scholarly journals Analysis and Identification of Nonlinear Acoustic Damping in Miniature Loudspeakers

2021 ◽  
Vol 11 (16) ◽  
pp. 7713
Author(s):  
Jie Huang ◽  
Ke-Yu Pan ◽  
Xue-Lei Feng ◽  
Yong Shen
Keyword(s):  
Theoretical Calculations ◽  
Nonlinear System Identification ◽  
Equivalent Circuit Model ◽  
High Amplitude ◽  
Air Velocity ◽  
Acoustic Damping ◽  
Nonlinear Acoustic ◽  
Standing Wave Tube ◽  
Impedance Tube Method ◽  
Electrical Data

Nonlinear acoustic damping is a key nonlinearity in miniature loudspeakers when the air velocity is at a high amplitude. Measurement of nonlinear acoustic damping is beneficial for predicting and analyzing the performance of miniature loudspeakers. However, the general measuring methods for acoustic impedance, such as the standing-wave tube method or the impedance tube method, are not applicable in this scenario because the nonlinear acoustic damping in miniature loudspeakers is coupled with other system nonlinearities. In this study, a measurement method based on nonlinear system identification was constructed to address this issue. The nonlinear acoustic damping was first theoretically analyzed and then coupled in an equivalent circuit model (ECM) to describe the full dynamics of miniature loudspeakers. Based on the ECM model, the nonlinear acoustic damping was identified using measured electrical data and compared with theoretical calculations. The satisfactory agreement between the identification and theoretical calculations confirms the validity of the proposed identification method.

Semiautomated suppression of above-surface diffractions in GPR data

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. J43-J50 ◽  
Author(s):  
Stefan F. Carpentier ◽  
Heinrich Horstmeyer ◽  
Alan G. Green ◽  
Joseph Doetsch ◽  
Ilaria Coscia
Keyword(s):  
Ground Penetrating Radar ◽  
Synthetic Data ◽  
Complete Removal ◽  
Original Data ◽  
High Amplitude ◽  
Air Velocity ◽  
Efficient Suppression ◽  
Useful Signal ◽  
Multichannel Filtering ◽  
Ground Penetrating

Diffractions from above-surface objects can be a major problem in the processing and interpretation of ground-penetrating radar (GPR) data. Whereas methods to reduce random and many other types of source-generated noise are available, the efficient suppression of above-surface diffractions (ASDs) continues to be challenging. We have developed a scheme for semiautomatically detecting and suppressing ASDs. Initially, an accurate representation of ASDs is obtained by (1) Stolt [Formula: see text] migrating the GPR data using the air velocity to focus ASDs, (2) multichannel filtering to minimize other signals, (3) setting an amplitude threshold that targets the high-amplitude ASDs and effectively eliminates other signals, and (4) Stolt [Formula: see text] demigrating the ASDs using the air velocity, and remigrating them using the ground velocity. By excluding the obliquity correction in the Stolt algorithms and avoiding intermediate amplitude scaling, we preserve the ASDs’ amplitude and phase information. The final stepinvolves subtracting this image of ASDs from a standard migrated version of the original data. This scheme, which includes some important extensions to a previously proposed method, makes it possible to semiautomatically process large volumes of GPR data characterized by numerous highly clustered and overlapping ASDs. The user has control over the tradeoff between ASD suppression and undesired removal of useful signal. It achieves nearly complete removal of ASDs in synthetic data and significant suppression in field data. Once ASDs have been suppressed, their influence can be reduced further by applying relatively gentle multichannel filters. It is not possible to remove line diffractions that resemble subhorizontal reflections or retrieve subsurface signals from data saturated by ASDs, such that some blank regions may be left after applying the suppression scheme. Nevertheless, subsequent processing and interpretation of the GPR data benefit significantly from the suppression of ASDs, which otherwise would clutter the final images.

