bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of two acoustic continua on the within-category perceptual structure of tones
Authors: Wu Junru
Published: April 2012

The present study investigated effects of two acoustic continua on the within-category perceptual structure of Putonghua Tone 2 and Tone 3. These two tones were simulated with tokens varying along two acoustic continua about F0 contour: the timing of F0 turning point and falling of F0. Three different syllable durations were tested with voice quality under control. Multidimensional scaling analyses were applied to investigate relative influence of phonetic identification and category goodness on the perceptual dissimilarity of synthesized tonal tokens. The result revealed that Tone 3 has later F0 turning point and greater F0 falling than Tone 2, which confirms former findings. The new finding is that perceptual representation of these two tones categories is different in their internal structures. Best tokens disperse within categories and are usually not unique. Perceptual space involving Tone 2 tokens shrink but that involving Tone 3 doesn't. Goodness rating contributes significantly to the dissimilarity scaling across Tone 2 tokens but not Tone 3 tokens.
How is a five-level-tone contrast possible?
Authors: Kuang Jianjing
Published: April 2012

Black Miao is the most famous five-level-tone language (reported in Kwan1966), which has been a challenge for tonal theories; however, the phonetic realizations of these five level tones have not been studied. This study thus examines the same Black Miao dialect as the one Fang-Kuei Li recorded. We conducted both production and perception experiments in the field to understand how this five-level-tone contrast is possible. Simultaneous EGG and acoustic recordings were made in the production experiment; the perception experiment consisted of an identification task and a discrimination task. Preliminary results show that these five level tones do not merely contrast in F0; non-modal phonations play an important role in the tonal contrasts. Vocal fry and tense voice help distinguish 11 and 55 from other tones, while breathy phonation distinguishes 33 from 22 and 44. Therefore, the tonal contrasts are optimal in dispersion in a 2-D (F0 and phonation) tone space.
Acoustic privacy area generation based on simple summation of numerous loudspeaker signals
Authors: Okamoto Takuma , Iwaya Yukio , Suzuki Yo-iti
Published: April 2012

We propose a new speech privacy technique based on simple summation of numerous signals using N-channel loudspeakers. A speech signal mixed with high-level white or pink noise and with a delay set appropriately for each channel is reproduced by each loudspeaker to be synchronized at a specified sweet spot. At the sweet spot, SNR increases proportionally to the square root of N. A speech signal at and around the sweet spot is enhanced significantly, making it easily intelligible. Computer simulations were conducted assuming a linear array, a circular array, and a surrounding 157-loudspeaker array to estimate SNR and the Speech Intelligibility Index (SII). Results show that SNR and intelligibility in terms of SII effectively increase only at and near the sweet spot when using a surrounding 157-loudspeaker array. The SII at the sweet spot increases to 0.46, although those at areas distant from the sweet spot are nearly 0.
An identification of speaker-dependence in reverberant-robust speech recognition
Authors: Fukumori Takahiro , Morise Masanori , Nishiura Takanobu , Yamashita Yoichi
Published: April 2012

In recent years, a hands-free speech device has been developed with improving speech-recognition techniques. There is, however, a problem that the reverberant speech degrades the recognition performance in the field of distant-talking speech recognition. It is possibly addressed by taking preventive measures against the degradation of recognition performance with the reverberant criteria to estimate the recognition performance. We have already proposed the method to estimate recognition performance with ISO3382 acoustic parameter based on an impulse response. In this method, the recognition performance was estimated without speech features. Identification of the speaker with robust or weak features against reverberation makes it possible to adapt acoustic model for each speaker toward improving the recognition performance. In this research, we designed the speaker-dependence criteria in reverberant speech recognition. We first investigated existence of the speaker with robust or weak features against reverberation in various reverberant environments. After that, we compared clean and reverberant speech data in terms of speech features such as MFCC, delta MFCC, delta power, and utterance speed to evaluate the effects of reverberation on speech recognition. An experimental result showed the utterance speed was one of the effective candidates for the identification of speaker-dependence in reverberant-robust speech recognition.
Persymmetric adaptive detection of distributed targets in homogeneous environment
Authors: Hao Chengpeng , Ma Xiaochuan , Yan Shefeng , Xu Qi , Hou Chaohuan
Published: April 2012

In this paper, we deal with the problem of adaptive detection of distributed targets in Gaussian disturbance with unknown but persymmetric structured covariance matrix. A homogeneous environment is considered at the design stage, and a receiver based on the generalized likelihood ratio test (GLRT) is derived. Remarkably the new receiver ensures the constant false alarm rate (CFAR) property with respect to the covariance matrix of the disturbance. Finally, a performance assessment, conducted by Monte Carlo simulation, has shown that the new receiver can significantly outperform its unstructured counterpart due to embedded a priori knowledge about the structure of the disturbance covariance matrix, especially in a severely heterogeneous scenario where a very small number of training data is available.
Design and implementation of an acoustic signal acquisition system based on Wi-Fi
Authors: Li Xin
Published: April 2012

