APPLICATION OF DOMAIN DECOMPOSITION IN ACOUSTIC AND STRUCTURAL ACOUSTIC ANALYSIS

Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts. For high-frequency applications, probabilistic techniques, such as statistical energy analysis （SEA）, are used. For mid-frequency range, currently no adequate and mature simulation methods exist. Recently, wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range. In contrast with the element based methods, no discretization is required. A sufficient, but not necessary, condition for convergence of this method is that the acoustic problem domain is convex. Non-convex domains have to be partitioned into a number of （convex） subdomains. At the interfaces between subdomains, specific coupling conditions have to be imposed. The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy. The results show the new technique can be applied up to much higher frequencies.

Acoustic Analysis of EkeGusii Vowel System

This study describes the vowel system of EkeGusii(“Bantu E.42”)(Guthrie,1948)in an acoustic phonetics perspective using oral data got from purposively sampled subjects:four adult males,four adult females and four children(two boys and two girls all 8 years old)equally from the two dialects of EkeGusii(EkeMaate and EkeRogoro Dialects).In order to capture the distribution characteristics of the vowel acoustic concentration,the group frequency means are normalized using Lobanov’s(1971)algorithm.Two viewpoints are the subjects of analysis in EkeGusii vowels:(a)acoustic vowel space as projected by the intersection of F2 vs.F1 or quadrilateral,and(b)spatial features of high,low,front and back.These qualities are mainly influenced by the physiology of speakers and social variability as occasioned by gender,age and dialect.The results indicate that children have no gender difference in formants,and have the highest frequencies for all formants,followed by adult females and then adult males.Furthermore,acoustic vowel space and spatial features are affected by gender,age,and dialect.A vowel pattern,replicated by all informants,is realized in the dispersion of the vowels within the chart influenced by gender and age.This study found out that EkeGusii seems to adopt a seven-vowel system of/i eɛaɔo u/with a length contrast.

Localized Method of Fundamental Solutions for Acoustic Analysis Inside a Car Cavity with Sound-Absorbing Material

This paper documents the first attempt to apply a localized method of fundamental solutions(LMFS)to the acoustic analysis of car cavity containing soundabsorbing materials.The LMFS is a recently developed meshless approach with the merits of being mathematically simple,numerically accurate,and requiring less computer time and storage.Compared with the traditional method of fundamental solutions(MFS)with a full interpolation matrix,the LMFS can obtain a sparse banded linear algebraic system,and can circumvent the perplexing issue of fictitious boundary encountered in the MFS for complex solution domains.In the LMFS,only circular or spherical fictitious boundary is involved.Based on these advantages,the method can be regarded as a competitive alternative to the standard method,especially for high-dimensional and large-scale problems.Three benchmark numerical examples are provided to verify the effectiveness and performance of the present method for the solution of car cavity acoustic problems with impedance conditions.

An acoustic analysis of vowels in checked syllables in Chinese

Vowels in checked syllables are almost short and abrupt in Chinese Mandarin dialects. This paper proposed a parametric statistical modeling for the analysis of these vowels.The parameters were described empirically with the method of probability distribution. The effects of the multiparameter classifications were estimated by the binary and multinomial logistic models, and the method of support vector machine was adopted to carry out the pattern recognition of the classifications. The results show that the parameters of duration, DCT_（1-3）are significant to the external classification, and the parameters of DCT_（0-3） have significant main effects on the internal classification. The automatic testing shows that the hit rate of the external pattern recognition is only 43.6% but the rate is 96.1% of the internal. It indicates that the abrupt feature should be additive rather than distinctive.

Modeling and acoustic analysis of irregular sound enclosure by using Chebyshev-variational method

A modeling method for irregular sound enclosures was proposed based on the Chebyshev-variational theory. A rectangular space was first assumed to bound the irregular sound space and the sound pressure in the rectangular space expressed as a triple-Chebyshev series. Next, a coordinate transformation was performed and the Lagrangian functional of the irregular sound space obtained. Finally, the Lagrangian functional was solved under the Ritz method framework, and the enclosure＇s acoustic characteristic equation deduced and the eigenpairs obtained. The accuracy of the present method was validated according to agreement between the present results and finite element results for an enclosure with a curved surface.Furthermore, the acoustic characteristics of a trapezoidal enclosure and an enclosure with an inner groove were investigated. The results showed that the mode shapes of the trapezoidal sound space changed with increased inclination angle and the natural frequencies, except the first order, of the sound space with a rectangular inner groove decreased with increased groove depth.