scholarly journals HIGH POWER BROADBAND PULSED MICROWAVE SOLID-STATE POWER AMPLIfIER WITH HIGH AMPLITUDE-PHASE STABILITY

2020 ◽  
Vol 258 (3) ◽  
pp. 53-59
Author(s):  
B. V. Emelyanov
Keyword(s):  
Mathematical Modeling ◽  
Solid State ◽  
Power Amplifier ◽  
Phase Stability ◽  
High Power ◽  
Theoretical Calculations ◽  
State Power ◽  
High Amplitude ◽  
Main Factors ◽  
The Stability

In this paper the principles of measuring the amplitude-phase stability are described. Fa ctors that negatively affect the amplitude-phase stability of a solid-state power amplifier are considered. The results of theoretical calculations and mathematical modeling of the dependence of this stability on various factors are presented, and on the basis of these results the main factors that negatively affect the amplitude-phase stability are identified. In the conclusion I present the results of practical measurements of the stability, and suggest methods to improve the amplitude-phase stability of high-power solid-state power amplifiers.

Theoretical study of the effect of thermal stress on transversal damage of hybrid biocomposite materials Flax-Hemp / Polyethylene

2021 ◽  
Vol 14 ◽  
Author(s):  
Allel Mokaddem ◽  
Bendouma Doumi ◽  
Mohammed Belkheir ◽  
Ahmed Boutaous ◽  
Elhouari Temimi
Keyword(s):  
Thermal Stress ◽  
Probabilistic Models ◽  
Theoretical Calculations ◽  
Environmental Benefit ◽  
Polyethylene Matrix ◽  
Acoustic Technique ◽  
Nonlinear Acoustic ◽  
Genetic Simulation ◽  
Good Agreement ◽  
Hybrid Biocomposite

Background: The objective of sustainable development in the field of materials necessitates and demands the substitution of the basic constituents of a composite material (carbon, glass, etc.) by natural reinforcements, which have a very important role in the protection of the environment and to subsequently have new materials with good properties compared to so-called traditional materials. Objective: In this context, we have investigated, using genetic modeling based on probabilistic models, the effect of thermal stress on transversal damage of a bio-composite hybrid Flax-Hemp/PE material. Method: Our model genetic is based on probabilistic models of Weibull and the different values of the thermal stress was calculated by the Lebrun equation. We used the nonlinear parameter β in the Hoock law of the nonlinear acoustic technique to trace the curves of the damage under the mechanical and thermal stress to validate our theoretical calculations. Results: The results obtained with a genetic simulation are in good agreement with the results found by Clément GOURIER and Raphaël KUENY, who have shown that flax and hemp fibers (bark/Liberian fibers) are good reinforcements of the Polyethylene matrix, we found also found that our hybrid biocomposite material Flax-Hemp/PE is resistant in particular, a part of this material is of plant origin and gives us environmental benefit. Conclusion: It should be noted that the results obtained by the genetic simulation are in good agreement with the results obtained by the nonlinear acoustic technique mentioned by the green curve in all the figures. In perspective, it would be interesting to see, later, the effect of humidity on the damage of the matrix fiber interface of a hybrid biocomposite.

THREE TIME-DOMAIN COMPUTATIONAL MODELS FOR QUASI-STANDING NONLINEAR ACOUSTIC WAVES, INCLUDING HEAT PRODUCTION

2006 ◽  
Vol 14 (02) ◽  
pp. 143-156 ◽  
Author(s):  
CHRISTIAN VANHILLE ◽  
CLEOFÉ CAMPOS-POZUELO
Keyword(s):  
Time Domain ◽  
Acoustic Waves ◽  
Computational Models ◽  
High Amplitude ◽  
Ultrasonic Waves ◽  
Physical Models ◽  
Industrial Processing ◽  
Strongly Nonlinear ◽  
Nonlinear Acoustic ◽  
The Time Domain