This paper presents an acoustic signal acquisition system based on Wi-Fi aimed at acquiring real-time acoustic signals and vibration signals, and transferring them to a center server for further processing and analyzing. In this design, the system is a three-layer hierarchy consisting of wireless nodes, access point (AP) managers and a center server. The center server manages all AP managers and receives signals from them. Wireless nodes can search for the desired AP according to signal strength and are managed by the corresponding AP manager. And the robustness of the communication between AP managers and wireless nodes is enhanced by an improved heartbeat mechanism. The system has been applied into an existing acoustic signal acquisition system and desired performances have been achieved.
Determination of the physical parameters of systems with a time-domain approach
Authors: Chan Yum-Ji , Zhang Yumin
Published: April 2012

A time-domain method to analyze the effective stiffness, damping and mass of systems, such as a loudspeaker or a porous cavity, is presented. A time-domain approach is taken to show the phase variation of greater than 2π in transfer functions. With the help of the least-mean-square (LMS) algorithm, the impulse response can be sought by feeding random noise into the systems. The impulse response is then used to deduce the effective stiffness, damping and mass of the system. Experimental demonstration with shunt loudspeakers is presented, and the traditional approach of analyzing air cavities filled with porous material is evaluated.
Detection of broadband sound sources using a randomly spaced linear array
Authors: Zampolli Mario , Fillinger Laurent , Hunter Alan J. , Clarijs Martijn C.
Published: April 2012

Arrays are commonly used in relatively narrow band applications. The array design and processing are usually optimized in order to maximize the gain in the look-direction, while minimizing the interference from sources located in other directions (but possibly not far off from the look-direction). This led for instance to the definition of minimum redundancy linear arrays that maximize the resolution for a given number of sensors. This maximization is, however, effective only at the design frequency of the array. For many active applications (such as active sonar or radar), which are narrow band in essence, this limitation is not an issue. However, if the signal to be detected in its entirety has a broadband frequency content, optimizing the performance of the array at a given frequency leads to possibly poor performance at other frequencies. Since optimal performance cannot be achieved at all frequencies simultaneously, one can aim for sub-optimal but useful performance throughout the entire frequency band. One possibility for achieving this is based on the use of a random hydrophone spacing. The effectiveness of the approach is investigated using simulations and is illustrated with experimental data collected using a randomly spaced linear array.
Investigation of the horizontal directivity of underwater ambient noise with the circular hydrophone array
Authors: Yang Shi , Yixin Yang , Yuanliang Ma
Published: April 2012

The ambient noise field in shallow water is highly variable in time and space. The horizontal directivity pattern of ambient noise is anisotropic and can be exploited for source localization in sonar signal processing. In the present work, the 12-element circular hydrophone array with radius of 1 meter was designed and used to observe the ambient noise in the shallow water experiment in the Yellow Sea. The MVDR beamformer with diagonal loading was designed to get the horizontal directivity pattern in frequency band of 1kHz to 3kHz. The conventional beamformer was used to analyze the horizontal directivity of ambient noise above 3 kHz. The noise data were sampled at 25kHz, bandpass filtered between 100Hz and 5kHz in the experiment. The horizontal directivity patterns at the experiment location at different frequencies were obtained based on above methods and the noise data. This work was supported by the National Natural Science Foundation of China(10734030)
Examination of the complex signals distribution conditions influence
Authors: Akulichev V.A. , Golov A.A. , Kamenev S.I. , Morgunov Yu.N.
Published: April 2012

Solving tasks of underwater acoustic communication and navigation for controlling underwater objects much depends on right hydrology and acoustic media condition estimation in operation area. Technically and economically it is worth to deploy on a operation area a stationary source of navigational and communication signals system with the range of functioning equal to operation area maximum size. For navigational system tasks each source in direct period of time beam a unique signal, which is recognized by underwater object and then propagation time and distance is been calculated. In this examination the using of a complex phase manipulated signals with carrier frequency 2000 Hz and 6000 Hz as sounding signals is been tested. These signals were used for transmitting information and navigational data. Beside their beam let to measure and examine waveguide impulse characteristics on the acoustic tracks. In current work the experiment results of informational signal transfer in case of shelf sea is shown.
Recognition of ship echo signal applying wigner distribution feature
Authors: Peng Yuan , Li Guijuan , Wang Xin , Lin Zhengqing
Published: April 2012

