bluuebunny/crossref_metadata_2025 huggingface dataset:
Spherical microphone array processing of room impulse response data using frequency smoothing and singular-value decomposition
Authors: Huleihel Nejem , Rafaely Boaz
Published: April 2012

Room impulse responses (RIRs) play an important role in acoustical signal processing and room acoustics analysis. The problem of estimating the directions-of-arrival (DOA) of a source in a room and its reflections using RIR data and microphone arrays, is considered. Optimal array processing methods proposed for sound field analysis using spherical microphone array are utilized. Because of the possible coherence between the signals, these methods cannot be used directly, and a preprocessing technique is typically needed. Recently, frequency smoothing (FS) as a preprocessing technique has been developed for spherical microphone arrays. Although FS has already been developed for the general case, the study of its performance in a comprehensive manner, for spherical microphone arrays with RIR data has not been previously presented. Therefore, theoretical analysis of the signal matrix structure using RIR data is performed. The conclusions from this analysis may lead to an optimization of the smoothing process. A method for an optimal selection of frequencies in the smoothing process for the case of one reflection is presented, followed by formulations for smoothing in the more general case. Finally, FS and its relation to SVD of the array data matrix are also presented and discussed.
Joint spherical beam forming for directional analysis of reflections in rooms
Authors: Morgenstern Hai , Zotter Franz , Rafaely Boaz
Published: April 2012

This contribution presents a new approach for analyzing spatial directions in room impulse responses captured with source and receiver of adjustable directivity. A distinct peak in a room impulse response is usually associated with an acoustic path length of direct or reflected sound. Given the ability to modify the directivity of source and receiver by spherical beamforming, beam coefficients can be adjusted as to emphasize the peak at a preselected time instant. We present a new approach to jointly optimize the coefficients for both source and receiver under the constraint of a unit peak amplitude while minimizing the energy of the response. The beam pattern described by these coefficients highlights the dominant acoustic path directions of the corresponding path length at the source and the receiver.
On the Influence of sampling errors on the perception of spatial sound fields using spherical microphone arrays for auralization
Authors: Nowak Johannes
Published: April 2012

Spherical microphone distributions allow a three dimensional sampling of the sound field in a room. These microphone array data can be used for auralization on various playback systems. The aim of auralization is the reproduction of the sampled spatial sound field in order to give the listener the impression of being in the measured room. Due to the discrete spatial sampling process spatial aliasing corrupts the measured data. Therefore the resulting auralization quality is affected in terms of its spatial characteristics. Subjective quality measures for the spaciousness of sound fields can be represented by source localization accuracy, the apparent source width (ASW) and the listener envelopment (LEV). These subjective features are strongly related to objective measures like interaural level and time differences (ILD and ITD) or the interaural cross correlation (IACC). In subjective listening tests the influence of sampling errors on the binaural reproduction of a sampled sound field is investigated. The results are correlated with ITD, ILD and with IACC in order to gain an objective quality measure for sound fields recorded wtih spherical microphone arrays. The investigations are based on real measurement data taking various directions of arrival and different rooms into account.
Analysis and synthesis of room transfer function over a region of space using distributed spherical microphone arrays
Authors: Abhayapala Thushara , Samarasinghe Prasanga
Published: April 2012

Spatial sound field recording and reproduction in reverberant rooms requires measurement of room transfer functions (RTF) and corresponding compensation such as room equalization to avoid unintended effects. Typically, RTF rapidly varies over the room and hence requires a large number of point to point measurements to characterize the room. This paper uses (i) an efficient parameterization of the acoustic transfer function over a region of space, first introduced by Betlehem etal [“Theory and design of soundfield reproduction in reverberant rooms,” Journal of the Acoustic Society of America, Vol. 117, Issue 4, 2005] and (ii) a method to merge spatial soundfield recorded by distributed higher order microphones (such as spherical arrays) to analyze and synthesize the room transfer function over a region of space. This method provides a practical way to measure room transfer function over large areas with a minimum number of measurements.
Acousto-optic monitoring of high-intensity focused ultrasound lesion formation with fibre-coupled autocorrelation detection
Authors: Powell Samuel , Leung Terence S.
Published: April 2012

A focused acoustic source insonifies an optically turbid medium. Under coherent illumination the optical field in the focal region of the acoustic source is phase modulated by the acousto-optic interaction. The degree of this modulation can be determined using a fibre-coupled optical autocorrelation technique. Exploiting both the contrast of biological tissues at near-infrared wavelengths, and the non-linearity of the phase modulation process, it may be possible to determine the pertinent optical properties of biological tissues with a spatial resolution comparable to the dimensions of the acoustic focus. The same acoustic source may be employed therapeutically at higher power levels to instigate thermal necrosis and associated optical changes in e.g., tumours of the prostate. Whilst the proposed detection regime has significant technical and practical advantages over alternative approaches currently under investigation, it is incompatible with such treatment power levels. We present the theory of an interleaved treatment and sensing technique which could allow the use of our inherently compact and robust detection mechanism during HIFU therapy, simulated results obtained using a novel highly-parallel Monte-Carlo simulation code, and initial experimental results from the formation of lesions within ex vivo chicken breast samples.
Generating uniform lesions in high intensity focused ultrasound ablation
Authors: Zhou Yufeng
Published: April 2012

