) were jointly optimized by RLS algorithm in the receiver. Two kinds of error correcting schemes were used including convolutional codes (CC) and Reed Solomon (RS) block codes. The whole system has been conducted successfully in very shallow water environments and the short range horizontal acoustic voice communication link performances are evaluated.
Doppler experiment for shallow underwater acoustic communication using QPSK and turbo corder
Authors: Ikeda Teiichiro , Hashiba Kunio , Takano Shinta , Imai Ryusuke , Nanri Mitsuhiko
Published: April 2012

A continuous data link under shallow and towing conditions is essential for UUV operation. In shallow water, inter-symbol interference (ISI) due to multipath fading strongly distorts the carrier signal. In addition, the phase of the signals shifts considerably due to the Doppler shift at a high relative speed (~5-kt) between the mother ship and the UUV. The communication performance degrades significantly compared to static communication. Actually, a 1-kt relative speed between the transmitter and receiver causes a phase shift of more than 2 Mπ within 1000 symbols of transported data. In this study, we investigated QPSK acoustic telecommunication systems that incorporate a Turbo corder and digital phase lock loop (DPLL) for the Doppler shift compensation. A towing experiment was conducted in shallow water, and the performance of the system was evaluated. When the receiver was 3 m deep, at speeds of 1.49 and 2.02 kt, we see a considerable number of errors. When the receiver depth was 15 m from the surface, all of the transmitted data were completely reproduced after applying our acoustic communication algorithm.
A numerical study of interferometric imaging in underwater acoustics
Authors: Ying Yingzi , Wu Ying
Published: April 2012

Time reversal acoustics has long been a prevailing concept and became fruitful in underwater acoustics community. While the interferometric imaging, or interferometry, which migrates the cross-correlations over suitable time interval of the traces received at the array, is mostly used in the reconstruction of subsurface geometry in exploration geophysics. In this numerical study, the interferometric imaging method is used to localize the active underwater targets. The intrinsic relationship between the interferometry and time reversal is revealed by back-propagating the received and time reversed signals into a fictitious waveguide model. When the frequency decoherent parameter is infinitely small, the imaging estimator becomes the conventional Bartlett matched field processing, whereas the Kirchhoff migration is achieved when frequency decoherent parameter is equal to the full band. A comparison of the imaging quality with different frequency decoherent parameters is performed through the normal-mode based simulation, and the results show the interferometric imaging is feasible and effective in underwater acoustics. This research was supported by KAUST start-up package.
Precise and efficient localization of room reflections using compact microphone arrays
Authors: Kellermann Walter , Mabande Edwin , Sun Haohai , Kowalczyk Konrad
Published: April 2012

Recent works have shown that precise localization of dominant reflections in acoustic environments can be achieved even by relatively small arrays if advanced beamforming concepts are employed. To this end subspace-based and steered beamformers-based localization techniques are implemented in the so-called eigenbeam domain leading to eigenbeam (EB)-ESPRIT, EB-MUSIC, and EB-Minimum Variance Distortionless Response (EB-MVDR) beamforming. The resulting algorithms can be deployed with small off-the-shelf spherical microphone arrays and can then lead to acoustic maps using only a single multichannel recording. They can furthermore be used as a tool for efficiently inferring the geometry of a room. In this contribution we will present a comparison of several methods in real-world scenarios and illustrate their distinctive properties, including robustness issues and known limitations.
Effects of coupling between loudspeaker and wall on impulse response measurement
Authors: Wu Di , Mo Fangshuo , Ge Jianmin
Published: April 2012

Impulse response measurement constitutes a major part in room acoustical measurement. To measure an impulse response, the loudspeaker issues a relatively long signal, which is counteracted by the reflected sound field, and then its radiation impedance would undergo a change. Volume velocity generated by the loudspeaker is determined not only by excitation signal and loudspeaker parameters, but also by the coupling between the loudspeaker and the walls. Calculating the impulse response by deconvolution of sound pressure and excitation signal introduces a bias. The paper adopts an analogy of electric, force and acoustics, fully analyzing the effect of change in radiation impedance on impulse response measurement, and runs an experiment to verify the effects.
Objective sound field analysis based on the coherence estimated from two microphone signals
Authors: Kuster Martin
Published: April 2012