Recognition of ship echo signal's difficulty lies in extracting effective feature from target reflection signal. Researches show that target echo signal is double grading with time and frequency, so time-frequency is a effective way in the field of echo signal recognition. Wigner distribution is a real means of time-frequency analysis, but it is limited by its false time-frequency spectrum called interference item. In the paper, on the basis of studying the theory of interference item generation and reduction, Choi-Williams kernel function and self frequency-window methods are applied to implement Wigner's interference reduction. Through simulation test using typical signal such as multicomponent signal, Merits and drawbacks of the two means are also analyzed. Then to merchant ship, reef and reverberation, three kinds of CW echo signal, the interesting time-frequency features are extracted. At last, sample sets of above three kinds of echo signals are divided into training and testing sample sets. The number of training samples to the number of testing samples ratio is 1 to 4. The training samples are regarded as typical sample and input to Fuzzy Adaption Resonance Theory (FART) network to train. According to typical samples, the testing samples are tested by the same network. The results show that self frequency-window is a better means to reduce interference item. But high recognition rate can be achieved if interference items exist.
Performance of least mean square equalizer in shallow water acoustic communication channel
Authors: Yoon Jong Rak , Park Kyu-Chil , Park Jihyun , Shin Jungchae , Lee Seung-Wook
Published: April 2012

In shallow water, a transmitted signal is severely influenced by sea surface and bottom boundaries. Every signal to receiver except the signals through the water medium experiences a time-variant scattering in the sea surface and grazing-angle-dependent bottom reflection loss in the bottom. Consequently, the performance of underwater acoustic communication systems is degraded, and high-speed digital communication is disrupted by inter-symbol interference (ISI) effect. In this study, least mean square (LMS) algorithm equalizer is adopted to cancel out ISI effect. The equalizer is implemented in underwater acoustic communication system. Experiment is conducted in 26 m depth littoral ocean and the standard Lenna image which consists of 50x50 pixels and 8 bits per pixel is transmitted. It is verified that equalization is an efficient way to achieve high transmission rate in shallow water acoustic communication channel. This work was supported by Research Programs of Hanwha Corporation 2011.
Performance analysis of anti-multipath fading underwater acoustic communication (AMF-UAC) system in the ocean environmental variability
Authors: Kim Jangeun , Shim Taebo , Jeong Euicheol , Na Youngnam
Published: April 2012

Due to surface and bottom space constraints of the underwater acoustic channel, multi-path fading occurs and causes degradation of communication. Multi-path fading depending on the maximum delay time(Tm) and symbol period(Ts) can be divided into two kinds of channels. In this paper, we propose Anti-Multipath Fading Underwater Acoustic Communication(AMF-UAC) System. This system estimates the kind of channel and distinguishes flat fading (TmTs) under the ocean environmental variability. After checking the channel status, this system selects a mitigation technique depending on the type of multipath fading. In order to verify AMF-UAC system performance, we test transmission of image using 43.2kbit of gray image through the multi-path fading channel. Test results show that the number of bit errors is reduced from 300 to 10 under flat fading channel and from 20,000 to 90 under frequency selective fading channel when the reference SNR is 14dB.
A simple distributed networking protocol for underwater acoustic networks
Authors: Wang Yongfeng , Wu Yongqing , Zhang Chunhua , Cai Huizhi
Published: April 2012

A simple distributed networking protocol for underwater acoustic networks is proposed. Each node in the network learns about the degrees of its separation to a certain destination node by passively analysis the packets transmitted from its immediate neighbors. The address of neighboring node with the least hops to a certain destination node will then be saved in a route table as the relay address for later communication with that destination. The route table is initialized with broadcast address and the relay address to a destination node will be reset to broadcast address if no packets from the destination have been heard through the corresponding neighbor for a given time. By applying such a decay mechanism, the routing information is locally updated to keep up with the topology changes of the network due to mobility, node failure, and channel variations. There is little overhead traffic for networking and the network-wide flooding only happens in the initialization process, the proposed protocol is energy efficient. The details of the protocol and evaluation and simulation results are given in the paper.
Geoacoustic characteristics of P-wave velocity in Donghae City–Ulleung Island line, East Sea (Sea of Japan)
Authors: Ryang Woo-Hun , Kim Seong-Pil , Choi Jin-Hyuk
Published: April 2012

Donghae City–Ulleung Island Line (DC-UI Line) is a representative line for underwater and geoacoustic modeling in the middle western East Sea (Sea of Japan). In this line, an integrated model of P-wave velocity is proposed for a low-frequency range target (<200 Hz), based on high-resolution seismic profiles (2–7 kHz sonar and air-gun), shallow and deep cores (grab, piston, and Portable Remote Operated Drilling), and outcrop geology (Tertiary rocks and the basement on land). The basement comprises 3 geoacoustic layers of P-wave velocity ranging from 3750 to 5550 m/s. The overlying sediments consist of 7 layers of P-wave velocities ranging from 1500 to 1900 m/s. The bottom model shows that the structure is very irregular and the velocity is also variable with both vertical and lateral extension. In this area, seabed and underwater acousticians should consider that low-frequency acoustic modeling is very range-dependent and a detailed geoacoustic model is necessary for better modeling of acoustic propagation such as long-range surveillance of submarines and monitoring of currents. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0025733) and by the Ministry of Knowledge Economy through the grant of Marine Geology and Geophysical Mapping Project (GP2010-013).
Sonar detection performance analysis with environmental uncertainty using vertical array data
Authors: Ren Xinmin , Zheng Guofeng , LI Qihu , Sun Guiqing , Huang Haining , Lin Ju
Published: April 2012