High intensity focused ultrasound (HIFU) is emerging as an effective oncology treatment modality. Because of thermal diffusion from nearby spots, the lesion size will gradually become larger as HIFU progresses. However, uniform lesions with the least energy exposure are preferred by the physician in tumor ablation. In this study, an algorithm was developed to determine the number of pulses delivered to each spot in order to generate uniform lesion pattern that fills the region-of-interest completely using different scanning pathways (raster scanning, spiral scanning from the center to the outside and from the outside to the center), spot spacing, and motion time. It is found that spiral scanning from the outside to the center with spot spacing of 2 mm and motion time less than 10 s would need the least number of pulses in uniform lesion production with the minimal temperature elevation. In addition, the effects of thermal properties of tissue (i.e., specific heat capacity, convective heat transfer coefficient, and thermal conductivity) on HIFU ablation were investigated. Altogether, dynamically adjusting ultrasound exposure energy can improve the efficacy and safety of HIFU ablation, and the treatment planning depends on the scanning protocol and thermal properties of the target.
Infrared and hydrophone system for eastimating the output power of high intensity focused ultrasound transducer
Authors: Yu Ying , Shen Guofeng , Bai Jingfeng , Chen Yazhu
Published: April 2012

Output power of high intensity focused ultrasound (HIFU) transducer is not only important for the safety and efficiency of clinical treatment, but also for therapy planning in medical applications. In the current paper, a method was proposed to estimate output power of HIFU using a hydrophone and infrared system. The proposed method is independent of the thermal and acoustic parameters of the acoustic absorber and the type of transducer that has been measured. This method consisted of five steps. The amplitude absorption coefficient of the medium was measured through the first two steps. Through the second and third steps, we estimated the ratio of the heat capacity per unit volume to the ultrasonic amplitude absorption coefficient of the absorber. In fourth step, the temperature change at the absorber/air was captured by an IR camera, and the temperature change rate (TCR) was used to estimate the intensity based on the parameters measured by the first three steps. In last step, the sound power of HIFU transducer at high driving voltage can be obtained following the relationship between the sound intensity and sound power. The method was proposed and simulated in three 2-D 1.36 MHz-phased arrays and two kinds of absorbers. In last step, the sound power of HIFU transducer at high driving voltage can be obtained following the relationship between the sound intensity and sound power.
Transversal modes and acoustic attenuation characteristics of rectangular and oval silencers with perforated tube
Authors: Fang Zhi , Ji Zhenlin
Published: April 2012

As the analytical method is not suitable for the silencers with arbitrary cross-sectional shape, the finite element method is developed to calculate the transversal modes of rectangular and oval silencers with circular perforated tube, the corresponding finite element formulation is derived and the computational code is written. In order to validate the present finite element formulation and computational code, the transversal modal frequencies of circular concentric straight-through perforated tube silencer are evaluated analytically and compared with the finite element results, and good agreements between them are observed. Then, the finite element method is used to investigate the effects of hole diameter, porosity and tube offset on the transversal modes and acoustic attenuation characteristics of rectangular and oval silencers with circular perforated tube. The numerical results demonstrate that, smaller hole diameter or higher porosity leads to higher plane wave cut-off frequencies and better acoustic attenuation in the middle frequency range, and the hole diameter and porosity have negligible effect on the plane wave cut-off frequencies when the porosity is higher than 40%. The plane wave cut-off frequencies of the non-coaxial silencers are lower than the concentric configurations in general.
Narrow sidebranches for duct silencing
Authors: Tang S.K.
Published: April 2012

A narrow sidebranch attached to the rigid wall of a duct will result in high sound transmission loss across it at its resonance frequencies. Coupling narrow sidebranches together will therefore produce a broadband silencing device for duct noise control. However, the sidebranch length variation will affect the broadband performance. Numerical investigation was carried out in this study to understand the effects of the sidebranch length variation and the sidebranch width on the overall sound attenuation spectrum of the coupled sidebranches. It is found that broadband sound attenuation below the first higher mode cut-off frequency of the main duct of over 20dB across the working bandwidth can be achieved if the length variation and widths of the sidebranches are appropriately chosen.
Investigating physical parameters associated with listeners' perceived auditory depth
Authors: Kim Sungyoung , Okumura Hiraku , Otani Makoto
Published: April 2012

