Acoustic Elements Research Articles

Enhanced modal matching formulation for a cost-efficient computation of the acoustical properties of multi-layer perforated and micro-perforated partitions

As rigidly backed micro-perforated panels (MPPs) are Helmholtz-type absorbers, their performance is typically limited to narrow frequency bands. The use of multi-layer or multi-array partitions has been widely studied to extend their absorption over a broader range. Optimal selection often requires combination of macro and micro-perforated panels constitutive of the overall partition. However, it is difficult to find a unified impedance model that may account for the whole range of hole diameters variations encountered in an optimization process. In this study, an enhanced multi-modal (EMM) formulation is developed that overcomes limitations for the domain of validity of the MPP parameters. It provides a unit cell transfer impedance that accounts for visco-thermal dissipation and high-order evanescent modes both within the perforation and at the panel walls. It can be used as a Robin-type visco-thermal boundary condition in a pure Acoustic finite element model (FEM) of a complex micro-/macro-perforated structure. This approach leads to a mixed analytical-numerical approach with a much lower computational cost than a full visco-thermal Acoustic FEM model. The inclusion of hole or panel interaction effects is then achieved through the acoustic or structural FEM parts.

The Mechanics of Social Interactions Between Cats and Their Owners.

This is a mini review that summarizes what is known from quantitative observational studies of social interactions between domestic cats and humans in both laboratory colonies and the home setting. Only results from data that have been statistically analyzed are included; hypotheses still to be tested will be declared as such. In some cases, the observational data have been combined with independently collected subjective assessments by the owners of the animals' character and owner personality traits to help interpret the data. Further some relevant experimental studies are also included. All social interactions between cats and humans that are discussed below assume that the animals were socialized to people as kittens, the first topic of this review. Such socialized cats show what might be called “friendliness to humans,” which in turn affects human attachment to the cat. The visual and acoustic behavioral elements used to communicate and interact with other cats can be perceived by people and are also employed by the cats when interacting with them. The initiation, and the initiator of social interactions between cats and humans have been shown to influence both the duration of the interaction bout and total interaction time in the relationship. Compliance with the interactional “wishes” of the partner is positively correlated between the cats and the humans over all human-cat dyads examined. Cats do not spontaneously prefer one gender or age cohort of people, but the humans in those cohorts behave differently to the cats causing the latter to react differentially. The dyadic interaction structure has also been shown to differ between women and men and between older and younger adults. Nevertheless, cats—merely their presence but of course their behavior—can affect human moods and human mood differences have been shown to affect the behavior of the cats. Finally, differences have been found between interactions with purebred and non-purebred cats and between younger and older cats.

A Strategy to Tune Acoustic Terminations of Single-Can Test-Rigs to Mimic Thermoacoustic Behavior of a Full Engine

Abstract Thermoacoustic properties of can-annular combustors are commonly investigated by means of single-can test-rigs. To obtain representative results, it is crucial to mimic can–can coupling present in the full engine. However, current approaches either lack a solid theoretical foundation or are not practicable for high-pressure rigs. In this study, we employ Bloch-wave theory to derive reflection coefficients that correctly represent can–can coupling. We propose a strategy to impose such reflection coefficients at the acoustic terminations of a single-can test-rig by installing passive acoustic elements, namely straight ducts or Helmholtz resonators. In an iterative process, these elements are adapted to match the reflection coefficients for the dominant frequencies of the full engine. The strategy is demonstrated with a network model of a generic can-annular combustor and a three-dimensional (3D) model of a realistic can-annular combustor configuration. For the latter, we show that can–can coupling via the compressor exit plenum is negligible for frequencies sufficiently far away from plenum eigenfrequencies. Without utilizing previous knowledge of relevant frequencies or flame dynamics, the test-rig models are adapted within a few iterations and match the full engine with good accuracy. Using Helmholtz resonators for test-rig adaption turns out to be more viable than using straight ducts.