Sonar detection performance is related to ocean environmental parameters, such as the source position, the ocean depth, the sound speed profile and geoacoustic parameters, etc. These parameters have strong spatial and temporal variability, which result to environmental uncertainty. The sonar detection system can be limited by the presence of environmental uncertainty. Based on a statistical model of the environmental uncertainty, the optimal Bayesian predictor by L. Sha has been applied in this paper to analyze the effects of environmental uncertainty on detection performance using vertical array data collected in two experiments. The first experiment took place in shallow water off the Italian west coast by the NATO SACLANT Center in 1993(SACLANT Sonar Data). The second experiment took place in shallow water in China in 2008(LOFAR'08 data). Quantitative effects of various uncertain parameters on detection performance have been illustrated to evaluate which one is the most sensitive and which one is insignificant. The present work is supported by the National Defense Fundamental Fund of China (No.613xxxxx).
Spherical Acoustic Lens for 3D Imaging SONAR
Authors: Takano Shinta , Ikeda Teiichiro , Hashiba Kunio , Sato Shinsuke , Kato Kentaro , Nanri Mitsuhiko
Published: April 2012

The states of the structures within a harbor after underwater construction or after a disaster are mainly visually checked and confirmed by divers. A new method that is independent of the water turbidity is desired to replace this direct diver necessity. In this study, we propose a spherical acoustic lens consisting of two or more concentric layers for use in a real-time three-dimensional imaging SONAR, which has many advantages. It does not require electronic circuitry for the beam forming, and it has a wide field of view and can simultaneously collect signals from various directions. The acoustical characteristics of the spherical lens are analyzed under conditions in which the speed of sound of the lens materials by using a finite difference time domain (FDTD) method. The results show that the spherical lens has a narrower receive beam profile and a higher receive gain than conventional compound lenses consisting of three aspheric lens.
A delay-sensitive gts allocation scheme in ieee 802.15.4 for wireless audio applications
Authors: Wang Ying , Zhang Peng , Yang Jun
Published: April 2012

The IEEE 802.15.4 standard is designed for low rate wireless personal area networks, targeting at low cost and low power communications. It also provides a guaranteed time slot (GTS) mechanism to support time sensitive wireless audio applications. The coordinator allocates specific durations within a superframe to guarantee reliability and performance of data deliveries. However the existing first-come-first-served (FCFS) GTS allocation policy can result in the scheduling inflexibility in low-latency data transmission, since it doesn't take into account the traffic specification, delay requirements and the energy resources. In this paper, an adaptive GTS allocation scheme is developed to satisfy the delay constraints of wireless audio applications. Based on recent GTS usage feedback, each device in the WPAN is dynamically allocated a priority number. Then the devices are allocated specific slots according to this priority information. The devices with higher priorities indicate more recent traffic and have higher probabilities to transmit their data in the subsequent superframe. The performance of the scheme is analyzed using Markov chain. The analytical model is validated through simulation results, indicating that the proposed adaptive scheme has better performance for audio transmissions.
Evaluation of differences in perceived overall acoustical quality and listener envelopment from binaural recordings in a 900-seat hall
Authors: Vigeant Michelle C. , Daly Jenna M. , Dick Michael J.
Published: April 2012

Impulse response measurements and binaural recordings were taken in a 900-seat multi-purpose hall in three clusters of nine adjacent seats. Each cluster contained a central seat, the seats immediately to the left and to the right, and the three seats in the rows directly in front of and behind the central seat. Differences between the seats were analyzed in terms of the standard room measures and spatial measures lateral energy fraction (LF) and late lateral energy level (GLL). The typical JNDs were used to evaluate the differences between seat pairs within a given cluster. Differences on the order of 1 or more JNDs were found between most seat pairs within a cluster in most octave bands between 125 Hz to 4000 Hz for early decay time, clarity index, strength, and LF. In terms of GLL, the average difference between pairs of seats was 0.6 dB. However, a total of 14 pairs of seats had differences in GLL between 1.0 to 2.0 dB. A listening test was carried out to determine if subjects could hear differences in the binaural recordings in terms of the listener envelopment and overall acoustical quality. The measurement and subjective test data will be presented.
Study of cetaceans in Istanbul Strait using passive acoustic method
Authors: Kameyama Saho , Dede Ayhan , Ozturk Ayaka A. , Akamatsu Tomonari , Tonay Arda M. , Ozturk Bayram , Arai Nobuaki
Published: April 2012

