Sound Pressure Response Research Articles

Theoretical modeling and parameter identification of balanced armature loudspeakers.

Theoretical modeling and parameter identification are essential for optimizing loudspeaker performance and enabling active control. Although relevant theories for moving-coil loudspeakers are well-developed, accurate theoretical modeling and parameter identification methods for balanced armature loudspeakers (BALs) are scant. This study proposes a model using the equivalent circuit method (ECM) for BALs, with consideration of the armature-suspension coupling as well as the non-piston vibration of the diaphragm. Based on the proposed ECM model, a time-domain identification algorithm utilizing measured voltage, current, and displacement data is established to identify the necessary parameters. Employing the theoretical model and proposed identification method, the model parameters of two different BALs are measured. Comparisons between experimental and numerical results demonstrate the accuracy and effectiveness of the proposed model and identification method in predicting impedance, displacement, and sound pressure responses.

Parameter identification and NVH characteristic analysis of automotive suspension rubber bushing

Accurate prediction of the dynamic stiffness of rubber bushings is crucial for optimizing vehicle vibration and noise performance. However, this task is highly challenging due to various influencing factors such as frequency and amplitude. Consequently, there has been limited research conducted in this area thus far. This paper presents a novel approach for predicting the dynamic stiffness of rubber bushings. The frequency and amplitude dependencies of rubber bushings were thoroughly investigated through dynamic loading tests. A comprehensive model for rubber bushings, incorporating parallel connections of elastic elements, friction elements, and higher-order fractional derivative viscous elements, was established. The model parameters were accurately identified using the GA-BP method. The results demonstrate that the proposed model exhibits a high level of precision in estimating dynamic stiffness across a frequency range of 0–200 Hz. In comparison to the conventional model, the proposed approach enables more precise computation of interior sound pressure response and enhances vehicle simulation accuracy.

Prediction of the sound pressure response in an enclosed cavity with sound absorbent walls using the CMA and AMA methods

The sound pressure response in an enclosed cavity with sound absorbent walls is predicted using the classical modal analysis (CMA) method and the asymptotic modal analysis (AMA) method. The sound absorbing material is represented as an equivalent fluid with frequency dependent bulk material properties. The equivalent fluid properties can be obtained from either impedance tube test data or based on micro-scale Biot material properties. In the low frequency range, the CMA method is implemented to include the frequency dependent material properties. In the medium and high frequency ranges, when modal density is high, the frequency dependence effects become cumbersome using CMA. The AMA method has been developed as an asymptotic extension of the CMA method for the mid- and high-frequency ranges and is extended here to incorporate the frequency dependence of an equivalent fluid properties of the sound absorbing materials. An enclosed rectangular box subjected to loudspeaker excitation is used to evaluate the effect of absorption materials using the CMA method for the low-frequency range and the AMA method for the mid- and high-frequency ranges. Test data have also been obtained for comparisons of the CMA method in the low frequency range. Using these procedures, the CMA and AMA methods can be applied to represent absorbent materials over a wide frequency range for enclosure architectural design.

Nonlinear analysis of flexoelectric acoustic energy harvesters with Helmholtz resonator

This paper presents a Helmholtz Resonator-type Flexoelectric Acoustic Energy Harvester (HR-FAEH), composed of a Helmholtz Resonator (HR) and a double-sided Flexoelectric Disk Oscillator (FDO). The electromechanical governing equations, incorporating geometric nonlinearity, are derived using Hamilton's principle. Utilizing the multiscale method, we obtain the cavity sound pressure, oscillator displacement, and voltage output response, with validation through simulations in COMSOL. The study's innovation lies in the concurrent consideration of piezoelectric and flexoelectric effects, enhancing the system's performance. The inclusion of geometric nonlinearity, accounting for large deformations, enhances the model's accuracy under high sound pressure excitations. Our research unveils performance degradation in the Helmholtz Resonator-type acoustic energy harvester under elevated environmental sound pressure. The combination of nonlinear analysis and structural optimization effectively mitigates this degradation. In comparison to the non-optimized harvester, the maximum voltage output increases by 39.1 %, and expressions for the optimized model parameters are provided. Additionally, we conduct parameter analyses for the HR and the FDO, elucidating the impact and optimal values of parameters such as film coverage radius and load resistance on system performance.