Applications of high-amplitude acoustic or ultrasonic waves in industrial processing require a good knowledge of the nonlinear pressure field, as well as the heat produced by the wave. In this article a new time-domain algorithm solving a second-order nonlinear wave equation written in Lagrangian coordinates and valid for any fluid is presented. The new model is compared with two others which were previously developed, corresponding to the two other possible physical approaches. This paper discusses the limits of application of every approach and the suitability of every one to model nonlinear acoustic waves in resonators. Conclusions about the applicability of the physical models are given. The time-domain character of the models allows the development of a new algorithm to calculate the temperature evolution inside a resonator due to acoustic losses. This algorithm is presented here and applied to strongly nonlinear waves for which the nonlinear attenuation is dominant. Several kinds of time functions for excitation can be considered in the models. The strongly nonlinear resonator response to a short pulsed signal is analyzed to show the efficiency of the time-domain numerical model.

The full acoustic wave train in a laboratory model of a borehole

Geophysics ◽  
1982 ◽  
Vol 47 (11) ◽  
pp. 1512-1520 ◽  
Author(s):  
S. T. Chen
Keyword(s):  
Acoustic Wave ◽  
Wave Velocity ◽  
Theoretical Calculations ◽  
Wave Train ◽  
High Amplitude ◽  
P Wave ◽  
Laboratory Model ◽  
Stoneley Wave ◽  
S Wave ◽  
Full Wave

We studied the characteristics of acoustic wave propagation in a fluid-filled borehole using as a laboratory model a concrete cylinder 2 ft high and 2 ft in diameter with a 1/4-inch diameter borehole along its axis. The model represents sonic logging in the field reduced by a factor of 40. We recorded the full wave train consisting of a refracted compressional P wave, a refracted shear S wave, and guided waves including a number of normal modes and a Stoneley wave. Exploiting the dispersive properties of a modal wave and the source-receiver frequency characteristics, we were able to isolate the S–wave, which contains much valuable information about the formation rock, but which has not been widely used since it is difficult to extract from the full wave train. The observed Stoneley wave had a very high amplitude at low frequency and showed little dispersion. Stoneley-wave velocity is closely related to S–wave velocity and formation density, and can be measured very accurately because the Stoneley wave generally has high amplitude and low attenuation. It can therefore be used indirectly to obtain the S–wave velocity, even when the S–wave cannot be measured directly. In general, the observed characteristics of each component wave agreed with our theoretical calculations but their relative amplitudes did not. We believe these discrepancies were caused, in part, by the fact that rock attenuation and the latitudinal angular dependence of the source radiation were not taken into account in the theoretical calculations.

scholarly journals Use of shock-wave exposures for accelerating thermal ablation of targeted tissue volumes

2019 ◽  
Author(s):  
Oleg Sapozhnikov ◽  
Wayne Kreider ◽  
Tatiana Khokhlova ◽  
Ari Partanen ◽  
Maria Karzova ◽  
...  
Keyword(s):  
Shock Wave ◽  
Thermal Ablation ◽  
Near Field ◽  
High Amplitude ◽  
Acoustic Propagation ◽  
Tissue Heating ◽  
Duty Cycles ◽  
Propagation Effects ◽  
Target Sites ◽  
Nonlinear Acoustic

In HIFU applications, nonlinear acoustic propagation effects can result in the formation of high-amplitude shocks at the focus, with amplitudes exceeding 100 MPa, leading to a significant increase in tissue heating at target sites. This effect has been used in a new pulsed-HIFU technology termed boiling histotripsy to mechanically liquefy tissue. In boiling histotripsy, such shock-wave millisecond-long pulses are delivered to the target sites at low duty cycles. Similar exposures, delivered at higher repetition rates may benefit thermal HIFU by shortening sonication and treatment times, reducing heating of near field and surrounding tissues, mitigating diffusion and perfusion effects, and providing sharper lesion margins. The goal of this project was to develop shock-enhanced thermal HIFU treatments and test their performance through a combination of simulations and experiments using a clinical Sonalleve V2 MR-HIFU system (Profound Medical Inc., Canada).

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