Acoustic Analysis and Decision Tree-Based Shifting Hierarchical Approach for Prediction of Uyghur Prosodic Boundary

Correct prosodic boundary prediction is crucial for the quality of synthesized speech in text-to-speech system. This article mainly presents the prosodic hierarchy of Uyghur language, which belongs to Turkish language family of Altaic language system and further verifies the reliability of proposed Uyghur prosodic boundary annotation rules by acoustic analysis. In the prediction part, a two-layer shifting hierarchical approach based on decision tree is used for predicting prosodic word and prosodic phrase boundary, and the influence of different feature sets on the Uyghur prosodic boundary prediction is also investigated. Experimental results clearly show the acoustical changes and automatic prediction performance of different prosodic boundaries of Uyghur language, thus laying a good foundation for further research.

Topology Optimization of Sound-Absorbing Materials for Two-Dimensional Acoustic Problems Using Isogeometric Boundary Element Method

In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.Taking the element density of porousmaterials as the design variable,the volume of porousmaterials as the constraint,and the minimum sound pressure or maximum scattered sound power as the design goal,the topology optimization is carried out by solid isotropic material with penalization(SIMP)method.To get a limpid 0–1 distribution,a smoothing Heaviside-like function is proposed.To obtain the gradient value of the objective function,a sensitivity analysis method based on the adjoint variable method(AVM)is proposed.To find the optimal solution,the optimization problems are solved by the method of moving asymptotes(MMA)based on gradient information.Numerical examples verify the effectiveness of the proposed topology optimization method in the optimization process of two-dimensional acoustic problems.Furthermore,the optimal distribution of sound-absorbingmaterials is highly frequency-dependent and usually needs to be performed within a frequency band.

Acoustic emission assessment of interface cracking in thermal barrier coatings

In this paper,acoustic emission（AE） and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression.The interface failure process can be identifie via its AE features,including buckling,delamination incubation and spallation.According to the Fourier transformation of AE signals,there arefourdifferentfailuremodes：surfaceverticalcracks,opening and sliding interface cracks,and substrate deformation.The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz,whilst that of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.The energy released of the two types of interface cracks are 0.43 and 0.29 MHz,respectively.Based on the energy released from cracking and the AE signals,a relationship is established between the interface crack length and AE parameters,which is in good agreement with experimental results.

Male Advertisement Call of the Endangered Leptobrachella tengchongensis(Anura: Megophryidae) from Mount Gaoligongshan, Yunnan Province, China

We present the first description of the acoustic characters of the endangered Tengchong leaf litter toad(Leptobrachella tengchongensis), aiming to inform future ecological studies of the species and taxonomic studies in the genus Leptobrachella. A total of 1179 calls, belonging to 6 adults male individuals, were recorded using TASCAM DR-40 digital sound recorder from its type locality in May 2015 and then analyzed using Raven Pro v.1.6.1 software. The advertisement call of male L. tengchongensis consists of primary advertisement call and secondary advertisement call. The primary advertisement call is invariably composed of two notes and has a call duration of 61 ± 5 ms(23–87 ms, n = 1142). The secondary advertisement call is composed of 3–10 notes(mean 5.25 ± 1.41 notes/call, n = 37) with a call duration of 90 ± 6 ms(37–127 ms, n = 37). The mean inter-call interval is 212 ± 121 ms(88–1121 ms, n = 1092). An introductory note is absent in advertisement calls and the dominant of calls is 4.1–4.8 kHz(at 20 ℃). We discuss the interspecific and intraspecific variations on advertisement calls in L. tengchongensis and among Leptobrachella species, and provide a summary on the major acoustic characters of all Leptobrachella species occurring north of the Isthmus of Kra.

Profiles and predictors of onset based differences in vocal characteristics of adults with auditory neuropathy spectrum disorder(ANSD)