The Istanbul Strait connects to the Aegean Sea and the Black Sea. Three cetaceans appear in this Strait, harbor porpoise (Phocoena phocoena relicta), common dolphin (Delphinus delphis ponticus), bottlenose dolphin (Tursiops truncatus ponticus). We used stereo passive acoustic monitoring system (A-tag) to monitor the moving pattern of these cetaceans from July 2009 to September 2010. This system enables to record the sound source direction calculated by the sound arrival time difference between two hydrophones. They have different frequency sensitivity, which enable to distinguish Phocoenidae from Delphinidae. Phocoenidae and Delphinidae were detected most frequently in April. They stay near the A-tag in March and April than in August. Acoustic sensing distance, which is proportional to the inter-click-interval of the sonar signals, was short in the same months. This was more clear in Phocoenidae. Dominant behavior pattern of both species was staying rather than moving in all seasons. However, Phocoenidae did not stay long time in August. Moving behavior was associated with longer sensing distance comparing with staying. Especially in August, short distance sensing was less frequent in Phocoenidae. All these findings suggest that cetaceans may feed in this area mainly in March and April and travel in August.
Optical scanning photoacoustic microscopy with acoustic near-field detection
Authors: Chen Hsin-Yu
Published: April 2012

Photoacoustic microscopy (PAM) can be used to provides high-resolution microscopic images with contrast determined by optical absorption differences. Nevertheless, contemporary PAM suffers from low image acquisition speed, and the resolution depends crucially on accuracy of confocal alignment. To overcome these problems, we propose near-field acoustic detection, with which image resolution is solely determined by laser spot size and a MEMS based optical mirror for rapid 2D scanning. Phantom studies have been conducted to characterize performance of this prototype device. With a hair phantom, the lateral resolution is assessed at 14.0um. Further improvement is possible if the fiber-lens coupling can be made more precise. The axial resolution approximates 50um, which corresponds to the wavelength of a 30MHz ultrasound frequency in water. Relationship between the photoacoustic signal amplitude and absorption coefficient of the image object is approximately linear, with a 0.95 correlation coefficient after first-order regression fit. Noise equivalent pressure(NEP) reaches 49.11(Pa), which is comparable to other PAM systems. For high speed image data acquisition, we used a MEMS optical scanning mirror. The commercial scanning mirror raster-scans the laser beam across 130+ pixels per second. This design not only increases frame rate, but reduces the overall device dimensions. In addition to typical applications such as microscopic imaging of biological tissues, we demonstrate the potential of this device in nondestructive testing by inspecting the surface quality of carbon based glucose test strip, a disposable component in glucose meters.
A prototype of total-internal-reflection type of microphone using optical fibers
Authors: Suzuki Yasushi , Kido Ken'iti
Published: April 2012

This paper describes a new type of microphone which uses the total internal reflection at the curved interface between glass and air. The critical angle for total reflection changes by the refractive index of air, which depends on the air density. As the density changes by the sound pressure, the sound pressure is measurable by detecting the intensity of the reflected light from the total reflection area. The acoustical characteristics of a prototype of the proposed microphone using optical fibers as an optical transmission path are investigated experimentally. The experimental results show that although the sensitivity of the microphone is low in the present stage, it can be used for the measurement of great volume of sound. The microphone has no limitation in the frequency range in principle because the mechanical vibration is not used.
Theoretical analysis on shear horizontal polarized surface acoustic waves propagation in periodic metal grating using the variational method
Authors: Xu FangQian
Published: April 2012

A new theoretical method is presented to analyze dispersion characteristics of SH-type SAWs propagating on periodic metallic grating structures using the variational theory and coupling-of-modes (COM) equations. The characteristics of SH-type SAWs propagating in short-circuited Al gratings on various crystals are studied and the calculated results agree well with those of typical Hashimoto's method. Also, some involved problems like dispersion parameters of SH-SAW along the ST-90oX quartz with Al electrode were first described. The advantages of this method are that the complicate Green's function is avoided, resulting in simple, clear and fast theoretical analysis.
Measurement of vibration distribution on focusing source using a thin rod reflector
Authors: Yanagisawa Hirokazu , Kim Jung-Ho , Saito Shigemi
Published: April 2012

Utilizing the concept of time reversal and the transmitter-receiver reciprocity, the distribution of the vibration amplitude and phase is estimated for a focusing source without using a hydrophone. When a tone burst wave is radiated in water, the sound wave reflected from the top of a thin rod is detected with the concave source itself. Scanning the reflector surface in the plane normal to the acoustic axis, two-dimensional data of the amplitude and phase of the output voltage are stored and then the calculations of square root and time reversal are executed for the data. Comparing with the case detecting the sound with a needle type hydrophone set at the same position as the reflector, the advantage and disadvantage of the present method are discussed taking a piezoelectric concave source with a star-shape electrode for instance. The experiment is also carried out for the high-frequency concave-source with an aperture radius of 4 mm which is too small to measure with an ordinary hydrophone.
Sound source distance estimation using a small-size microphone array
Authors: Esaki Satoshi , Nishino Takanori , Takeda Kazuya
Published: April 2012