The coherence estimate function represents the coherence function for discrete-time and finite-length time signals. In order to avoid bias error in the estimation of the required spectral densities, there is always an averaging mechanism in either time, frequency or space involved. This averaging has important consequences in room acoustics because diffuse field equations are then applicable to reverberant fields. It will be shown how the coherence estimates from diffuse and reverberant fields differ as a function of the averaging constants. For reverberant fields it will further be shown that the dependence between coherence estimate and averaging constants is defined by the direct-to-reverberant energy ratio and the reverberation time. Finally, the existing analytical expression for the coherence estimate as a function of the direct-to-reverberant energy ratio is extended to several primary sources.
A comparison of community structure from the southeastern and central Bering Sea shelf: insights gained from acoustic backscatter
Authors: Miksis-Olds Jennifer L. , Denes Samuel L. , Warren Joseph D.
Published: April 2012

A two year time series of acoustic backscatter was acquired from the Middle Domain of the southeastern and central Bering Sea shelf starting in 2009. A three-frequency echosounder system was integrated into NOAA oceanographic moorings at these locations and provided information for the classification of backscatter into 4 biological categories: small (1-5mm), medium (5-15mm), and large (15-30mm) crustaceans, and resonant scatters. The seasonal pattern of backscatter intensity was tightly coupled to sea ice dynamics at both mooring sites, but the community structure and timing of zooplankton blooms differed between sites. Winter 2009 was a light ice year on the southeastern shelf compared to heavy ice presence in 2010. Comparison of backscatter intensity and structure between years at this location provides information about how sea ice extent impacts upper trophic level dynamics. Insights gained on the relationship between ice and community structure through analysis of acoustic backscatter between these two sites provides important information for predicting the ecosystem response in this area to variable and potentially decreasing seasonal ice extent associated with global climate change. [Work supported by ONR]
Effects of multiple scattering, attenuation, and dispersion in waveguide sensing of fish
Authors: Ratilal Purnima , Andrews Mark , Gong Zheng
Published: April 2012

An ocean acoustic waveguide remote sensing system can instantaneously image and continuously monitor fish populations distributed over continental shelf-scale regions. Here it is shown theoretically that the areal population density of fish groups can be estimated from their incoherently averaged broadband matched filtered scattered intensities measured using a waveguide remote sensing system with less than 10% error. A numerical Monte-Carlo model is developed to determine the statistical moments of the scattered returns from a fish group. It uses the parabolic equation to simulate acoustic field propagation in a random range-dependent ocean waveguide. The effects of (1) multiple scattering, (2) attenuation due to scattering, and (3) modal dispersion on fish population density imaging are examined. The model is applied to investigate population density imaging of shoaling Atlantic herring during the 2006 Gulf of Maine Experiment. Multiple scattering, attenuation and dispersion are found to be negligible at the imaging frequencies employed and for the herring densities observed. Coherent multiple scattering effects, such as resonance shifts, which can be significant for small highly dense fish groups on the order of the acoustic wavelength, are found to be negligible for the much larger groups typically imaged with a waveguide remote sensing system.
Prediction of acoustic properties of juvenile salmon, Oncorhynchus keta, for acoustic monitoring
Authors: Sawada Kouichi , Kurokawa Tadahide , Hashiba Akihiko
Published: April 2012