Recent 3D technologies allow viewers to perceive disparities in the depths of visual objects and to thus experience more realistic visual information. As for 3D auditory display, however, conventional loudspeaker layouts have not managed to manipulate perceived auditory depth in a sufficiently convincing way. Previously, we proposed a new method that utilizes a prototype electrostatic loudspeaker that is located above the listening position and generates auditory images similar to those of headphones. Using this phenomenon and amplitude-based panning, we were able to move auditory images along the line connecting the front loudspeaker and the listening position. In this study, we investigated physical factors that were idiosyncratic in electrostatic loudspeaker reproduction and that caused listeners to perceive sounds as being nearby. We both measured and simulated the loudspeaker-to-ear transfer functions using various types of loudspeakers at multiple locations, and extracted several physical parameters, including the InterAural Phase Difference (IAPD) and the InterAural Level Difference (IALD). The result revealed a new physical quantity that was associated with loudspeaker-listener distance: variance in phase response differentials. We conclude that the electrostatic loudspeaker produced relatively less variance in phase response differentials and allowed listeners to perceive near auditory images as if listening to headphones and to enjoy better integrated 3D content.
Role of 4 - 8 kHz band component for wideband noise localization in median plane
Authors: Iwaya Yukio , Magariyachi Tetsu , Otani Makoto , Suzuki Yôiti
Published: April 2012

When we localize a sound image, interaural cues, such as interaural level differences and interaural time/phase differences, are used in horizontal plane. On the other hand in median plane localization, spectral cues are more important than that of interaural cues. However, concrete spectral cues involved in head-related transfer functions are not sufficiently investigated. To clarify spectral cues of sound localization in a median plane, we conducted a sound localization test with broadband noises with frequency spectrum manipulation. The noises were generated based on a pink noise and modified so that they had various 1 oct. band levels (-6, -3, 0, +3, and +6 dB) in 4-8 kHz band. The noises were radiated via two loudspeakers located at 30 and 60 degrees of elevations, respectively, in the median plane. Nevertheless, the perceived elevation was shifted according to the band levels. The changes of perceived elevation resembled those of relative power levels in head-related transfer functions. This suggests that the relative level of this band in the head-related transfer functions would be one of spectral cues for elevation perception.
Noise source identification with increased spatial resolution used in automotive industry
Authors: Gade Svend , Hald Jørgen
Published: April 2012

Delay and sum Planar Beamforming has been a widely used Noise Source Identification Technique for the last decade. It is a quick one shot measurement technique being able to map sources that are larger than the array itself. The spatial resolution is proportional to distance between array and source and inversely proportional to wavelength, thus the resolution is only good a medium to high frequencies. Improved algorithms using iterative de-convolution techniques offers up to three times better resolution. The principle behind these techniques is described in this paper, as well as measurement examples from the automotive industry are presented.
A large scale study of the health effects of transportation noise in Hong Kong
Authors: Lam Kin-che , Brown A. Lex , Kamp I van , Wong TW , Chan YK , Yeung MKL , Lui A , Law CW , Chung YT
Published: April 2012

Transportation noise is a problem in many large cities with possible annoyance and health related consequences. To provide the necessary data for making informed decisions on noise control strategies, a large scale study was commissioned by the Environmental Protection Department of the Hong Kong SAR Government and undertaken by an international team coordinated by the Chinese University of Hong Kong in 2009-2010. The study was based on the interview of a total of 10,077 randomly selected households and a city-wide assessment of the exposure of the selected households to road traffic noise using the state-of-the-art noise mapping technique. Noise response was measured by an internationally standardised question on an 11-point numeric scale (ISO/TS 15666, 2003). It was very much the first ever comprehensive study of such a scale, following strict international standards, carried out in Asian countries. This paper describes rationale of the study, key research questions, sampling and questionnaire design, data validation and quality control and the overall study methodology. The key study findings are given for possible comparison with similar large scale studies. Implications for noise control based on such findings will also be discussed.
International comparison of Hong Kong response to road traffic noise
Authors: Brown A.L. , Lam KC , Kamp I van , Chan YK , Lui A
Published: April 2012

The association between transport related noise and community response to that of exposure has been well documented. In order to develop a baseline data set for Hong Kong and enable international comparison, a household survey was conducted territory-wide in 2009-2010. The response rate was high of 75% and a total of 10,077 households were interviewed. Noise response was measured by an internationally standardised question on an 11-point numeric scale (ISO/TS 15666, 2003). Transformations were made to the data by means of the “Miedema approach” to allow for comparisons. Estimates of the percentages of highly annoyed (%HA) at the population level were plotted against Lden and compared with both Miedema's generalized curve derived from international data sets and those produced by Phan (2008) based on Vietnamese data. The Hong Kong curve lay considerably below that of Miedema, but was comparable with Phan's curves. Personal and contextual factors related to response were: noise sensitivity, window closing and home ownership. Factors reducing annoyance were: access to a quiet room in the dwelling, satisfaction with environmental circumstances in the immediate residential area and the number of households in the living quarters. These findings are well in line with those elsewhere.
A new approach to investigate annoyance responses to sound elements
Authors: Hume Ken
Published: April 2012