A method for estimating the sound source depth, i.e., the distance between a source and receiver, using a small-size array is proposed. The proposed method uses the spatial distribution pattern of quasi-independent signal components obtained by the frequency-domain independent component analysis (FDICA) as the cue for depth estimation. The quasi-independent components are calculated by applying FDICA to array signals with very high redundancy, for example, 60 microphone signals for a pair of sources; therefore, signal components associated with reflection signals are obtained even though they are correlated with the direct signal. Experimental evaluation using a small-size microphone array with a large number of elements confirms that the average (RMS) estimation error of the proposed method is 0.33 m, which is sufficiently accurate for our applications.
Precise simulation of surface acoustic wave devices using frequency-dependent coupling-of-modes parameters
Authors: Wang Hao , Wang Weibiao , Wu Haodong , Su Bo , Shui Yongan
Published: April 2012

Surface acoustic wave (SAW) devices have been extensively applied as the core components of modern mobile communication systems. In the fierce competition, developing precise and fast simulation models is very important. The widely-used coupling-of-modes (COM) model has been improved for many times, but it is still not satisfied yet. The fatal problem of extracting frequency-dependent COM parameters is that the reflection coefficient and the propagation velocity could not be obtained independently. In this work, a new method to evaluate all the frequency-dependent COM parameters is proposed. Using the FEM/BEM tool, the field distributions (including mechanical displacements and potential distribution) of forward and backward surface acoustic waves within periodic gratings of finite length could be calculated at every frequency. From the characteristics of the field distribution curves, all the COM parameters are evaluated as functions of frequency, and in particular, the reflection coefficient and the propagation velocity are extracted independently. Using these frequency-dependent COM parameters, the one-port resonators on the substrates of 128° YX-LiNbO3, ST-Quartz and 42° YX-LiTaO3 are simulated, which show good agreement with the results by FEM/BEM. The results verify the validity of the method. This work is supported by Natural Science Foundation of China under Grant No. 10774073 & 11174143.
The use of parametric array for measuring absorption coefficient of sound absorbing material
Authors: Kuang Zheng , Yang Jun
Published: April 2012

The measurements of the absorption coefficient of sound absorbing materials are mainly using the standing wave tube or the reverberant room. Both of them are not suitable for measurement in situ. Based on the high directional property of the self-demodulated sound from parametric array, the absorption coefficients of the material can be measured in situ. However, the spurious noise signals generated by nonlinear interaction between the high intensity primary sound and the microphone reduce the accuracy of the measurement results especially at the low frequency range. To solve the problem, phase-cancellation method is introduced into the measurement. The transmitters of parametric array are divided into two parts radiating the primary sound with opposite phases. Experimental results demonstrate that the method decreases the primary sound significantly along the axial direction in the near-field with little influence on the audible sound field, which can satisfy the requirement of the measurement.
Finite element simulation of Lamb wave scattering at delamination damage in composite laminates
Authors: Zhang Haiyan
Published: April 2012

Due to the anisotropy and multilayer characteristics of composite laminates, the analytical solution for Lamb wave scattering at delamination damage do not exist. This study explores the effectiveness of the 2D finite element method (FEM) to model Lamb wave scattering at a delamination which is across the full width of the composite laminates. The capability of 2D FEM to simulate Lamb wave scattering characteristics at delaminations with different sizes by means of contour snapshots at different time instances and the scattering directivity pattern in different laminated location are illustrated. The results suggest that 2D FEM can be used to investigate Lamb wave propagation and their scattering characteristics at delamination damage, which help to validate and improve the performance of Lamb wave damage detection configuration.
Two-dimensional analysis of FBAR by using FDTD method
Authors: Yu Xiaoli , Cao Ming , Luo Zhongyong , Gong Xun , Zhang De
Published: April 2012

The film bulk acoustic resonator (FBAR) devices are lighter, smaller, cheaper and capable of dealing with larger power than SAW devices. Therefore, the FBAR technology is more competitive in satisfying the commands of modern mobile phone systems. In this paper, the finite-difference time-domain method is applied to analyze the two-dimensional thin-film bulk acoustic wave resonators. The piezoelectric governing equations and Newton's equation of motion are discretized to centered finite-differences in spatial and temporal domain. An electrostatic field simulator named ANSOFT Maxwell 2D is used to calculate the electric field intensity. The frequency domain electrical impedance characteristics of FBAR with different electrode thicknesses are calculated by using the Prony's method. From the simulation results, the optimal electrode thickness is suggested.
Comparative study of unsteady loudness models for mechanical and real sounds
Authors: Novak Colin , Ule Helen , Charbonneau Jeremy , Letowski Tomasz
Published: April 2012