Modeling Noise Radiation From Concrete Box Girder Bridges as an Infinitely Long Periodic Structure Excited by a High-Speed Train

Abstract Concrete box girder bridges occupy over 80% of the total mileage of the Chinese high-speed railway. The box girder structure has many natural modes of low frequencies, which can be excited by a train passing at high-speed, generating low-frequency bridge noise. This paper is concerned with the prediction of such bridge noise and reports a prediction model. The model, as other existing models of the same nature, also incorporates two parts, one dealing with vehicle–track-viaduct dynamics and the other dealing with sound radiation from the girders, but takes into account more features related to high-speed. In this model, vehicle–track-viaduct dynamics is dealt with in the frequency-domain based on the theory of infinitely long periodic structure and the Fourier-series method, predicting vibration frequency spectra for each and every box girder. The predicted vibration frequency spectra of all the box girders are expressed as a sum of propagating waves at different wavenumbers, and sound radiation from each propagating wave is evaluated using the 2.5D acoustic boundary element method. This approach to sound radiation enables contributions from all the box girders to be included at a reasonable computational cost. This paper continues with a comparison in bridge vibration and noise between prediction and measurement for a typical site. And finally, based on the parameters of that site, characteristics of noise radiation from the concrete box girders are studied using the prediction model.

Prediction of vibration radiation noise from shell of straw crushing machine

In order to predict the radiation noise of the vibrating shell of the straw crusher in the design phase, the computational fluid dynamics–discrete element coupling method is initially used to simulate the airflow–straw coupled flow field in the straw crusher, and the pulsating pressure generated by the coupled flow field is applied to the inner surface of the shell of the crusher. Then, the harmonic response of the shell is analyzed, and its results are used to be the acoustic boundary condition. Finally, the finite element and acoustic boundary element combined test methods are used to predict vibration noise of the straw crusher shell. The results indicate that the produced vibration noise of the straw crusher shell changes as the excitation frequency of the rotor rotation changes. The maximum vibration noise is achieved at the excitation fundamental frequency, and radiation noises at the harmonic frequencies decrease as the frequency increases. The simulated value of the sound pressure level of each measuring point at the excitation fundamental frequency and harmonic frequencies is basically the same as those of the experiment. Moreover, it is found that the maximum difference between the simulated and experimental value of measuring points is 1.69 dB(A). Therefore, it is concluded that the numerical model of the vibration radiation noise is accurate. The vibration noise of the shell at the inlet is the largest, and the main noise source of the vibration radiation noise is the dipole sound source of the rotating hammer rotor. The corresponding design method provides the reference for the low-noise design of straw crushers.

Wideband Hybrid Monolithic Lithium Niobate Acoustic Filter in the K-Band.

This article presents the design approach and the first demonstration of a wideband hybrid monolithic acoustic filter in the K -band, which exceeds the limitation of electromechanical coupling on the fractional bandwidth (FBW) of acoustic filters. The hybrid filter utilizes the codesign of electromagnetic (EM) and acoustic to attain wide bandwidth while keeping the advantages of small sizes and high Q in the acoustic domain. The performance trade space and design flow of the hybrid filter are also presented in this article, which allows this technology to be applied for filters with different center frequencies and FBWs. The hybrid filter is simulated by hybridizing the EM and acoustic finite element analysis, which are carried out separately and combined at a system level. The fabricated filter built with resonators having an electromechanical coupling of 0.7% based on the seventh-order antisymmetric Lamb wave mode (A7) has a 3-dB FBW of 2.4% at 19 GHz and a compact footprint of 1.4 mm2.

Superiorized Photo-Acoustic Non-NEgative Reconstruction (SPANNER) for Clinical Photoacoustic Imaging.