To monitor the juvenile salmons ( Oncorhynchus keta) swimming near surface, ventral aspect target strength (TS) of juvenile salmons were predicted by the prolate spheroid modal series model (PSMM). Soft X-rayimages of juvenile salmons (34.0-75.7 mm, in standard length, n=46) were taken from lateral and dorsal sides. The outlines of the swimbladders were digitized. TS pattern, which is a function of tilt angle, was calculated based on the morphological parameters of swimbladder and was averaged by assumed tilt-angle distributions. Normal distributions with nine different mean values (-20° – +20° at 5° step) and a constant s.d. of 20° were selected for mean TS calculations. The mean ratio of swimbladder height and the width was almost unity (s.d. 0.16). The maximum difference of the predicted mean TS by the difference of tilt-angle distributions became 1.4 dB, 2.3 dB, and 3.1 dB at 38 kHz, 70 kHz, 120 kHz, and 200 kHz, respectively. Using the model, TS=20logL-b, yielded TS=20logL-65.4 at 70 kHz, when a normal distribution with mean 0° and s.d. 20° was assumed.
A dual-modality system for imaging anatomy and vasculature in live mouse embryos
Authors: Chitnis Parag V. , Aristizábal Orlando , Sampathkumar Ashwin , Filoux Erwan , Mamou Jonathan , Turnbull Daniel H. , Ketterling Jeffrey A.
Published: April 2012

An imaging system that combined high-frequency ultrasound (HFU) with photoacoustics (PA) for in vivo visualization of anatomical and vascular maps in transgenic mouse embryos is presented. The system consisted of a five-element, 40-MHz, poly-vinylidenefluoride-co-trifluoroethylene (PVDF-TrFE) annular array with a hole in the center to facilitate coaxial delivery of light produced by a 532-nm pulsed laser. A phosphate buffer-filled petri-dish with a central hole was placed on the abdomen of an anesthetized mouse and a laparotomy was performed to expose an intact uterus. The probe was raster scanned to achieve 3-D imaging. The central element of the array was excited with a high-voltage impulse synchronized with the light pulse. The resulting ultrasound echo and PA signal from each scan location were digitized from all five array channels and synthetically focused in post-processing. The embryonic vasculature depicted by the PA image was co-registered with anatomical features represented in the HFU image. The head and the abdomen of embryos were imaged; feasibility of real-time, spatially co-registered, dual-modality in vivo imaging of mouse embryos was demonstrated.
Comparison of conventional multiple line acquisition with plane wave and diverging wave imaging for cardiac applications: a simulation study
Authors: Tong Ling , Gao Hang , Choi Hon Fai , D'hooge Jan
Published: April 2012

When imaging the heart, multiple line acquisition (MLA) is commonly used to increase the frame rate. For a typical phased array, frame rate can be increased by a factor of 4 using 4MLA with a less focused transmit beam. Alternatively, plane wave or diverging wave could be used allowing for 16MLA. However, transmit compounding is required in order to keep the spatial resolution acceptable resulting in a gain in frame rate similar to the one of a 4MLA system. The aim of this study was therefore to directly contrast the performance of a conventional 4MLA system to a plane wave and diverging wave imaging system by computer simulation. The performance of different imaging systems were investigated by quantitatively evaluating the characteristics of their two-way beams (i.e. -6dB beam width, side lobes to main lobe energy ratio, main lobe centralization and side lobes asymmetry). The results showed that the conventional 4MLA and plane wave imaging were very competitive imaging strategies while operating at a similar frame rate. 4MLA outperformed in the near field (i.e. 10mm-50mm), while plane wave imaging had better beam profiles in the far field (i.e. 50mm-90mm). The optimal settings of the diverging wave imaging system requires further study.
Accuracy of kidney stone size in conventional ultrasound Bmode imaging
Authors: Dunmire Barbrina , Sorensen Mathew , Kucewicz John , Bailey Michael , Cunitz Bryan , Harper Jonathan , Sapozhnikov Oleg , Crum Lawrence
Published: April 2012

The objective of this study was to determine the accuracy of conventional ultrasound imaging in sizing kidney stones, since this can be a determining factor in the treatment protocol for fragments on the order of 5 mm. Ex-vivo human kidney stones 3 to 12 mm were imaged in a water bath at depths from 6 to 10 cm using a Philips HDI5000 and Versonics software-based ultrasound system with the C4-2 transducer. Stone sizes were estimated offline a) manually by a sonographer and b) through an automated contrast based edge detection algorithm. Stone size was consistently overestimated with both instruments and by both estimation methods. On average, size was overestimated by 1 to 2 mm for stones 6 cm deep, and the overestimation increased with increasing depth and system gain. The overestimation was independent of actual stone size. These results suggest there is an inherent error in conventional ultrasound that leads to overestimation of stone size. These results also validate the software-based instrument for future work toward 1) investigating the sources of overestimation and 2) testing new methods for improving the accuracy of size estimation. Work supported by NIH DK43881 and DK092197, and NSBRI through NASA NCC 9-58.
Sub-surface elastography based on the dynamic shear strain analysis
Authors: Teramoto Kenbu , Hasan Mahbub
Published: April 2012