Uncertainty Quantification of Vibroacoustics with Deep Neural Networks and Catmull–Clark Subdivision Surfaces

This study proposes an uncertainty quantification method based on deep neural networks and Catmull–Clark subdivision surfaces for vibroacoustic problems. The deep neural networks are utilized as a surrogate model to efficiently generate samples for stochastic analysis. The training data are obtained from numerical simulation by coupling the isogeometric finite element method and the isogeometric boundary element method. In the simulation, the geometric models are constructed with Catmull–Clark subdivision surfaces, and meantime, the physical fields are discretized with the same spline functions as used in geometric modelling. Multiple deep neural networks are trained to predict the sound pressure response for various parameters with different numbers and dimensions in vibroacoustic problems. Numerical examples are provided to demonstrate the effectiveness of the proposed method.

Integrated near-infrared fiber-optic photoacoustic sensing demodulator for ultra-high sensitivity gas detection

An integrated near-infrared fiber-optic photoacoustic sensing demodulator was established for ultra-high sensitivity gas detection. The demodulator has capacities of interference spectrum acquisition and calculation, laser modulation control as well as digital lock-in amplification. FPGA was utilized to realize all the control and signal processing functions, which immensely improved the integration and stability of the system. The photoacoustic signal detection based on fiber-optic Fabry–Perot (F-P) acoustic sensor was realized by applying ultra-high resolution spectral demodulation technique. The detectable frequency of photoacoustic signal achieved 10 kHz. The system integrated lock-in amplification technology, which made the noise sound pressure and dynamic response range of sound pressure detection reached 3.7 μPa/√Hz @1 kHz and 142 dB, respectively. The trace C2H2 gas was tested with a multi-pass resonant photoacoustic cell. Ultra-high sensitivity gas detection was accomplished, which was based on high acoustic detection sensitivity and the matching digital lock-in amplification. The system detection limit and normalized noise equivalent absorption (NNEA) coefficient were reached 3.5 ppb and 6.7 × 10−10 cm−1WHz−1/2, respectively. The devised demodulator can be applied for long-distance gas measurement, which depends on the fact that both the near-infrared photoacoustic excitation light and the probe light employ optical fiber as transmission medium.

High‐Performance Sound Detection of Nanoscale‐Thick and Large‐Area Graphene Oxide Films in Liquids

This article presents nanoscale‐thick and large‐area graphene oxide (GO) films manufactured by a facile method to enable high‐performance sound detection in liquids. A Fabry–Perot (F–P) cavity consisting of a GO film, whose vibration diameter is ≈4.4 mm, and a single‐mode fiber (SMF) is used as the sensing core for sound detection in liquids. A sound‐transparent cap, consisting of a support sleeve and a sound‐transparent sleeve, is used to protect the GO‐sensing diaphragm to resist liquid pressure to enable long‐term stability. The sensing probes with GO diaphragms of ≈100 and 200 nm thickness are placed in ultra‐pure water for performance testing. Test results show that they maintain a linear sound pressure response, a flat frequency response, and a uniform directional response from 1 to 100 kHz. They have sensitivities of ≈630 mV Pa−1 and about 84 mV Pa−1, respectively, in the range of 1–100 kHz in all directions in different liquids. These results demonstrate the suitability of the nanoscale‐thick and large‐area GO films for sound detection in liquids with high performance.

Dual Fiber-Optic Microphone Based on Coherent Synthesis Technology

This paper proposes a dual fiber-optic microphone (DFOM) based on coherent synthesis technology, in which the sound pickup module mainly consists of two optical fibers and a reflection film, constituting two identical Fabry-Perot (FP) interferometric cavities as the acoustic sensing structure. The use of dual fiber-optic can increase the light intensity of the reflected light received by the photodetector (PD), while offsetting signal distortion caused by factors such as fiber length and temperature variations, and reducing signal interference, thereby improving the purity and accuracy of the signal. The DFOM exhibits strong fault tolerance, in case one of the optical fibers fails, the other one can still perform normal sound collection, thus enhancing the reliability of the microphone. Acoustic tests show that the sound pressure sensitivity of this DFOM at a frequency of 250 Hz is 64.8 mV/Pa. The signal-to-noise ratio (SNR) is as high as 62.45 dB under the action of a 6 kHz sound pressure signal. It maintains a linear sound pressure response and a flat frequency response in the range of 10 Hz to 20 kHz. These results indicate that the DFOM has high sensitivity and a wide frequency response range, making it suitable for acoustic detection within the audible range.