Soundscape research indicates that sound perception is a complex auditory experience with emotional content and the potential for annoyance should not be measured simply in terms of loudness. However, there are limited objective tools available to investigate annoyance and the relative health implications of negative soundscape elements. As part of a Positive Soundscapes (UK) project, the physiological responses [heart rate (HR), respiratory rate (RR) and electromyography (EMG) ] to soundscape elements were compared with the subjective assessment of pleasantness and arousal (assessed on 9 point scales) evoked in 80 subjects who listened to 18 x 8 second sound-clips. The data were analyzed via a linear mixed-model ANOVA. Listening to sound-clips lowered HR slightly but significantly. More unpleasant sound-clips caused larger falls in HR. Listening to a sound-clip raised RR slightly but significantly. The more pleasant the sound-clip was judged the greater was the rise in RR. The EMG tended to be raised by unpleasant sound-clips. Therefore, distinctive significant relationships were found between physiological measurements and the subjective estimates of pleasantness for the sound-clips presented. Therefore, an objective technique could be developed for sound engineering which allows for the potential investigation and assessment of annoyance levels to various sound elements.
Development of long-term data acquisition system of noise exposure and personal behavior for analysis of health risk: Research background
Authors: Imaizumi Hiroyuki , Fujimoto Kazutoshi , Anai Ken , Hiraguri Yasuhiro
Published: April 2012

Since people living in urban areas are continuously exposed to loud environmental noises for a long duration, the noise has to be treated not only as nuisance in our daily lives and adverse psychological effect but also as possible risk on health. WHO has presented an environmental noise guideline and has suggested dangers or risks on health by long-term high noise exposure, and has recently published nighttime noise guideline to prevent adverse health effect to sleep disturbance. Some research projects in EU have revealed that detailed measurement in time of individual noise exposure is needed to improve the current assessment method, instead of those based on energy-averaged value over the exposed duration to noise. It suggests necessity of short time-interval measurement of individual noise exposure as well as information when and where people are exposed to the noise. It is also necessary to measure environmental condition in nightitme, since the condition very likely disturbs our sleep and therefore gives some effects to our health. From these circumstances and relating issues in Japanese, we have established a new research project which aims to investigate the effect of individual noise exposure on health. This report presents the research background and objectives.
Long term noise performance of road surfaces in urban environment
Authors: Lam YK , Ng IWK , Hung WT
Published: April 2012

Noise reduction performance of road surfaces is of great concern as it has direct impact on the cost-effectiveness of this measure for noise abatement purpose. Over 70 low noise road surfaces, mainly polymer modified porous asphalts, were laid on low speed streets (speed limit < 50 km/h) in the urban areas of Hong Kong. A single-wheeled CPX trailer fitted with a local commonly fitted tyre, the yokohama tyre, was used to measure the tyre/road noise on eight sections of stone mastic asphalt surfaces for over one year and over twenty sections of polymer modified porous asphalt surfaces from one to three years. While the monitoring work is going on, initial results show that the tyre/road noise on stone mastic asphalt surfaces and that on polymer modified porous asphalt were different, and had different aging effect in noise terms.
Temperature effects on tyre/road noise on wearing course and stone mastic asphalt surfaces in Hong Kong
Authors: Hung W.T. , Lam Y.K. , Kam E.K.Y.
Published: April 2012

To assess the impact of temperature on tyre/road noise, two sets of tyre/road noise survey were conducted; one in the day time and the other in the night time. A twin-wheeled CPX trailer fitted Standard Road Testing Tyre (SRTT) was employed to measure the tyre/road noise. Four stone mastic asphalt and four wearing course surfaces which are common in Hong Kong were chosen for this study. The surveys were conducted in the late summer of Hong Kong in 2011. At least four runs were made on each road section in each set of the survey. It was found that the tyre/road noise is sensitive to both air and road surface temperatures on the four wearing course and four stone mastic asphalt surfaces. The SMA surfaces are more sensitive than WC surfaces. The air temperature coefficient ranges from -0.122 to -0.462 for the four WC surfaces and from -0.265 to -0.945 for the four SMA surfaces. The road temperature coefficient ranges from -0.030 to 0.086 for four WC surfaces and from -0.056 to -0.139 for SMA surfaces.
A Study on the acoustical properties of road surfaces of recycled CFB materials
Authors: Ngo Ha , Li Zhuang , Davis Alan
Published: April 2012