Photoacoustic (PA) imaging can revolutionize medical ultrasound by augmenting it with molecular information. However, clinical translation of PA imaging remains a challenge due to the limited viewing angles and imaging depth. Described here is a new robust algorithm called Superiorized Photo-Acoustic Non-NEgative Reconstruction (SPANNER), designed to reconstruct PA images in real-time and to address the artifacts associated with limited viewing angles and imaging depth. The method utilizes precise forward modeling of the PA propagation and reception of signals while accounting for the effects of acoustic absorption, element size, shape, and sensitivity, as well as the transducer's impulse response and directivity pattern. A fast superiorized conjugate gradient algorithm is used for inversion. SPANNER is compared to three reconstruction algorithms: delay-and-sum (DAS), universal back-projection (UBP), and model-based reconstruction (MBR). All four algorithms are applied to both simulations and experimental data acquired from tissue-mimicking phantoms, ex vivo tissue samples, and in vivo imaging of the prostates in patients. Simulations and phantom experiments highlight the ability of SPANNER to improve contrast to background ratio by up to 20 dB compared to all other algorithms, as well as a 3-fold increase in axial resolution compared to DAS and UBP. Applying SPANNER on contrast-enhanced PA images acquired from prostate cancer patients yielded a statistically significant difference before and after contrast agent administration, while the other three image reconstruction methods did not, thus highlighting SPANNER's performance in differentiating intrinsic from extrinsic PA signals and its ability to quantify PA signals from the contrast agent more accurately.

Efficient Theoretical and Numerical Methods for Solving Free Vibrations and Transient Responses of a Circular Plate Coupled With Fluid Subjected to Impact Loadings

Abstract This paper presents an easy-to-use theoretical method and an efficient numerical method for solving free vibrations and transient responses of a circular plate coupled with fluid subjected to impact loadings and provides insights into various coupling cases with these developed methods. The Kirchhoff plate theory, Mindlin–Reissner plate theory, and the linear velocity potential function are used. The wet mode of the coupled system is described as the superposition of dry modes of the plate, which has been considered in few studies. The natural frequencies and corresponding mode shapes are solved using the orthogonality of dry modes. The transient responses of the plate are then solved using the superposition of the wet modes and the orthogonality of dry modes. To validate the theoretical results, an efficient and flexible finite element method is proposed and verified by comparing with commercial software. The four-node mixed interpolation of the tensorial component quadrilateral plate finite element (MITC4) and the eight-node acoustic pressure element are used to model the plate and the fluid, respectively. The theoretical and numerical methods provide reliable and accurate results. Parametric studies are performed to investigate the influence of geometric sizes, plate material properties, and fluid properties on the natural frequencies of the coupled system. A coupling parameter of fluid–structure interaction is proposed. The nondimensional added virtual mass incremental (NAVMI) factor decreases as the coupling parameter increases. Besides, the influence of fluid on wet modes of the plate decreases with the order.

Unsteady propulsion and the acoustic signature of undulatory swimmers in and out of ground effect

Propulsive performance and acoustic emission of undulatory swimmers are investigated using an integrated unsteady potential flow and acoustic boundary element solver. Anguilliform and carangiform swimming gaits are modeled by a deforming NACA 0012 airfoil section. The effect of a ground plane on undulatory swimming and associated noise generation is examined as a function of reduced frequency and above plane altitude with the method of images. Ground effect becomes pronounced when swimming within half of a chord length from the ground plane, where the thrust, power, propulsive efficiency, and peak acoustic pressure all increase for both gaits.

Rufous horneros perceive and alter temporal coordination of duets during territorial interactions

Temporal coordination of duets consists of nonrandom overlap, alternation or association between rhythms of acoustic elements. Since duet coordination presumably requires high attentiveness between signallers, the coalition quality hypothesis suggests it may indicate the ability or motivation of partners to engage cooperatively in aggressive interactions against intruders. To test this hypothesis, we monitored behavioural as well as vocal responses in a playback experiment conducted with a polyphonal duetting bird, the rufous hornero, Furnarius rufus . We used three categories of treatments in the experiment, which totalled six treatments: duet playbacks that varied in phrase overlap and coordination of temporal rhythms; nonoverlapped (consecutive) solos; and a control heterospecific song. We predicted that birds would respond more strongly to playbacks of coordinated duets than to uncoordinated duets, and also to playbacks of uncoordinated duets than to nonoverlapping male and female solo songs. Coordinated duets (degree of phrase overlap) provoked the weakest response across conspecific stimuli, whereas the responses to uncoordinated duets and nonoverlapped solos were similar. However, partners produced more highly coordinated duets (degree of phrase overlap) in response to coordinated duets (association of phrase rhythms), when compared to all other stimuli. These results suggest that territorial pairs not only perceive but also alter their degree of temporal coordination of duets during territorial interactions. In addition, partners seem to behave cautiously and with more coordinated duets when responding to paired intruders that produce coordinated duets. Our results partially support the coalition quality hypothesis, suggesting that duet coordination may indicate the ability of partners to cooperatively engage in aggressive interactions. • Rufous horneros were exposed to playbacks of duets varying in temporal coordination. • Coordinated duets provoked the weakest response from birds. • However, partners increased duet coordination in response to coordinated duets. • Results suggest that highly coordinated duets may be intimidating to individual birds.