Radiation damping effect on the sound pressure response in a structural-acoustic cavity

A structural-acoustic system consisting of an enclosed cavity with flexible wall panels is considered to evaluate the effect of sound radiation-damping resulting from the panel vibration on the sound pressure level in the cavity. The interior cavity pressure can excite the flexible wall panels that will radiate noise to the exterior that in turn can reduce the interior noise due to the energy loss to the exterior surroundings. This energy loss is described as radiation damping of the interior cavity system. An enclosed rectangular cavity-plate system subjected to external random pressure excitation is used to evaluate the effect. The radiation damping is evaluated using a modal approach (FEM, BEM) to determine the radiation efficiency of the vibrating panels. The effect of the radiation damping for the example of a box-plate structure is evaluated using the CMA (classical modal analysis) method for the low-frequency range and the AMA (asymptotic modal analysis) method for the mid- and high-frequency ranges. The inclusion of radiation damping due to rigid body cavity mode excitation is shown to provide an improved prediction of the sound transmission loss especially in the low-frequency range.

Active control of interior road noise using the remote microphone technique

A multichannel feedforward headrest system for the active control of interior road noise in a vehicle cabin is built. The remote microphone technique is applied, which enables the estimation of the sound pressure responses at the passenger's ear positions without direct deployment of error microphones there. The optimal observation filter for the remote microphone technique is formulated in a so-called training stage using signals measured at two error microphones on the passenger's ears and an array of four to five monitoring microphones on the headrest, passenger seat and vehicle ceiling. The estimation accuracy of the observation filter is investigated through simulations and road test. Regarding the causality error encountered in a certain test case where the passenger leans forward, thus making the noise signals arrive at the monitoring microphones prior to the error ones, a delay factor is added into the original remote microphone technique to correctly compensate for the time delay. The noise attenuation performance of the active headrest system is then experimentally and subjectively determined, indicating a larger noise abatement in a wider spatial environment by applying the remote microphone technique.

Simulation analysis of instantaneous impact on the radiant syngas cooler by rapping vibrators

AbstractSlag or ash removal from water wall tubes in a radiant syngas cooler (RSC) is a routine task in operation, which can effectively increase the overall thermal efficiency. Rapping ash removal is one of the valid methods for shedding off the ash deposits in the high‐pressure surroundings of the RSC. In this study, the model of a real RSC was established by a numerical simulation based on the finite element software ABAQUS, and modal analysis and instantaneous response analysis (IRA) were researched to reveal the natural vibration characteristics of the RSC and aid the design of rapping ash removal. On the basis of the results of natural vibration characteristics and a subsequent harmony response, 16 Hz was set as the impact frequency, balancing off the vibrator number and the water‐tube displacement effect. It was indicated that ash deposit in the area around 1/2 longitudinal position was easy to remove due to great response to rapping action. Moreover, rapping at ½ position generally obtained greater displacement response in the whole RSC. A rapping design was proposed with six vibrators at the ½ longitudinal position and 16 Hz frequency, and then two rapping intervals were investigated comparatively. The case with a half‐cycle interval had a slightly larger response than the one‐cycle case, with a larger displacement in more circumferential tubes as well as with a greater sound pressure response in the RSC.

Panel Acoustic Contribution Analysis in Automotive Acoustics Using Discontinuous Isogeometric Boundary Element Method

In automotive industries, panel acoustic contribution analysis (PACA) is used to investigate the contributions of the body panels to the acoustic pressure at a certain point of interest. Currently, PACA is implemented mostly by either experiment-based methods or traditional numerical methods. However, these schemes are effort-consuming and inefficient in solving engineering problems, thereby restraining the further development of PACA in automotive acoustics. In this work, we propose a PACA scheme using discontinuous isogeometric boundary element method (IGABEM) to build an easily implementable and efficient method to identify the relative acoustic contributions of each automotive body panel. Discontinuous IGABEM is more accurate and converges faster than continuous BEM and IGABEM in the interior sound pressure evaluation of automotive compartments. In this work, a contribution ratio is defined to estimate the relative acoustic contribution of the structure panels; it can be calculated by reusing the coefficient matrix that has already been generated in the sound pressure evaluation process. The utilization of the parallel technique enables the proposed method to be more efficient than conventional methods; it is validated in two numerical examples, including a car passenger compartment subjected to realistic boundary conditions. A sound pressure response experiment based on a steel box is conducted to verify the accuracy of the interior sound pressure calculation using discontinuous IGABEM. This work is expected to promote the practical process of IGABEM for application in automotive acoustic problems.

