Measurement of loudspeaker mechanical impedance by changing the sound load at the throat of loudspeaker

A loudspeaker is a device that converts electrical energy into acoustic energy by coupling between electrical impedance, mechanical impedance, and radiation impedance. The loudspeaker electro-mechanical-acoustic coupling model provides the experimental feasibility to measure the characteristic parameters. In this paper, an economical and practical measurement method of loudspeaker mechanical impedance is proposed. First, the mathematical relationship between loudspeaker electrical impedance and mechanical impedance is obtained based on the loudspeaker electro-mechanical-acoustic coupling model. Second, two electrical impedances with different known radiation impedance are measured by using a developed measurement system. Finally, the real and imaginary parts of the mechanical impedance are obtained according to the mathematical relationship. This method neither assumes that the loudspeaker mechanical impedance is constant in a frequency band nor does it build FEM models based on structural parameters. A loudspeaker is measured by using a developed measurement system. The result shows that the mechanical impedance and the force factor are functions of frequency. Moreover, a radiation impedance measurement is performed to verify the feasibility and accuracy of the proposed method.

Hybrid Equivalent Circuit/Finite Element/Boundary Element Modeling for Effective Analysis of an Acoustic Transducer Array with Flexible Surrounding Structures

Transducer arrays are commonly analyzed by the finite element method (FEM) with high accuracy, but it is costly, particularly when having flexible surrounding structures. In this study, we developed an equivalent circuit (EC)-based model of an array of transducers with flexible surrounding structures for effective analysis. The impedance matrix was first constructed by coupling the electrical, mechanical impedance, and the acoustic radiation impedance obtained by the EC method and finite element-boundary element (FE-BE) coupling method. The transfer matrix of far-field pressure to the transducer response was then constructed by the FE-BE coupling method, and finally the sound pressure of the external acoustic field was obtained. To verify the accuracy, the results of the proposed method were compared with those of the conventional FEM. To evaluate the efficiency of the proposed method, the reduction in the degrees of freedom (DOFs) of the proposed method from the conventional FEM analysis was investigated. The simulation results of the proposed method are highly accurate and efficient. The proposed method is expected to be useful for conceptual design.

Selenium-Driven Enhancement of Synergistic Cancer Chemo-/radiotherapy by Targeting Nanotherapeutics

To overcome drug resistance in hypoxic tumors and the limitations of radiation impedance and radiation dose, we developed a nano-radiosensitizer to improve the efficacy of cancer radiotherapy. We used multifunctional...

Computation of the Alpha Cabin Sound Absorption Coefficient by Using the Finite Transfer Matrix Method (FTMM): Inter-Laboratory Test on Porous Media

The transfer matrix method (TMM) has become an established and widely used approach to compute the sound absorption coefficient of a multilayer structure. Due to the assumption made by this method of laterally infinite media, it is necessary to introduce in the computation the finite-size radiation impedance of the investigated system, in order to obtain an accurate prediction of the sound absorption coefficient within the entire frequency range of interest; this is generally referred to as finite transfer matrix method (FTMM). However, it has not been extensively investigated the possibility of using the FTMM to accurately approximate the sound absorption of flat porous samples experimentally determined in an Alpha Cabin, a small reverberation room employed in the automotive industry. To this purpose, a simulation-based round robin test was organized involving academic and private research groups. Four different systems constituted by five porous materials, whose properties were experimentally characterized, were considered. Each participant, provided with all the mechanical and physical properties of each medium, was requested to simulate the sound absorption coefficient with an arbitrary chosen code, based on the FTMM. The results indicated a good accuracy of the different formulations to determine the finite-size radiation impedance. However, its implementation in the computation of the sound absorption coefficient as well as the upper limit of the range of incidence angles within which the acoustic field is simulated, and the model adopted to describe each material, significantly influenced the results.

Approximation Model for Radiation Impedance of a Square Piston Source on an Infinite Planar Baffle

Approximation models based on a finite sum of Bessel functions of the first kind and a pair of simple rational transfer functions are proposed for radiation resistance and reactance of a square piston source mounted on an infinite planar baffle. Model accuracy is better than 1.6% for reactance and 0.5% for resistance within a very wide range of dimensionless frequency k√S (0.1–100). The very low and high frequency behaviors of radiation impedance are incorporated into the models' closed-form expressions so that the approximation error outside the specified frequency range tends to zero.

Weakly nonlinear oscillations of gas column driven by self-sustained sources

Self-sustained sources coupled to some sort of resonator have drawn attention recently as a subject of nonlinear dynamics with many practical applications as well as interesting mathematical problems from the chaos theory and the theory of synchronizations. In order to mimic the self-sustainability arising from physical background the van der Pol equation is commonly used as a model (e.g. vortex induced noise, flowstructure interactions, vocal folds motion etc.). In many cases the sound field inside the resonator is strong enough for weakly nonlinear formulation based on the Kuznetsov model equation to be employed. An array of sources governed by the inhomogeneous van der Pol equation coupled to the nonlinear acoustic wave equation is studied. The one dimensional constant cross-section open resonator with zero radiation impedance is assumed. The focus is on the main features such as mode-locking, harmonics generation and build-up from infinitesimal fluctuations.