Quantitative acoustical imaging methods estimate the characteristics of the tissue elasticity of a region of interest having somewhat inhomogeneity contrasted to the surrounding soft tissues. The aim of this research is to propose a novel near-field imaging method for the shear wave elastography and sub-wavelength imaging. The proposed imaging methodology utilizes the determinant of a covariance matrix which is composed of the orthogonal pair of the shear strain variations. The image reconstruction theory can be summarized as follows. 1) The distributions of the normal displacement of the skin surface is governed by the 2-dimensional wave equation in the Lamb-wave field. 2) When the single propagating wave front exists on the surface of the tissue without any stiffer regions, therefore, the orthogonal pair of the out-of-surface shear strains are linearly dependent each other. Therefore the determinant of a covariance matrix which is composed of the orthogonal pair of the shear strains becomes zero. 3) When a region of interest having somewhat inhomogeneity exists, scattered wave field arises in the Lamb-wave field. Consequently, the determinant becomes larger than zero because of the independency between the orthogonal pair over the region of the scattered and incident wave field.
Performance optimization of acoustic concentrator
Authors: Wang Yu-ran , Zhang Hui , Zhang Shu-yi
Published: April 2012

Acoustic concentrator, focusing acoustic field and enhancing acoustic energy in a region, is presented. The concentrating performances and the scattering properties of the acoustic concentrator with multilayered alternative homogeneous materials at different frequencies are investigated by the frequency response analysis with finite-element method (FEM). The calculation results show that it has an optimized relation between the acoustic concentrating performances in the inner region and the scattering properties in the outer region of these concentrators. A kind of acoustic concentrators constructed by an array of cylindrical rigid scatterers in fluid is proposed. The multiple scattering theory (MST) is introduced to describe the superposition of the external incident acoustic field and the radiative scattered field induced by the array, by which the structure of the array and the performance of acoustic concentrator can be optimized. By the way, the MST can be used to estimate and optimize not only the acoustic concentrators but also other potential acoustic metamaterials. Acknowledgment: This work is supported by National Natural Science Foundation of China (No. 11004099 and 11174142), State Key Laboratory of Acoustics of Chinese Academy of Sciences, and also PAPD of Jiangsu Higher Education Institutions.
Theory of sound propagation in porous media allowing for spatial dispersion
Authors: Nemati Navid , Lafarge Denis , Duclos Aroune
Published: April 2012

We present here a new nonlocal theory of long-wavelength sound propagation in rigid-framed porous media saturated with a viscothermal fluid. For unbounded macroscopically homogeneous media, isotropic or having a preferred wave-guide axis; the symmetry of the problem suggests that the wave propagation should be described in terms of an Equivalent-fluid having frequency- and wavenumber-dependent density and bulk modulus. Based on considerations borrowed from electromagnetic theory, a definite procedure is proposed to compute these two quantities from microstructure. Using the finite element method to implement the computation procedure, the possible relevance of the new theory is tested in two simple types of 2D geometries: that of the so-called ultrasonic metamaterials made of an array of Helmholtz resonators, and that of an array of cylindrical circular solid inclusions.
The blended approach for teaching architectural acoustics—a preliminary study
Authors: Tang S. K. , Kam Roy
Published: April 2012