Traffic noise and noise control are major concerns of transportation, as noise and vibration will cause both psychological and physiological consequences. Great efforts have been made to use more sound absorbent road surfaces in order to reduce traffic noise. The raw materials under study are recycled byproducts from circulating fluidized bed boiler (CFB). The recycled CFB materials have been approved for use by the Environmental and Transportation Departments in various regions throughout the United States for road stabilization and base/surface installations. These (CFB) materials have shown good ecological, civil and mechanical properties, and are more environmentally friendly than asphalt and concrete. However, the acoustical properties of the pavements are not known. Two types of measurements have been conducted. First, the traffic noise was measured using the statistical pass-by method on various road surfaces and a comprehensive comparison was conducted. Second, the sound absorption coefficients of the CFB materials were measured using impedance tubes.
Differentiating the roles of parietal cortex, auditory cortex and the thalamus in auditory stream segregation
Authors: Cusack Rhodri
Published: April 2012

In the last decade, great progress has been made in identifying neural structures that underlie auditory streaming. Regions of the auditory cortex have been implicated in macaque electrophysiology (Fishman et al. 2001, 2004; Micheyl et al, 2005, 2007), human MEG (Gutschalk et al, 2005, 2007) and fMRI (Kondo & Kashino, 2009; Deike et al, 2010; Hill et al, 2011). The parietal cortex has been implicated using human fMRI (Hill et al, 2011; Cusack et al, 2005) and MEG (Teki et al, 2011). Finally, there is intriguing data from fMRI on the involvement of the thalamus (Kondo & Kashino, 2009), and from electrophysiology on subcortical regions in the auditory periphery (Pressnitzer et al, 2008). However, the roles of these different regions are far from clear. I will report results from multi-voxel pattern analyses of fMRI data, which probe what kind of information is encoded within each brain region. This revealed markers of stream segregation in the thalamus, auditory cortex and the parietal cortex, but representation of the basic stimulus features only in auditory cortex. I will discuss the roles of the different regions in automatic and voluntary scene analysis, selective attention, and multimodal object representation.
Concurrent sound perception interferes with signal detection
Authors: Alain Claude , Leung Ada
Published: April 2012

The object-based account of auditory scene analysis posits that attention operates on perceptual auditory objects. An important implication of such a theory is that perception of two simultaneous auditory objects may interfere with signal detection. In a series of experiments, we show that perception of concurrent sound objects, induced by varying frequency of one tonal component in an otherwise periodic sound complex, impaired gap detection. This effect was observed for a wide range of gap duration, and was greater when the mistuned harmonic was perceived as a separate object. These results suggest that one auditory object is processed at a time, which is consistent with the object-based theory. The impaired gap detection in the mistuned harmonic could be interpreted in terms of competition for attention between the gap and the mistuned harmonic: The perception of the mistuned harmonic as a separate object “wins” the competition for attentional resources.
Auditory scene analysis: It's all about expectations!
Authors: Elhilali Mounya
Published: April 2012

Cocktail parties and other complex acoustic scenes present organisms with intricate sound mixtures and configurations. Perception in these complex settings relies on tracking regularities over time of sound patterns that arise from a statistical parsing of the scene as well as priors and expectations that bias how we organize the scene into its putative sound objects. Predictions arising from these expectations and sound regularities operate differently along different acoustic and cognitive domains. Here, we discuss the role of the interplay of expectations along these different domains in mediating the organization of complex acoustic scenes.
Prosodic realization of focus in Mandarin by advanced American learners of Chinese
Authors: Chen Ying , Guion-Anderson Susan
Published: April 2012

Prosodic focus in Beijing Mandarin and American English involves language-specific patterns of expansion in duration, F0 and intensity on the focused item as well as post-focus compression (PFC) of F0 and intensity (Xu, 1999; Xu & Xu, 2005). The current study examined whether advanced American learners of Mandarin realize prosodic focus and PFC in the same way as native speakers. Ten native Beijing Mandarin speakers and ten non-Chinese American learners of Mandarin produced stimuli with four Mandarin tone types on focused constituents, and Tone 1 in pre-focus and post-focus constituents. Preliminary results indicated that the learners produced focus-related duration changes in a manner similar to native Mandarin speakers. However, learners did not show native-like patterns of in-focus changes in intensity on Tone 2, mean F0 on Tone 1, and F0 excursion on Tone 4. Furthermore, learners showed no PFC of F0 or intensity, consistent with the idea that PFC is not easily transferred from L1 to L2 (Wu & Chung, 2011). Future work will investigate prosodic focus in the Mandarin of Chinese-heritage American learners. The goal is to investigate whether earlier exposure to the language (via heritage) affects learners' ability to realize prosodic focus in a native-like manner.
Phonetic characteristics cuing continuation of talking beyond possible completion in Chinese conversation
Authors: Zhang Wei , Li Bin , Chan Angela
Published: April 2012