Acoustic simulation of ultrasonic testing and neural network used for diameter prediction of three-sheet spot welded joints

• Extraction of mathematical formulas for diameter calculation of spot-welded joints. • Acoustic finite element simulation of Ultrasonic Testing (UT) on three-sheet spot welds. • Utilization of a Multilayer Perceptron (MLP) artificial neural network for the prediction of nugget diameters. • Quantitative comparison of theoretical, numerical and experimental results of ultrasonic testing. • An approach to automatically pass or reject spot welds using an inspection technique based on diameter estimation. Ultrasonic Testing (UT) is one of the most common types of nondestructive methods that is being used in various industries, especially in the automotive industry. In this paper, qualitative and quantitative control of resistance spot welds on three-sheet joints was studied. Initially, mathematical model of ultrasonic waves was extracted for triple sheet joints. Then, acoustic simulation of ultrasonic testing on spot welds was performed using Finite Element Method (FEM). Afterwards, A Multilayer Perceptron (MLP) neural network was used to classify spot welds based on their diameter. There was a mean error of 20.9 % between peak amplitudes of numerical and theoretical models which the most reason was due to the dispersion effect. Also, theoretical formula for diameter calculation showed 14 % error. Results of Artificial Neural Network (ANN) had an error of 5.11 % on average which indicated capability of ANN to evaluate quality of spot welds. It was also found that diameter calculation using mathematical formulas are less accurate than estimation by ANN. Finally, the simulation and UT results of real samples were compared which indicated that ANN has over 90 % accuracy in identifying the state of spot welds.

Acoustic-vibration analysis of the gear-bearing-housing coupled system

Aiming to solve the problem of noise generated by running gearbox, a computing method was proposed for predicting the noise of a gearbox from steady dynamic response to the acoustic radiation calculation. Vibrations, generated during gear meshing process, were transmitted to the bearing through the shafting. Then vibrations were transmitted to the housing, caused the vibration of housing. The vibration noise of housing was the main source of gearbox noise. Firstly, a dynamics model of the gear-rotor-bearing system was established. A dynamic bearing force was calculated by using this model, which was taken as the excitation force for the gearbox. Then, a housing finite element model was constructed, and the housing surface velocities excited by the dynamic bearing forces were obtained. Finally, an acoustic model was established using the acoustic boundary element method to predict the noise distribution of the gearbox, and the effects of meshing excitation on vibration and noise of the gearbox were found. An experimental bench was built to measure the vibration and noise of the gearbox, which verified the accuracy of the simulation results. This study was based on the overall methodology that could provide ideas for the gearbox optimized design.

Guinea pig's courtship call: cues for identity and male dominance status?

Reproduction involves communication. Males usually evolve elaborate displays that may declare their qualities and attract females to mate, using signals from different modalities. Females may use cues encoded in courtship signals to evaluate males and make choices concerning their qualities. We investigated the acoustic element of the elaborate display of the small Cavia rodents, the guinea pigs, Cavia porcellus . We verified the potentiality of the courtship call (purr) to reflect male identity and social status, through variations in acoustic structure and male vocal performance. Our results suggest that the purr encodes individuality but not male dominance status. Vocal performance and purr's structural parameters differed between individuals, but there was no correlation between acoustic parameters and male dominance status. Courtship in cavies is a multimodal display, and male quality may be encoded in visual and chemical signals. This study is the first evidence of individuality in the purr. Further studies may reveal the role of each communication channel in the courting process of Cavia . • Male guinea pigs perform an elaborate courtship, including a vocalization (purr). • We examined whether purr acoustic structure encodes identity or social status. • Purr encodes individuality, but not male dominance status. • Male quality may be encoded in visual and chemical signals.