Teaching architectural acoustics in tertiary education is always a challenge not only because the acoustical effects are invisible but because these effects could be difficult to experience. This paper reports a preliminary study of exploring the blended approach that combines traditional classroom deliveries with online resources for teaching this topic in a Hong Kong university. The online resources of the proposed blended approach comprise (i) measurement of binaural pulse decays at many locations inside the university's auditorium; (ii) selected examples of pulse decays at locations of considerably difference in acoustical properties (RT, Clarity, etc.); and (iii) the mix between the decays and different music for demonstrating the influences of acoustical properties. Apart from traditional classroom deliveries, the students are free to experience the online resources as many times as they want and to reinforce their understanding of acoustical effects after class. The students' evaluation was generally positive about the proposed blended approach, with over 90% of them particularly indicating that the online resources (i) helped them understand the principles of architectural acoustics; (ii) have strengthened their learning skills in approaching the topic; (iii) helped them better relate the concepts learnt in class, and (iv) stimulated their interests in the topic.
Purpose of the international consortium on noise issues in emerging and developing countries
Authors: Finegold Lawrence , Schwela Dieter
Published: April 2012

As part of the growing interest in developing appropriate concepts and approaches for a “Global Noise Policy”, consideration needs to be given to how effective and affordable noise policies might need to vary based on factors which differ depending on the “state of development” of individual countries. Although there is no standard manner to distinguish between “developed”, “developing” and “emerging” countries, it is obvious that countries do differ in terms of their level of technological development, their financial capabilities and the availability of other resources required for adequate management of community noise. They also differ in their level of knowledge about the effects of noise, their views about the proper role of national and local governments, and the availability of engineering techniques to control exposure to community and occupational noise. This paper describes the current International Consortium on Noise Issues in Developing and Emerging Countries as a forum to facilitate discussions and share relevant information among the Consortium participants and other interested acoustics professionals.
Some challenges in developing community noise policy
Authors: Burgess Marion
Published: April 2012

There are a number of measures of success for environmental noise policy. For the regulatory or enforcement agency the measure of success is the lack of (or the reduction in) complaints about the noise in the area. This is a clearly quantifiable measure. For those responsible for the source of the noise a successful environmental policy is one that has clear and specific criteria for compliance which can be met in a cost effective manner. Again this is a quantifiable assessment. For the community the measure of success is satisfaction with the aural environment. Such satisfaction is a subjective measure. When establishing a noise policy the regulatory agency must match an understanding and knowledge of the community expectations with a quantifiable measure of noise. This measure then becomes the basis for the implementation of amelioration measures for the noise generator as well as the mechanism for the enforcement agency to verify compliance. Measuring the noise levels in the community has become relatively easy with modern instrumentation. Establishing the appropriate criteria remain the major challenges and will be discussed in this paper.
Brief review of legal framework on environmental noise in Japan
Authors: Yamada Ichiro
Published: April 2012

This paper makes a brief review of legal framework for the assessment of environmental noise in Japan and discusses issues of noise policy to be improved and needs to change or modify noise evaluation methods. For example, road traffic noise and aircraft noise are now evaluated using Leq metrics, but high speed railway noise is still evaluated using LASmax. It may cause a difficulty when evaluating the impact of compound noise exposure due to simultaneous road and railway traffic. On the other, level magnitude and frequency of C-weighted sound levels of noise events are still used as metrics for assessment and improvement of sound environment at public buildings such as schools, hospitals and so on near airfields and maneuvering grounds. Needs and requirements for sound environment may have greatly changed with the times. The author looks back over the way to use such metrics.
Sound production in Asian free reed mouth organs
Authors: Cottingham James P.
Published: April 2012

The Asian free reed wind instruments typically employ a free reed strongly coupled to a pipe resonator. In these reed-pipes the same reed often operates on both directions of airflow and behaves as a blown-open or outward striking reed, with playing frequency above both the resonant frequency of the pipe and the natural frequency of the reed. The Asian instruments were known in Europe when the Western free reed instruments were developed about 200 years ago, but in the European instruments a free reed of fundamentally different design was used. This paper summarizes the important acoustical properties of the Asian free reed mouth organs, contrasting them with the free reed instruments of European origin. Instruments considered include the khaen and other free reed mouth organs with multiple pipes as well as instruments consisting of a single free reed pipe in which the effective acoustical length is varied by the use of tone holes. Acoustical measurements made on these instruments include studies of reed vibration and impedance measurements of the pipes, with particular attention to the coupling of the reed vibration with the pipe resonator.