Electroacoustic Transducer Research Articles

Numerical simulation and experiments on mono-polar negative corona discharge applied in nanocomposites

The corona discharge techniques, which are employed to orient dipoles and built up charges inside functional polymers, can develop important commercial applications of electroactive polymers (EAPs) and electrets for energy storage devices, air filters, electroacoustic and electromechanical transducers. We propose hereby an elective hybrid approach to the point-plane corona modeling in order to obtain more accurate electron flow in unipolar corona discharge system. A coupled system of partial differential equations (PDEs) w.r.t. Navier-stokes equations and hydrodynamic drift diffusion equations described the nature of photo-ionization, where the secondary avalanche in the discharge process was demonstrated. The simulation was verified by comparison with Surface Potential (SP) measurement of the nano-composites after corona polarization. Consequently, the spacial electric potential distribution and initial surface potential could be obtained by the means of finite elements method (FEM), which provided a good numerical approach for the experimental data of electrostatic surface potential. In addition, the influence of nano particle on the charge retain ability of the insulating polymers was also investigated, which could be a guideline for designing an effective poling method on the functional polymers applied in electrical energy storage devices sensors, actuators and transducer etc.

Generation of acoustic helical wavefronts using metasurfaces

It has been shown that acoustic waves with helical wavefronts can carry angular momentum, which can be transmitted towards a propagating medium. Such a wave field can be achieved by using a planar array of electroacoustic transducers, forming a given spatial distribution of phased sound sources which produce the desired helical wavefronts. Here, we introduce a technique to generate acoustic vortices, based on the passive acoustic metasurface concept. The proposed metasurface is composed of space-coiled cylindrical unit cells transmitting sound pressure with a controllable phase shift, which are arranged in a discretized circular configuration, and thus passively transforming an incident plane wavefront into the desired helical wavefront. This method presents the advantage of overcoming the restrictions on using many acoustic sources, and it is implemented with a transmitting metasurface which can be easily three-dimensionally printed. The proposed straightforward design principle can be adopted for easy production of acoustic angular momentum with minimum complexity and using a single source.

PVDF Cylindrical Electroacoustic Emitting Transducer with Perforated Back-plate: Simplified Analytical Approach

PVDF Cylindrical Electroacoustic Emitting Transducer with Perforated Back-plate: Simplified Analytical Approach

Reviews of Ultrasonic Vibrodrives for Traumatology.

An investigation was made of the dynamics of ultrasonic vibrodrills with a common source of rotational and ultrasonic reciprocal motions. The source was constructed on the basis of an electroacoustic transducer of longitudinal vibrations. The dependences of power, rotation speed, and flutter rates were plotted for various pushers as a function of biological tissue drag torque. The results obtained allowed us to determine the optimal parameters of basic ultrasonic modes used in treating biological tissues. Apart from that, ultrasonic vibrodrill pilot models, which are new in principle, are presented. They were designed to be applied in traumatology. A distinguishing feature of these vibrodrills is that an electroacoustic transducer of longitudinal vibrations is a source of two motion types: rotational and ultrasonic reciprocal.

Modeling of Rocking Modes in Electroacoustic Transducers

Modeling of Rocking Modes in Electroacoustic Transducers

FBAR-on-diaphragm type electro-acoustic resonant micro-accelerometer: a theoretical study