Marine soundscape variation reveals insights into baleen whales and their environment: a case study in central New Zealand.

Baleen whales reliably produce stereotyped vocalizations, enabling their spatio-temporal distributions to be inferred from acoustic detections. Soundscape analysis provides an integrated approach whereby vocal species, such as baleen whales, are sampled holistically with other acoustic contributors to their environment. Acoustic elements that occur concurrently in space, time and/or frequency can indicate overlaps between free-ranging species and potential stressors. Such information can inform risk assessment framework models. Here, we demonstrate the utility of soundscape monitoring in central New Zealand, an area of high cetacean diversity where potential threats are poorly understood. Pygmy blue whale calls were abundant in the South Taranaki Bight (STB) throughout recording periods and were also detected near Kaikōura during autumn. Humpback, Antarctic blue and Antarctic minke whales were detected in winter and spring, during migration. Wind, rain, tidal and wave activity increased ambient sound levels in both deep- and shallow-water environments across a broad range of frequencies, including those used by baleen whales, and sound from shipping, seismic surveys and earthquakes overlapped in time, space and frequency with whale calls. The results highlight the feasibility of soundscape analysis to quantify and understand potential stressors to free-ranging species, which is essential for conservation and management decisions.

Sensitivity analysis of acoustic eigenfrequencies by using a boundary element method.

This paper presents a boundary element-based scheme for the sensitivity analysis of acoustic eigenfrequencies of both interior and exterior acoustic systems. The nonlinear eigenvalue problem generated by the acoustic boundary element method is first reformulated into a generalized eigenvalue problem of reduced dimension through a contour integral approach. The sensitivity formulations for acoustic eigenfrequencies are then derived based on an adjoint method that uses both the right and left eigenvectors. The adaptive cross approximation in conjunction with the hierarchical matrices is used to reduce the solution burden of the boundary element systems. The Burton-Miller-type combined formulation is applied to shift the spurious eigenfrequencies and their sensitivities, and the strategies to identify the spurious results are suggested. Three numerical examples are used to verify the accuracy and applicability of the developed scheme.

Global Acoustic Impedance for the Analysis of Acoustic Scattering From Elastic Structures

The interaction between the sound field outside an elastic structure and its boundary is of paramount importance in the field of acoustics. This paper describes the global acoustic impedance in the form of impedance integral operator and impedance matrix for the analysis of elastic structures. In general, the excitation applied locally to the structure can induce vibration on the entire structure surface and hence the global acoustic impedance is introduced to characterize the relationship between the resultant sound pressure and acoustic particle velocity. The main advantage of the global acoustic impedance over the local acoustic impedance is that it facilitates improved physical insights into the sound field due to the presence of excitation sources. Furthermore, the acoustic impedance of an elastic spherical shell in matrix form is solved and analyzed by solving the finite element equation of structural dynamics with programming techniques. The impedance matrix is subsequently taken as the boundary condition to investigate the acoustic scattering from the elastic shell structure using the acoustic boundary element method. Explanations for the difference between the acoustic scatterings calculated based on the global acoustic impedance and the local acoustic impedance are offered.