While noise levels are most often quantified using physical quantities including A-weighted sound pressure level, these metrics do not adequately represent the human perception of the noise. For this, loudness is a more appropriate acoustic metric as it describes the perceived acoustic intensity of a sound. Given that real sounds are often unsteady, a most useful loudness calculation will also account for the perceptional phenomena of time and temporal masking. Studies have been done which demonstrate the performance of several loudness models for pure tone sounds and compare these results to the ISO 226 equal loudness curves. This investigation goes beyond that and evaluates the performance of two unsteady loudness models, the Glasberg and Moore model and the DIN 45631-A1 method, using mechanical and real life sounds. Through implementation ofa jury, the differences of the two loudness calculation methods are demonstrated by plotting the perceived loudness of the sounds for two different levels compared to two different reference levels.
Development of a high quality wireless sound reinforcement system
Authors: Liu Li , Zhang Peng , Yang Jun
Published: April 2012

This paper describes the development and initial application of a wireless sound reinforcement system. This system consists of wireless communication module, digital signal processor (DSP) and audio codec. Signal processing algorithms are used to achieve high quality wireless voice communications and audio playback. To this end, howling suppression algorithm is implemented using DSP. To date, there are three widely used methods for acoustic feedback control: phase-modulating feedback control (PFC), adaptive feedback cancellation (AFC), and notch-filter-based howling suppression (NHS). In this system, we used an adaptive notch filter (ANF) to perform feedback controlling. Simulation Results indicates the effect of this algorithm in suppressing howling. Furthermore, the control strategy of the algorithm is optimized by experiments in a conference room environment. The experimental results show the performance of this system in the real environment.
Differences in responses to vibration induced in residential environments by railway and construction activities
Authors: Woodcock James , Peris Eulalia , Sica Gennaro , Moorhouse Andy , Waddington David
Published: April 2012

This paper summarises the results of the Defra (UK) funded project `NANR209: Human response to vibration in residential environments'. The main aim of this project was to develop exposure-response relationships for the human response to environmental vibration as experienced by residents in their own homes. The sources of vibration considered were railway, construction, and internal sources outside of the resident's control. In this study, 1431 questionnaires were completed with UK residents in their own homes to determine self reported annoyance. Measurements of vibration inside and outside residences were conducted to determine each resident's vibration exposure. Presented in this paper are the exposure-response relationships derived from these data indicating the percentage of people expressing annoyance above a given threshold for a given vibration exposure. In particular, this paper reports the differences in responses to vibration induced by railway and construction activities. [Work funded by the Department for Environment, Food and Rural Affairs (Defra) UK]
Noise policy development in Italy and the EU
Authors: Licitra Gaetano , Ascari Elena
Published: April 2012

Since the approval of European Directive 49/2005, in Europe many studies and developments have been done to improve quality and accuracy of noise mapping and action planning. With the end of the first round of agglomerations mapping, a comparison between mapping methods and exposure of cities is available. In Italy, tests have been done to compare procedures and results of different cities to understand how to improve quality and effectiveness of noise maps. In the meantime, EU Community worked to change calculation methods in order to find a procedure adaptable for each country but with a common structure. In fact, we have already seen that each country, also using an interim method has produced very different results. In particular, example within Italian maps will be shown and also between ones of different countries in Europe. The level assignment method to population will change too, in order to move towards a more realistic photograph of health conditions: maximum level was too preventive, when considering large building, so a new method has been taken from the German procedure such that each dwelling/room has his own level. Some example of the effects of this change will be evidenced in this paper.
Limitations caused by radiation damping and water viscosity on power delivered by ocean wave energy conversion devices
Authors: Thiam Amadou G. , Pierce Allan D.
Published: April 2012

Any generic ocean wave energy conversion device can be suitably “tuned,” given various design constraints, to extract the maximum amount of power from a given incoming ocean wave. Just how large this maximum extracted power can be depends to some extent on the magnitudes associated with the various natural damping mechanisms that inhibit the driven oscillations of the device. Such mechanisms include (i) the excitation of ocean waves by the oscillating body and (ii) the friction-induced drag when the body's surface moves relative to the neighboring water. One can generally quantity the joint influence of these mechanisms with a “bobbing test,” where an object is initially displaced downward and allowed to freely oscillate, the oscillations dying out exponentially. The authors' general experience is that such a decay typically corresponds to a Q of about 5. Simple analytical models are described to quantify the two mechanisms. For viscous damping, the applicable fundamental model is that which yields a friction force on a flat plate oscillating below a nominally stationary incompressible fluid. For the radiation damping, the theory uses the Green's function solution for a point volume source just below the free surface of an incompressible fluid under the influence of gravity.
Study on effect of dynamic lubricated bearing oil film stiffness on underwater structure acoustic radiation induced by propeller force
Authors: Yang Jiayou , Cao Yipeng , Li Liaoyuan
Published: April 2012