One of the grossly apparent facts about conversation is that speakers take turns to talk (Sacks, Schegloff & Jefferson 1974). Both syntactic and prosodic cues contribute to the smooth transition between conversational turns (Couper-Kuhlen & Ford 2004, Ford & Thompson 1996). Two prominent and similar turn-holding devices have been identified, namely, rush-through (Schegloff 1982, 1998) and latching (Liddicoat 2007), which enable speakers to bid for turn continuation beyond possible completion of a turn. However, systematic and detailed examination of their exact phonetic design has been reported only recently for the English data (Walker 2003, 2010). In this study, data from naturally-occurring Mandarin Chinese conversations have been examined for prosodic correlates which are associated with turn continuation. These correlates include pitch variation, intensity, and vowel duration. It is found that prosodic cues vary between the two turn-holding devices. The findings have also been compared with those reported for English conversations. This research contributes to cross-linguistic investigation of the prosody that constitutes turn-holding functions in conversation. Acknowledgement: This study is supported by the General Research Fund [CityU 151408] awarded by the Hong Kong Research Grants Council.
Robust voice activity detection based on harmonic to noise ratio
Authors: Guo Yanmeng , Fu Qiang
Published: April 2012

A robust voice activity detection algorithm based on harmonic to noise ratio (HNR) is proposed. Harmonic to noise ratio is high in voice segments, because most of the voice energy distributes on the harmonic structure. However, it is unreliable or complicated to estimate the harmonic frequencies of noisy speech, and the HNR in full frequency band is not robust for environments with non-stationary band-limited noise. In this paper, several harmonic templates with fundamental frequency changing in log-scale step are used to match the wide-band voice harmonic structure, and the fundamental frequencies are not need to be estimated. To avoid the non-stationary band-limited noise, the contaminated frequencies are neglected automatically by frequency bin selection, which discards the harmonic and the noisy bins with the highest and lowest energy to keep the main clear harmonic structure. The final voice activity detection is based on the HNR of continuous frames, and it shows robust performance on several databases.
Signal processing in underwater acoustic communication system for manned deep submersible “Jiaolong”
Authors: Zhu Weiqing , Zhu Min , Wu Yanbo , Yang Bo , Xu Lijun , Fu Xiang , Pan Feng
Published: April 2012

In this report, signal processing in underwater acoustic communication system for manned deep submersible “Jiaolong” is introduced. 1. Four communication methods are integrated to meet different needs: (1) coherent underwater acoustic communication, with a variable transmission rate from 5kbps to 15kbps, to transmit images. (2) Non-coherent underwater acoustic communication, with a transmission rate 300bps, to transmit texts, instructions, and sensor data. (3) Spread spectrum underwater acoustic communication, with a transmission rate 16bps, to transmit instructions. (4) Underwater voice communication, using analogy modulation method to transmit human voice. 2. Signal processing method in coherent communication mainly consists of concatenation of decision feedback equalizer and Turbo decoder, and wavelet based image compression with fixed length coding. In the equalizer, Doppler compensation, multichannel combining and equalizer coefficients updating are all using fast self-optimized adaptive algorithm. 3. A linear hydrophone array is lowered from the mother ship to certain depth, and spatial diversity combining technology is adopted. From July to August 2011, diving trial of “Jiaolong” was carried out in the Pacific Ocean. The communication distance can cover nearly all ocean depth. The covering conical area is wider than 100 degree. An optical/acoustic image could be transmitted in 7 or 14 seconds.
Orthogonal frequency-division multiplexing underwater acoustic communications with time reversal processing
Authors: Nie Xingyang , Xu Wen
Published: April 2012

In dispersive underwater channels where impulse responses commonly last tens of milliseconds, large symbol durations and guard intervals are needed for orthogonal frequency-division multiplexing (OFDM) acoustic communications, which could introduce severe inter-carrier interferences and reduces effective data rate. This paper presents a scheme of OFDM transmission combined with passive time reversal processing, which has been demonstrated as a promising self-adaptive technique to compensate for multipath distortion explicitly due to its spatial focusing and temporal compressing characteristics. Using time reversal as a preprocessing step prior to OFDM, the equivalent channel impulse response is greatly shortened; moderate symbol durations and guard intervals can thus be used the same way as in conventional OFDM schemes. Moreover, to improve the robustness in harsh-environment applications, Reed Solomon channel coding is exploited for its good performance against burst errors caused by channel fading and ambient burst noise. Tradeoffs between data rate and robustness are discussed along with the transmission scheme. Finally some field experimental results are presented, which demonstrate the effectiveness of the developed approach. [Work supported by Chinese 863 high-tech program under Grant 2009AA093601]
A dual-channel cross-layer architecture for underwater acoustic networks
Authors: Xu Xiaomei , Zou Zheguang , Tao Yi
Published: April 2012