Acoustic field characteristic analysis of the rotary acoustic cavity coupled system

The rotary acoustic cavity coupled system can be generated in working conditions of aviation, aerospace, ship, machinery, and other fields. The rotary acoustic cavity includes cylindrical, spherical, and conical acoustic cavities, which integrates into the unified analysis model by iso-parametric transformation in finite element method. To study the acoustic field characteristic of rotary acoustic cavity coupled system, a unified analysis model of rotary acoustic cavity coupled system is established: First, the acoustic field characteristic of the coupled system is researched by improved Fourier series method, and the admissible sound pressure function is constructed by three-dimensional modified Fourier series. Then, the acoustic field domain energy functional is established, and the coupled domain energy functional including the coupled potential energy between the sound cavities is introduced to acquire the total energy functional of the coupled system. Finally, the energy equation is solved by Rayleigh–Ritz method, and the natural frequency and corresponding mode of the coupled system are obtained. The unified analysis model demonstrates excellent convergence and accuracy, which is verified by the results of finite element method. Sound pressure responses of the coupled system are obtained by introducing the internal point sound source excitation. The effect of relevant parameters of the coupled system on natural frequency and sound pressure response is investigated, which can provide theoretical guidance for vibration and noise reduction.

Vibro-acoustic characteristics analysis of the rotary composite plate and conical–cylindrical double cavities coupled system

PurposeThe purpose of the study is to obtain and analyze vibro-acoustic characteristics.Design/methodology/approachA unified analysis model for the rotary composite laminated plate and conical–cylindrical double cavities coupled system is established. The related parameters of the unified model are determined by isoparametric transformation. The modified Fourier series are applied to construct the admissible displacement function and the sound pressure tolerance function of the coupled systems. The energy functional of the structure domain and acoustic field domain is established, respectively, and the structure–acoustic coupling potential energy is introduced to obtain the energy functional. Rayleigh–Ritz method was used to solve the energy functional.FindingsThe displacement and sound pressure response of the coupled systems are acquired by introducing the internal point sound source excitation, and the influence of relevant parameters of the coupled systems is researched. Through research, it is found that the impedance wall can reduce the amplitude of the sound pressure response and suppress the resonance of the coupled systems. Besides, the composite laminated plate has a good noise reduction effect.Originality/valueThis study can provide the theoretical guidance for vibration and noise reduction.

Interval Analysis of Interior Acoustic Field with Element-By-Element-Based Interval Finite-Element Method

This paper presents an element-by-element-based interval finite-element method (EBE-IFEM) for the uncertain interior acoustic field prediction with uncertain-but-bounded parameters. The interval dynamic matrices and loads vectors are assembled with the element-by-element (EBE) strategy, and decomposed into diagonalization forms additionally. Then the interval dynamic equation can be rewritten as iterative enclosure form, and finally are analyzed by both Rump’s method and the Neumaier-Pownuk method in the comparative discussion. Meanwhile, numerical examples are calculated with the interval perturbation finite-element method (IPFEM), modified interval finite-element method (MIPFEM), and Monte Carlo simulation. The numerical results demonstrate that the solution by the EBE-IFEM shows more accurate and more stable than other cross-references, when evaluating the intervals of sound pressure response in interior acoustic field.

Robust prediction metrics for structure-borne noise in timber buildings

This paper presents an investigation of prediction metrics for structure-borne noise in timber buildings, based on the vibration response of the structure. The purpose of the study is to derive a robust measure for predicting structure-borne noise in timber buildings based solely on the vibration response; a measure with a known correlation to the actual acoustic response. Such a measure is useful for establishing simplified numerical prediction models, and for making robust assessments of different design alternatives. The procedure has previously been applied to automotive applications with a valuable outcome for the industry. The vibration and sound pressure responses in a room of a multi-storey building are calculated using the finite element method. As excitation, a harmonic unit point load (20-300 Hz) located at another storey of the building is used. Based on the structural and acoustic response fields, scalar values are calculated by performing spatial and frequency domain averaging and summations. Various methods for calculating scalar values from the vibration response are investigated. The correlation between the vibration scalar values and the acoustic scalar values are presented.