We presented a theoretical study of the performance of a novel FBAR-on-diaphragm sensor-head structure for the FBAR-based electro-acoustic resonant micro-accelerometer. This structure overcomes disadvantages in the FBAR-beam structure for its limited cantilever beam thickness, and deficiencies in the embedded-FBAR structure for its complex micro-fabrication process. Its elastic diaphragm is made of silicon dioxide (SiO2)/silicon nitride (Si3N4) bilayer film, which is not only more susceptible to the IC compatible integration process for the Si-based microstructure and the FBAR, but also improves sensitivity and temperature stability of the BAW accelerometer. FBAR-on-diaphragm type BAW accelerometer integrates the acceleration sensing structure, i.e., the SiO2/Si3N4 bilayer diaphragm and the Si proof-mass, with the AlN FBAR electro-acoustic transducer. Preliminary performance analysis on FBAR-on-diaphragm type BAW accelerometer suggests that the FBAR-on-diaphragm structure is feasible. We obtained modal frequencies of the FBAR-on-diaphragm structure and stress distribution of the diaphragm under 0---100 g acceleration loads through the finite element modal analysis and static simulation, Applying the calculated maximum stress to the piezoelectric film in FBAR for qualitative analysis, and combining the dependency of elastic coefficient on stress in the Wurtzite AlN film calculated with the first-principle method, we roughly predicted the maximum elastic coefficient variation in the Wurtzite AlN film under different acceleration load. With the help of the RF simulation software ADS, we changed the longitudinal wave velocity corresponding to the elastic constants with variant acceleration loads. By comparing the resulted resonant frequencies of the sensor head without and with different acceleration loads, we qualitatively characterized its frequency shift and sensitivity. In our study, we gave further analysis of the simulation results. It reveals that the first-order modal frequency of the SiO2/Si3N4 circular diaphragm is quite far away from the higher ones, which means less cross modal coupling. It also reveals that under the acceleration load, its resonant frequency with a quite linear acceleration---frequency shift characteristic will up-shift with the sensitivity of several KHz/g.

Modelling and Parameters Study of Piezoceramic Parts of an Electroacoustic Transducers

the obtained results from the two models, the effects of the geometrical parameters on the frequency response of the ring and the surrounding domain in which the ring oscillates were studied. Based on the obtained results, the geometrical parameters have effects on both the frequency resonance of the ring, as well as the value of the electrical impedance. It is also noted that the surrounding domain only causes change on the intensity of the ring’s electrical impedance.

Functional Piezocrystal Characterisation under Varying Conditions.

Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0–60 MPa, temperature 20–200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I) binary, PMN-PT; (II) ternary, PIN-PMN-PT; and (III) doped ternary, Mn:PIN-PMN-PT. Utilising resonant mode analysis, variations in elastic, dielectric and piezoelectric constants and coupling coefficients have been analysed, and tests with thermal conditioning have been carried out to assess the stability of the piezocrystals under high power conditions.

ANSI/ASA S1.20-2012, “Procedures for Calibration of Underwater Electroacoustic Transducers,” Revision Details

The ANSI/ASA S1.20-2012 standard, “Procedures for Calibration of Underwater Electroacoustic Transducers,” was released in February 2012. It is a revision of American National Standard S1.20-1988 (R2003). An overview of the content of this standard inclusive of the typical primary and secondary open water procedures for determining the measurable characteristics of free-field receive voltage sensitivity and transmitting responses are examined along with highlights of materials that are new to the 2012 revision. In this later category, this presentation provides overview information contained in the S1.20-2012 related to correction factor application (with an emphasis on extension cable usage) and introductory material on measurement uncertainty analysis (along with the identification of common error sources). A cursory look at the informational annexes will also be addressed with an emphasis on the 2012 revision-specific ones related to medium correction factors, nonlinear effects including cavitation, and a standard-target method for calibrating active sonars.

Thermal fields of cylindrical piezoelectric electroacoustic transducers power constructions

Thermal fields of cylindrical piezoelectric electroacoustic transducers power constructions

Selection of modulation type in acousto-optic delay line with direct detection

This paper presents the physical and mathematical interpretation for the sequence of the response formation at the output of the acousto-optic delay line direct detection for various forms of connected to the terminals electro-acoustic transducer of high-frequency vibration. It has been shown that for the chosen design the intensity of light, which is incident on the photosensitive surface of the photodetector, varies only in the case of a change of acoustic power in the photoelastic medium. This eliminates the possibility of using the angular modulation for the transfer of video signal spectrum in the range of operating frequencies of the acousto-optic modulator in acousto-optic delay line with direct detection. In order to provide such a possibility it is recommended to install on the path of the deflected light a reference indicator, which converts the changes in the angle of diffraction into corresponding changes in the intensity of light, which is incident on the photosensitive surface of the photodetector. The proposed design is investigated for square and circular apertures of the light beam. It has been determined that best results are achieved in the case of the light beam with a square aperture and with a uniform distribution of power flow therein. We present the main results of experimental studies that confirm the effectiveness of the proposed design.