The performance of underwater acoustic networks( UAN) is affected by the node device constraints of memory, processing power, battery life time and network topology variation. To improve the performance and to utilize scarce resource can be obtained with a Cross-layer design. Cross-layer design, one of the key technique in underwater communication networks, overcomes the disadvantages of the strictly layered networks such as nonoptimality and inflexibility. It enables the system to utilize the limited resources more sufficiently, especially in no central control, rapid changes topology of underwater networks, and achieves better performance. This paper discusses the benefits of cross-layer underwater acoustic networks and related work, introduces a representative cross-layer architecture, named dual-channel cross-layer architecture, to promote the overall system performance for underwater networks. In addition, three cross-layer solutions, node adaptive modulation and channel coding, joint design of MAC and nodes ranging, and MAC networks information extraction, are presented perfectly based on this architecture. Finally, by using NI compactRIO and LabVIEW, an experimental networking was carried out, which demonstrated promising resluts.
Inversion of sediment geoacoustic parameters with echo envelope characteristics
Authors: Li Guofu , Gao Dazhi , Wang Ning
Published: April 2012

Bottom backscattered signals of different sites located in the Bohai Sea of China were acquired using a calibrated vertically oriented echosounder working at 20kHz. Envelopes of the received signals are extracted. The backscattering intensity envelope is also computed based on a time-dependent model described by Daniel D.Sternlicht and Christian P.de Moustier, of all input parameters the mean grain size is used only. Other geoacoustic parameters related to the mean grain size are adapted from the APL-UW High-Frequency Ocean Environment Acoustics Models Handbook. Both the envelopes of experimental and modeled are used to calculate characteristics such as the duration of echoes, statistical and spectral moments and finally give out the estimation of mean grain sizes. The estimated parameters are consistent with the ground truth.
Assessment of geoacoustic inversion methods
Authors: Chapman Ross
Published: April 2012

Sound transmission in shallow water is strongly affected by the physical and acoustic properties of the ocean bottom. Over the past decade, sophisticated methods have been developed for estimating parameters of geoacoustic models that account for the interaction of sound with the bottom. The performance of the methods has been compared in benchmarking exercises for range-independent and range-dependent shallow water environments using simulated data. This paper extends the comparison of geoacoustic inversion methods to assess performance using data from experiments at sites where the ocean bottom environment was well known from independent ground truth information. There are several aspects to performance assessment. The comparison presented here shows the accuracy of estimates from various inversion methods compared to the ground truth data about the ocean bottom sediments. The methods that are compared include matched field inversion; perturbation techniques based on modal waveumber estimation; bottom loss measurements; travel time tomography; and in situ physical measurement. The assessment shows overall consistency from all the methods.
Improving orchestra pits for the benefit of musicians
Authors: Dance Stephen , Losasa Alba , Large Sarah , Walters Sheldon
Published: April 2012

Increased publicity regarding hearing loss in those working in the music and entertainment sectors and the need to meet compliance with the UK Control of Noise at Work Regulations 2005 has heightened the importance and need to reduce noise exposure of professional classical musicians. Advice on hearing protection for musicians often concludes that ear plugs are the most effective, although often problematic, noise mitigation measure and hence the need for alternative solutions. With the full co-operation of the Royal Academy of Music the noise exposure of musicians has been investigated to establish their typical noise dose. It was found that the orchestra pit was the most challenging environment, primarily limited by available space. To mitigate the noise dose of the musicians' two approaches were taken – changing the design of the pit and developing new zero footprint acoustic screens. The later involved developing a hybrid absorbing screen that could be place on music stands. The former involved detailed room acoustic measurements and acoustical computer simulation of the theatre. The solutions provided a measured and predicted reduction in noise level of between 5-8 dBA for all the musicians without affecting the musical perception of either the conductor or audience.
Nonlinear viscous stress modification in the lipid-coated contrast agent microbubble dynamic model
Authors: Li Qian , Tu Juan , Zhang Dong
Published: April 2012

In the existing shell models for lipid-encapsulated microbubbles, the viscous shell terms always have the linear form, which assumes that the viscous stresses acting inside the lipid shell are proportional to the shell shear rate with constant coefficient of proportionality. In the present work, a modified dynamic model is proposed for the lipid-coated ultrasound contrast agent (UCA) bubbles by taking into account the nonlinear viscous properties of a lipid monolayer coating. The dynamic responses of the UCA bubbles exposed to 1-MHz ultrasound pulses with varied driving pressures were measured using a modified flowcytometry system. By fitted the measured bubble dynamic curves with the proposed model, it has been verified that the use of the nonlinear theory for shell viscosity allows one to more accurately model the complicated UCA microbubble rheological properties.
Stable inertial cavitation with a confocal ultrasonic device for drug release from nongaseous sonosensitive liposomes
Authors: Lafon Cyril , Mestas Jean-Louis , Ngo Jacqueline , Somaglino Lucie , Mari Jean-Martial , Chesnais Sabrina , Nilssen Esben , Chapelon Jean-Yves
Published: April 2012