Theoretical Modeling of Piezoelectric Cantilever MEMS Loudspeakers

Piezoelectric microelectromechanical system (MEMS) loudspeakers have received extensive attention in recent years. In particular, the piezoelectric cantilever MEMS loudspeaker, which uses multilayer piezoelectric cantilever actuators (MPCAs), has attracted attention because of its small size, low cost, ease of manufacture, and desirable piston movement. However, owing to the complex driving principles of MPCAs, no adequately efficient and appropriate method currently exists that can be used to analyze and predict the performance of piezoelectric cantilever MEMS loudspeakers. In this study, the equivalent circuit method (ECM) is adopted to theoretically model piezoelectric cantilever MEMS loudspeakers, and an ECM model with a special MPCA transformer for electromechanical conversion is proposed. With the proposed ECM model, the performance characteristics of piezoelectric cantilever MEMS loudspeakers, such as the displacement and sound pressure response, can be calculated efficiently and conveniently. To verify the accuracy of the ECM model, the finite element method is adopted for simulation, and the simulated results are compared with those of the ECM models. A satisfactory agreement was found, which verifies the accuracy of the proposed ECM model.

Research on the Manufacturing Quality of Co-Cured Hat-Stiffened Composite Structure.

The stringer-stiffened structure is widely used due to its excellent mechanical properties. Improving the manufacturing quality of stringer-stiffened structure which have complex geometry is important to ensure the bearing capacity of aviation components. Herein, composite hat-stiffened composite structures were manufactured by different filling forms and bladders with various properties, the deformation of silicone rubber bladder in co-curing process was studied by using the finite element method. The thickness measurement at different positions of the hat-stiffened structure was performed to determine the best filling form and bladder property. Moreover, in view of the detection difficulties in R-zone of stringer, numerical simulation was performed to get the sound pressure and impulse response of at the R-zone of stringer by Rayleigh integration method, and an effective equipment which could stably detect the manufacturing quality of R-zone was designed to verify the correctness of sound field simulation and realize the detection of stringer. With the optimum filling form and bladder properties, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process.

Research on the selection and layout of the cantilever sensor based on photoacoustic spectroscopy gas detection technology

Gas detection has become an indispensable part of the power equipment maintenance. Because of many advantages, cantilever enhanced photoacoustic(PA) spectroscopy was studied by many researchers. In this paper, with the help of Finite Element Method (FEM) simulations with the commercial software COMSOL, we have analyzed the distribution of the sound pressure inside the gas cell, in addition, we have analyzed the relationship between the Young’s modulus and size of the cantilever beam and its deformation, the relationship between the cantilever size and its eigen-frequencies were also obtained. Besides, we have performed the experiment of the deformation measurement. The results show that: for the gas cell, when it works at the first order resonance frequency, the maximum value of the sound pressure appears at the geometric center. For the main resonance cavity, with its length and radius increase, the first order resonance frequency of the gas cell decreases. Under the condition of ideal linear sound source, as the length and radius of the main resonance cavity changes, in the frequency domain, the sound pressure response curve changes, the maximum sound pressure corresponds the PA cell with 85 mm in length and 2 mm in radius. For the cantilever beam, with the increase of the Young’s modulus, the deformation decreases. The deformation is proportional to the fourth power of the length, whereas it is inversely proportional to the width and inversely proportional to the third power of the thickness. However, the experimental results showed that there may be a deviation in the vibration measurements by the vibration meter. As for the first order eigen-frequency, it is negatively correlated with the length and positively correlated with the thickness, but independent of the width. With the increase of the distance between the sound source and the cantilever beam, the deformation decreases.

Moment-Based Hybrid Polynomial Chaos Method for Interval and Random Uncertain Analysis of Periodical Composite Structural-Acoustic System with Multi-Scale Parameters

An interval and random moment-based arbitrary polynomial chaos method (IRMAPCM) is proposed in this paper for the analysis of periodical composite structural-acoustic systems with multi-scale uncertain-but-bounded parameters. In IRMAPCM, the response of structural-acoustic system is approximated as moment-based arbitrary polynomial chaos (maPC) expansion. IRMAPCM can construct the polynomial basis according to the moment of the random variable without knowing the Probability Density Function (PDF), which can avoid the errors introduced by estimating the PDF. Numerical examples of a hexahedral box and an automobile passenger compartment are given to investigate the effectiveness of IRMAPCM for the prediction of the sound pressure response of structural-acoustic systems.