Улучшение акустических характеристик пневмомеханизмов машин контактной сварки

Welding production forms the basis of assembly production in many branches of industry. Welding equipment is the most numerous in the environment of assembly of transport engineering units. This equipment is used both at the initial stage of assembly operations and at the final stage. The most common machines are single-point and multi-point welding with pneumatic drive. Traditional disadvantage of welding machines using pneumatic drives is the presence of intense acoustic flows at the outlet of the energy carrier, the operating sound level of which significantly exceeds the established sanitary norms and worsens personnel working conditions. Among the sources of aerodynamic flows in contact welding machines, the most relevant noise is during technological release of energy from the pneumatic mechanisms of the welding machines control systems, including the existing fleet of contact welding machines. Standard noise mufflers in the contact welding machines, the acoustic elements of which are made in the form of porous metal bushings or pots, are working efficiently for a short period of time up to 200 hours, both domestic and foreign companies Festo, Camozzi, Pneumax. The reason is that when pulsed, technological release of compressed air containing oil particles, in the presence of external dust sources, the channels of porous sound-absorbing elements are clogged with a suspension of oil with the above specified particles and condensate. This leads to an increase in the hydraulic resistance of the muffler path, an increase in the back pressure in the silencing chamber, and, as a result, to the destruction of the acoustic element, which requires frequent replacement of the muffler. The results are presented concerning the development of new chamber mufflers for contact welding machines, which efficiently reduce noise, operate without maintenance for more than fifteen years without requiring replacement. They are recommended for various branches of industries operating pneumatic systems for various purposes.

Training the Vocal Expression of Emotions in Singing: Effects of Including Acoustic Research-Based Elements in the Regular Singing Training of Acting Students

This study examines the effects of including acoustic research-based elements of the vocal expression of emotions in the singing lessons of acting students during a seven-week teaching period. This information may be useful in improving the training of interpretation in singing. Experimental comparative study. Six acting students participated in seven weeks of extra training concerning voice quality in the expression of emotions in singing. Song samples were recorded before and after the training. A control group of six acting students were recorded twice within a seven-week period, during which they participated in ordinary training. All participants sang on the vowel [a:] and on a longer phrase expressing anger, sadness, joy, tenderness, and neutral states. The vowel and phrase samples were evaluated by 34 listeners for the perceived emotion. Additionally, the vowel samples were analyzed for formant frequencies (F1-F4), sound pressure level (SPL), spectral structure (Alpha ratio=SPL 1500-5000 Hz - SPL 50-1500 Hz), harmonic-to-noise ratio (HNR), and perturbation (jitter, shimmer). The number of correctly perceived expressions improved in the test group's vowel samples, while no significant change was observed in the control group. The overall recognition was higher for the phrases than for the vowel samples. Of the acoustic parameters, F1 and SPL significantly differentiated emotions in both groups, and HNR specifically differentiated emotions in the test group. The Alpha ratio was found to statistically significantly differentiate emotion expression after training. The expression of emotion in the singing voice improved after seven weeks of voice quality training. The F1, SPL, Alpha ratio, and HNR differentiated emotional expression. The variation in acoustic parameters became wider after training. Similar changes were not observed after seven weeks of ordinary voice training.

Усовершенствованный резонатор Гельмгольца

The three-dimensional acoustic finite element method is used to predict the transmission loss of the Helmholtz resonance muffler. The results are in good agreement with the experimental results, indicating the applicability and accuracy of the numerical method used in this paper. On the one hand, in order to reduce the resonance frequency without changing the shape of the resonator, the connecting tube is extended to the inside of the resonator, and the influence of the extension length and the cross section shape of the extension tube on the acoustic characteristics of the resonator is discussed in detail. On the other hand, in order to broaden the muffled frequency band of the traditional Helmholtz resonators, the resonators are combined in series and parallel, and the influence of the combined structure on the acoustic characteristics is discussed in detail.

The influences of auditory cues and individual differences on the processing of musical tension

<p id="C2">The pattern of tension-relaxation is an essential component in music. Musical tension, building a bridge between objective sound and subjective experience, is important for the generation of musical emotion. On the one hand, musical tension is influenced by acoustic elements and structural organizations of tonal hierarchy, which is supported by theoretic models and empirical studies. On the other hand, musical tension experienced by listeners is also affected by individual differences, such as cultural background and musical ability. Future studies should pay more attention to musical tension induced by temporal structure and large-scale tonal structure. Meanwhile, the mechanism of tension induction also needs to be examined, which will be helpful to deepen our understanding of tension and emotion processing in music.