Encapsulating chemotherapeutic agents in liposomes improves targeting and efficacy of treatments against some tumors. The present work aims at evaluating if sonosensitive liposomes combined with cavitation for drug delivery enhance efficacy and reduce toxicity. Two focused beams were combined for stabilizing the cavitation cloud and an imaging probe used for guidance. Each 1MHz focused transducer had a 5cm diameter and focal length. Exposure conditions were 10.8kW/cm2 Isppa, 250Hz PRF and 1% duty cycle. Phosphatidylcholine-based nongaseous liposomes were loaded with Doxorubicin. To control for mechanical tissue damage, AT2 Dunning tumors on rats were first exposed to ultrasound only. Treatment induced temperature rose below 0.5° C. The tumor growth was not significantly slowed down by ultrasound, but histological examination of tumors evidenced large areas of necrosis which resorbed one week after ultrasound. The new liposomes were compared with conventional HSPC-based liposomes in terms of efficacy and toxicity on the same tumor model. Ultrasound led to equivalent efficacy when applied on HSPC-based liposomes, while the new liposomes were efficient only with concomitant cavitation. We present a confocal ultrasound set-up able to provide sufficient inertial cavitation for drug release from a nongaseous liposome with reduced systemic toxicity. Eureka-labelled project (E!4056) funded by NRC, FFN and OSEO.
Modeling the interaction of tandem bubbles for biomedical applications
Authors: Hay Todd A. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F. , Hsiao Chao-Tsung , Choi Jin-Keun , Singh Sowmitra , Chahine Georges L. , Sankin Georgy N. , Yuan Fang , Piech David , Zhong Pei
Published: April 2012

Recent experiments, motivated by ultrasound-mediated drug and gene delivery, have utilized laser-generated tandem microbubbles to produce directional and targeted membrane poration of individual cells in microfluidic systems [Sankin et al., Phys. Rev. Lett. 105, 078101 (2010)]. Two models describing the dynamics of coupled bubbles between parallel plates have been applied to understand these observations. The first approach is based on the Boundary Element Method in both 2D and 3D coordinate systems for bubbles bounded by finite rigid plates. Deformation of the bubble surfaces is taken into account, capturing phenomena such as bubble jetting and fragmentation [Hsiao et al., Ultrasound Med. Biol. 36, 2065-2079 (2010)]. The second approach is semi-analytic, accounts for fluid compressibility and elasticity of the plates, but is limited to spherical bubble pulsation [Hay et al., J. Acoust. Soc. Am. 129, 2477(A) (2011)]. Observations of tandem bubble interaction with adjacent biological cells and their potential for controlling cell poration will be discussed. Comparisons between simulation results obtained from the two models, as well as comparisons between the models and experimental measurements, will be presented. [Work supported by NIH grant nos. DK070618 and EB011603 (UT), 2R44EB005139-02A1 (DFI), DK052985 and RR016802 (Duke).]
A logging while drilling acoustic isolation technology by varying thickness of drill collars at a distance greater than wavelength
Authors: Su Yuanda , Tang Xiaoming , Tan Baohai , Qin Yukun
Published: April 2012

A key technology for logging while drilling (LWD) acoustic measurements is the design of an acoustic isolator to suppress tool waves propagating along the drill collar, such that acoustic signals from earth formations can be effectively measured under LWD conditions. Up to now, the LWD acoustic isolation is achieved by periodically cutting grooves along the drill collar between acoustic transmitter and receivers. Such a technique, although it is effective, reduces the mechanical strength of the drill collar and adds cost to the manufacturing and maintenance of the LWD tool, hindering the application of the LWD acoustic technology. We have developed an LWD acoustic technology that does not use the groove-cutting design. We utilize the inherent frequency stopband for extensional wave propagation along a cylindrical pipe and effectively broaden the stopband by combining drill pipes of different cross-section areas whose lengths are greater than a wavelength but are shorter than the transmitter-to-receiver distance. After propagation through the combined drill collar system, the stopband in the collar extensional wave is significantly widened and the wave amplitude in the stopband is substantially reduced. Making LWD acoustic measurements in this widened stopband allows for recording acoustic signals from the surrounding formation.
Automatic drowsiness detection system using autoregressive coefficients and neural network
Authors: Han Hyungseob , Kim Dajung , Chong Uipil
Published: April 2012

One of the main reasons for serious road accidents is driving while drowsy. For this reason, drowsiness detection and warning system for drivers has recently become a very important issue. Monitoring physiological signals provides the possibility of detecting features of drowsiness and fatigue of drivers. One of the effective signals is to measure electroencephalogram (EEG) signals. The aim of this study is to extract drowsiness-related features from a set of EEG signals and to classify the features into three states: alertness, drowsiness, sleepiness. This paper proposes a neural-network-based drowsiness detection system using Autoregressive (AR) coefficients as feature vectors and Multi-Layer Perceptron (MLP) as a classifier. Specifically, the proposed method estimates AR coefficients using EIV (Errors-In Variables) providing an accurate estimation in a noisy process and linear predictive coding (LPC) analysis not considering noise. Samples of EEG data from each predefined state were used to train the MLP program by using the proposed feature extraction algorithms. The trained MLP program was tested on unclassified EEG data and subsequently reviewed according to manual classification.