History of underwater electroacoustic transducer standards, calibration methods, facilities, and some early contributors

The practice of realizing underwater acoustic standards and methods for the systematic calibration of the wide variety of electroacoustic transducers is rich in tradition and has given rise to some unique facilities. In about 1940, the US Navy Office of Scientific Research and Development established a center for Underwater Acoustic Metrology under the expertise of Columbia University in collaboration with Bell Laboratories, which subsequently resulted in the establishment of the Underwater Sound Research Laboratory (USRL) in Orlando Florida with unique acoustic lake testing facilities. That facility later became a detachment of the Naval Research Laboratory (USRD) and was the home for a concerted effort in transducer development and calibration for many years. The National Bureau of Standards and later the National Institute for Standards (NIST) deferred the activity of establishing and maintaining underwater acoustic standards and calibration methods to the USRD Navy facility. This paper summarizes some of the transducers standards, methods and facilities and many of the important contributions of early pioneers in this field including Ira Groves, Robert Bobber, Joseph Blue, and others. USRD continues today as a division at NUWC, Newport.

A Versatile Model of Nonlinear Electrodynamic Loudspeaker Co-Operating with the Amplifier Designed by Way of Advanced Software

Abstract Sound processing with loudspeaker driving depends critically on high quality electroacoustic transducers together with their relevant amplifiers. In this paper, the nonlinear effects of electrodynamic loudspeakers are investigated as regard the influence of the changes of their main descriptive parameters values. Indeed, while being operated nonlinear effects observed with loudspeakers are due to changes of such constitutive parameters. Regarding either current or voltage-drive, an original model based on Simulink R is presented, taking account of all the electrical and mechanical properties closely associated with nonlinear behaviours. Moreover, as such a Simulink R model may be combined with the PSpice R advanced software, the behaviour of both loudspeaker and amplifier can be exhaustively investigated and optimized. To this end, the amplifier is simulated thanks to the Orcad-Capture-PSpiceR software prior to match with the loudspeaker model with the so-called SLPS co-simulator. Then, values of the current flowing through the loudspeaker can be determined and plotted considering voltage controlling. Obviously in this case current-drive has not to be assessed. This way to proceed allows us to highlight any critical information especially due to the voice coil displacement, yielded velocity, and acceleration of the diaphragm. Indeed our approach testifies to the imperative necessity of mechanical measurements together with electrical ones. Then, considering a given amplifier-loudspeaker association with specific parameters changes of the latter, the entailed nonlinear distortion allows us to qualify and criticize the whole design. Such an original approach should be most valuable so as to match the best fitted amplifier with a given electrodynamic loudspeaker. Then non linear effects due to voltage and current-drive are compared highlighting the advantages of an apt currentcontroled policy.

Stable sound wave generation in weakly ionized air medium

Results of experimental and theoretical research of the laboratory prototype of "diaphragmless" non-thermal electroacoustic transducer of original design, working as a broadband acoustic monopole are discussed.Radiation patterns of acoustic emission, current-voltage characteristic of corona discharge at the given electrode geometry were investigated, based on which a theoretical scheme for calculating the acoustic emission power depending on the magnitude of the potential difference between the electrodes was built. The calculation of the basic characteristics of the loudspeaker was performed within the quasi-stationary approximation using a standard three-component hydrodynamic model of weakly ionized gas, supplemented by the equations of chemical kinetics.It is shown that the sound generation process is a scalar effect, arising due to the gas ionization degree modulation.The theoretical model, developed in the paper is the basis for a detailed simulation of sound generation processes, and possible improvement of the proposed design of so-called "ionic loudspeaker".

The phonodeik: Measuring sound pressure before electroacoustic transducers

The modern ability to visualize sound pressure waveforms using electroacoustic transducers began with the development of the vacuum tube amplifier, and has steadily improved as better electrical amplification devices have become available. Before electoral amplification was available; however, a significant body of acoustic pressure measurements had been made using the phonodeik, a device developed by Dayton C. Miller in the first decade of the twentieth century. The phonodeik employs acoustomechanical transduction to rotate a small mirror that reflects an optical beam to visualize the pressure waveform. This presentation will review the device and some of the discoveries made with it.