Purpose:Onset-based differences are understudied in Auditory Neuropathy Spectrum Disorder(ANSD)in dimensions such as voice,which is addressed in the study.The study aimed to profile and predict the best metrics of onset-related differences in acoustic vocal characteristics of early and late-onset ANSD patients.Methods:31 participants(15 early and 16 late-onset)aged 15e30 years diagnosed with ANSD were included in the study.The sustained phonation of vowel/i/recorded by the participants using android based smartphones of selected configuration was sent over email to the experimenter.Acoustic parameters(fundamental frequency,harmonic frequencies,jitter,shimmer,harmonic-to-noise ratio,cepstral peak prominence-CPP,and pitch sigma)were analysed using Praat software.Results:Results revealed significantly increased(p<0.05)fundamental frequency along with decreased F2 and F3 of/i/in the early-onset ANSD compared to the late-onset group,which can be explained based on differences in the pathophysiology of the disorder.Although not statistically significant,mean perturbations(jitter and shimmer),harmonic-to-noise ratio,cepstral peak prominence,and pitch sigma were more affected in the early-onset group,reflective of lowered auditory feedback and periodicity in their voice samples.Results of discriminant analysis marked the emergence of F2,F3,and CPP as the most sensitive metrics for onset-based group differences in voice characteristics.Conclusions:The findings from the study highlight the role of acoustical voice evaluation(especially CPP,F2&F3)in verifying the onset of ANSD disorder.The insights from the onset-based differences seen in vocal characteristics can indirectly help audiologists in deciding the management options for ANSD.

Influence of pontic design of anterior fixed dental prosthesis on speech: A clinical case study

BACKGROUND The pontic design of fixed dental prostheses(FDPs)is strongly associated with the phonetic function,and the phonetic function of anterior FDPs with different pontic designs remains understudied.AIM To investigate the immediate and short-term influence of pontic design of anterior FDPs on Chinese speech in a clinical case using objective acoustic analysis.METHODS Two FDPs with two types of pontic design(saddle pontic and modified ridge lap pontic)were fabricated for one patient with maxillary anterior teeth missing.The acoustic analysis of patient’s articulation was conducted immediately after wearing the FDPs and 1 wk after wearing these FDPs.RESULTS The effect of FDP on Chinese vowels(/a/,/o/,/e/,/i/,/u/,and/ü/)was insignificant,because the recovery of vowel distortion occurred within 1 wk for both FDPs.Three(/f/,/s/,and/sh/)of eight Chinese fricative consonants were found to have obvious distortions,and the/s/sound distortion last for more than 1 wk for the patient wearing FDP with modified ridge lap pontic design.CONCLUSION The influence of anterior FDP on articulation of Chinese vowels is insignificant,while the articulation of Chinese fricative consonants is more susceptible.When fabricating anterior FDPs for patients with speech related professions,saddle pontic design can be an alternative option compared with modified ridge lap pontic design.

Experimental prototyping of the adhesion braking control system design concept for a mechatronic bogie

The dynamic parameters of a roller rig vary as the adhesion level changes.The change in dynamics parameters needs to be analysed to estimate the adhesion level.One of these parameters is noise emanating from wheel–rail interaction.Most previous wheel–rail noise analysis has been conducted to mitigate those noises.However,in this paper,the noise is analysed to estimate the adhesion condition at the wheel–rail contact interface in combination with the other methodologies applied for this purpose.The adhesion level changes with changes in operational and environmental factors.To accurately estimate the adhesion level,the influence of those factors is included in this study.The testing and verification of the methodology required an accurate test prototype of the roller rig.In general,such testing and verification involve complex experimental works required by the intricate nature of the adhesion process and the integration of the different subsystems(i.e.controller,traction,braking).To this end,a new reduced-scale roller rig is developed to study the adhesion between wheel and rail roller contact.The various stages involved in the development of such a complex mechatronics system are described in this paper.Furthermore,the proposed brake control system was validated using the test rig under various adhesion conditions.The results indicate that the proposed brake controller has achieved a shorter stopping distance as compared to the conventional brake controller,and the brake control algorithm was able to maintain the operational condition even at the abrupt changes in adhesion condition.

Performance analysis and material distribution optimization for sound barriers using a semianalytical meshless method

With the increase in car ownership,traffic noise pollution has increased considerably and is one of the most severe types of noise pollution that affects living standards.Noise reduction by sound barriers is a common protective measure used in this country and abroad.The acoustic performance of a sound barrier is highly dependent on its shape and material.In this paper,a semianalytical meshless Burton-Miller‐type singular boundary method is proposed to analyze the acoustic performance of various shapes of sound barriers,and the distribution of sound‐absorbing materials on the surface of sound barriers is optimized by combining a solid isotropic material with a penalization method.The acoustic effect of the sound‐absorbing material is simplified as the acoustical impedance boundary condition.The objective of optimization is to minimize the sound pressure in a given reference plane.The volume of the sound‐absorbing material is used as a constraint.The density of the nodes covered with the sound‐absorbing material is used as the design variable.The method of moving asymptotes was used to update the design variables.This model completely avoids the mesh discretization process in the finite element method and requires only boundary nodes.In addition,the approach also does not require the singular integral calculation in the boundary element method.The method is illustrated and validated using numerical examples to demonstrate its accuracy and efficiency.