When propeller runs in the unsteady wake flow field, the exciting force can form in the propeller blades. Such propeller exciting force transfers from the shafting, bearing supporting to the structure, causes the underwater structure strong vibration and noise. The vibration of propeller-shafting-structure coupled system is one of the main sources of underwater structure radiated noise now. Different oil film stiffness will affect the input power transmission characteristics of coupled system severely, and then affect the vibration and noise analysis of underwater structure. In this paper, the finite element model of double cylindrical shell structure with shafting is built. The oil film stiffness is got by solving two-dimensional Reynolds equation based on finite difference method. The vibration and underwater noise radiation of the shell structure induced by propeller excite force are calculated by FEM/BEM. Finally, the effect of dynamic lubricated bearing oil film stiffness on underwater structure acoustic radiation induced by propeller force is analyzed.
The long-term effects of aircraft noise exposure on children's cognition: findings from the UK RANCH follow-up study
Authors: Clark Charlotte , Head Jenny , Stansfeld Stephen
Published: April 2012

Many studies have demonstrated that environmental noise exposure at school is associated with poorer reading ability. However, studies have yet to determine the long-term consequences of environmental noise exposure during school for later developmental outcomes. This paper presents a longitudinal follow-up of the UK RANCH cohort assessing whether aircraft noise exposure in primary school is associated with poorer reading comprehension in secondary school. The original RANCH study found a relationship between aircraft noise exposure at primary school and children's reading comprehension for 9-10 year old children attending schools around London Heathrow, Amsterdam Schiphol and Madrid Barajas airports. Six years after the original study, 461 participants aged 15-16y (48% of the UK baseline sample) completed a standardised reading test during group testing in their classroom. Aircraft noise exposure at school was assessed using Leaq16 contour data. Analyses found no significant effect of aircraft noise exposure at primary school or secondary school on reading comprehension assessed at secondary school, although there was a trend for both types of noise exposure to be associated with poorer reading comprehension. The study is limited by its small sample but the findings indicate that aircraft noise exposure at school could have long-term implications for children's cognitive development.
Temporal and spatial characteristics of noise in train stations
Authors: Soeta Yoshiharu , Shimokura Ryota
Published: April 2012

The train noise in station (TNIS) can annoy passengers and reduce the speech intelligibility of the public address system in a station. Thus clarifying the acoustical characteristics of TNIS is important for the comfort and safety. Noise level was evaluated the equivalent continuous sound pressure level (LAeq). The sound diffuseness was evaluated by the interaural cross-correlation coefficient (IACC) from the interaural cross-correlation function. The pitch and pitch strength was evaluated by the delay time (t1) and amplitude (f1) of the first peak of the autocorrelation function. The LAeq and IACC of the TNIS in the underground station were higher and lower, respectively, than those in the ground station. The t1 and f1 of the TNIS in the underground station were stable and lower, respectively, than those in the ground station. When the train came into the station, the LAeq of the TNIS at the island platform were higher than that at the side platform. The result suggests that the underground island platform, which is one platform at the center and the rail tracks on the both sides, needs improvement in particular although it is most frequently adopted as newly constructed stations in Japan.
Noise reduction by eaves/louvers attached on façade of high-rise buildings
Authors: Sakamoto Shinichi , Asakura Takumi
Published: April 2012

The authors have been investigating noise reduction effects of several types of eaves/louvers attached on façade of high-rise buildings. The eaves are originally used for the aim of shading of solar radiation or as structures for fire-proofing in Japan, but the devices can also provide high effectiveness of noise reduction against road traffic. The authors have revealed such effects through wave-based numerical analyses, scale model experiments and in-situ experiment. The eaves attached on the façade work as either noise shielding materials or noise reflectors, so inclined eaves at higher rooms have more effectiveness of noise reduction. The effectiveness varies with protrusion length of the eave, inclination angle, height of the room and so on. In this paper, such results of our investigation on noise reduction by eaves and louvers will be presented.
Micorcrack localization in pipelines using nonlinear guided waves combined with time reversal
Authors: Guo Xiasheng , Yang Di , Zhang Dong
Published: April 2012

A three-dimensional (3D) micro-crack imaging technique is proposed for pipeline inspections. With non-classical nonlinear guided waves generated from micro-cracks recorded, the third harmonic waves are used to image the fatigued crack, with the help of time reversal process. A finite-difference time-domain (FDTD) code is programmed to solve the wave equations under cylindrical coordinates, and simulate the wave propagation process. A defect with hysteretic stress-strain behavior is embedded in the model; its interaction with guided waves generates nonlinear components, the harmonic components are time reversed and played back into the pipe, hence produce the image of the cracked area. The results show excellent spatial retrofocusing capability. The accuracy of localization depends on crack orientation angle and an adopted guided wave mode. [This work is supported by the National Natural Science Foundation of China (11104140) and Natural Science Foundation of Jiangsu Province (BK2011543)]