The Graduate Program in Acoustics at The Pennsylvania State University

In 2015, the Graduate Program in Acoustics at Penn State will be celebrating 50 years as the only program in the United States offering the Ph.D. in Acoustics as well as M.S. and M.Eng. degrees in Acoustics. An interdisciplinary program with faculty from a variety of academic disciplines, the Acoustics Program is administratively aligned with the College of Engineering and closely affiliated with the Applied Research Laboratory. The research areas include: ocean acoustics, structural acoustics, signal processing, aeroacoustics, thermoacoustics, architectural acoustics, transducers, computational acoustics, nonlinear acoustics, marine bioacoustics, noise and vibration control, and psychoacoustics. The course offerings include fundamentals of acoustics and vibration, electroacoustic transducers, signal processing, acoustics in fluid media, sound-structure interaction, digital signal processing, experimental techniques, acoustic measurements and data analysis, ocean acoustics, architectural acoustics, noise control engineering, nonlinear acoustics, ultrasonic NDE, outdoor sound propagation, computational acoustics, flow induced noise, spatial sound and 3D audio, marine bioacoustics, and the acoustics of musical instruments. Penn State Acoustics graduates serve widely throughout military and government labs, academic institutions, consulting firms, and industry. This poster will summarize faculty, research areas, facilities, student demographics, successful graduates, and recent enrollment and employment trends.

Pursuing the M.Eng. in acoustics through distance education from Penn State

Since 1987, the Graduate Program in Acoustics at Penn State has been providing remote access to graduate level education leading to the M.Eng. degree in Acoustics. Course lecture content is currently broadcast as a live-stream via Adobe Connect to distance students scattered throughout North America and around the world, while archived recordings allow distance students to access lecture material at their convenience. Distance Education students earn the M.Eng. in Acoustics degree by completing 30 credits of coursework (six required core courses and four electives) and writing a capstone paper. Courses offered for distance education students include: fundamentals of acoustics and vibration, electroacoustic transducers, signal processing, acoustics in fluid media, sound and structure interaction, digital signal processing, aerodynamic noise, acoustic measurements and data analysis, ocean acoustics, architectural acoustics, noise control engineering, nonlinear acoustics, outdoor sound propagation, computational acoustics, flow induced noise, spatial sound and 3D audio, marine bioacoustics, and acoustics of musical instruments. This poster will summarize the distance education experience leading to the M.Eng. degree in Acoustics from Penn State showcasing student demographics, capstone paper topics, enrollment statistics and trends, and the success of our graduates.

Developments in standards and calibration methods for hydrophones and electroacoustic transducers for underwater acoustics

If they are to be meaningful, underwater acoustic measurements must be related to common standards of measurement. In this paper, a description is given of the existing standards for the calibration of hydrophones and electroacoustic transducers for underwater acoustics. The description covers how primary standards are currently realized and disseminated, and how they are validated by international comparisons. A report is also given of the status of recent developments in specification standards, for example within the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). The discussion focuses on the revision of standards for transducer calibration, and the inclusion of extended guidance on uncertainty assessment, and on the criteria for determining the locations of the acoustic near-field and far-field. A description is then provided of recent developments using non-traditional techniques such as optical sensing, which may lead to the next generation of standards. A report is also given of the status of recent developments in and of a number of current initiatives to promote best measurement practice.

Method of calculation of temperatures of warming-up of constructions of cylindrical electro-acoustic transducer of the compensated type, pressurized by the metal-polymer layers

Method of calculation of temperatures of warming-up of constructions of cylindrical electro-acoustic transducer of the compensated type, pressurized by the metal-polymer layers

Nearfield of an electroacoustic transducer, with implications for performance measurement

The spatial structure of the nearfield of an electroacoustic transducer is known to be complicated. This is illustrated by numerical modeling of the nearfield of an ideal planar circular piston in a rigid, infinite baffle. There are implications for performance measurements of electroacoustic transducers including hydrophones in tanks.