Optimal Design and Experimental Verification of Low Radiation Noise of Gearbox

Reducing the radiated noise of a gearbox is a difficult problem in aviation,navigation,machinery,and other fields.Structural improvement is the main means of noise reduction for a gearbox,and it is realized primarily through contribution analysis and structure optimization.However,these approaches have certain limitations.In this study,a low-noise design method for a gearbox that combines the two approaches is proposed,and experimental verification is performed.First,a finite element/boundary element model is established using a single-stage herringbone gearbox.Considering the vibration excitation of the gear system,the radiation noise of a single-stage gearbox is predicted based on the modal acoustic transfer vector(MATV)method.Subsequently,the maximum field point of the radiated noise is determined,and the acoustic transfer vector(ATV)analysis and modal acoustic contribution(MAC)analysis are conducted to determine the region that contributes significantly to the radiated noise of the field point.The optimization region is selected through the panel acoustic contribution(PAC)analysis.Next,to reduce the normal speed in the optimization region,topology optimization is performed.According to the topology optimization results,four different noise reduction structures are added to the gearbox,and the low-noise optimization models are established respectively.Finally,by measuring the radiated noise of the gearbox before and after optimization under a given working condition,the validity of the radiated noise prediction method and the low-noise optimization design method are verified by comparing the simulation and experimental data.A comparison of the four optimization models proves that the noise reduction effect can be achieved only by adding a noise reduction structure to the center of the density nephogram.

Feature analysis of acoustic emission sources for rail crack detection by the finite element method

The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inner cracks in rail. In order to obtain the features of Acoustic Emission （AE） sources of inner cracks in rail, AE sources with different types, depths and propagation distances are examined for crack in rail. The finite element method is utilized to model the rail with cracks and the results of experiment demonstrate the effectiveness of this model. Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of crack AE sources. The results illustrate that the intensity ratio among AE modes can identify the AE source types and the AE sources with different frequencies in rail. There are uniform AE mode features existing in the AE signals from AE sources in rail web, however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes. Different AE source types have the different propagation features in rail. It is helpful to understand the rail cracks and detect the rail cracks based on the AE technique.

Finite difference time domain analysis of two-dimensional surface acoustic wave piezoelectric phononic crystals at radio frequency

The finite-difference time-domain （FDTD） method is proposed for analyzing the surface acoustic wave （SAW） propagation in two-dimensional （2D） piezoelectric phononic crystals （PCs） at radio frequency （RF）, and also experiments are established to demonstrate its analysis result of the PCs＇ band gaps. The FDTD method takes the piezoelectric effect of PCs into account, in which periodic boundary conditions are used to decrease memory/time consumption and the perfectly matched layer boundary conditions are adopted as the SAW absorbers to attenuate artificial reflections. Two SAW delay lines are established with/without piezoelectric PCs located between interdigital transducers. By removing several echoes with window gating function in time domain, delay lines transmission function is achieved. The PCs＇ transmission functions and band gaps are obtained by comparing them in these two delay lines. When Aluminum/128°YX-LiNbO3 is adopted as scatter and substrate material, the PCs＇ band gap is calculated by this FDTD method and COMSOL respectively. Results show that computational results of FDTD agree well with experimental results and are better than that of COMSOL.

Acoustic signal analysis of underwater elastic cylinder

The echoes of underwater elastic cylinder comprise two types of acoustic components: Geometrical scattering waves and elastic scattering waves. The transfer function is appropriate to characterize the echo of targets. And the discrete wavelet transform of amplitude spectrum is presented and used to identify the resonant components of underwater targets.

Numerical analysis of the 2D acoustic field with fuzzy-random parameters

Regard for the fuzziness and the randomness in some acoustic fields,a method for the numerical analysis of the 2D acoustic field with Fuzzy-Random parameters was proposed based on the equivalent conversion of information entropy.In the proposed method,a fuzzyrandom acoustic field was treated as a pure fuzzy acoustic field or a pure random acoustic field by transforming all the variables into fuzzy variables or random variables.Perturbation finite element methods for analyzing the two-dimensional acoustic fuzzy and random field are deduced.The sound pressure response of a 2D acoustic tube and the 2D acoustic cavity of a car with fuzzy-random parameters were analyzed by the proposed method and the Monte Carlo method,the results show that the proposed method can be well applied to the numerical analysis of the 2D acoustic field with fuzzy-random parameters,and has good prospect of engineering application.