Electro-acoustic Converter Research Articles

Construction, testing and performance analysis of a multi-stage traveling-wave thermo-acoustic generator

ABSTRACT This research describes the construction and testing of a multi-stage thermo-acoustic generator that demonstrates the potential of conversion of waste heat into useful electricity. The total length of the traveling-wave loop was 3 560 mm. The thermo-acoustic engine stages were positioned 640 mm apart. An experimental investigation into the effects of the heat source on the potential of the device for electricity generation has been conducted. The magnitude of the sound pressure level generated by the engines, the onset time and the magnitude of electricity generated by the electroacoustic converter have been considered as performance indicators for the device developed. This paper provides details of the experimental investigation by measures of these indicators. A single-stage thermo-acoustic system, tested separately, generated an average output voltage of approximatively 834 mV. A second stage was added into the traveling-wave loop. The two-stage system generated an output voltage of approximately 1.55 V. A third stage was added into the loop. The three-stage system generated an output voltage of 2.362 V. The subsequently added four-stage thermo-acoustic system generated an average maximum output voltage of 4.218 V.

Development of piezoceramic electroacoustic transducers for acoustic devices with a sound pressure of 125 dB or more

The increased sound pressure level of piezoceramic electroacoustic transducers is important for acoustic devices designed to create high-intensity sound, 125 decibels or more. This is especially true of acoustic devices that use a group of transducers. An electroacoustic transducer that develops a higher sound pressure can greatly reduce the number of radiating elements in an acoustic device. In the performed work electroacoustic transducers are created that capable to develop sound pressure level up to 125 dB. The article presents the results of the development of electroacoustic transducers for three frequency versions. The scheme of the generator of the exciting voltage for electroacoustic converters with the raised sound pressure is offered and investigated. The result is particularly relevant when used in multi-element sound-emitting devices, as repeatedly reduces the required number of converters to achieve the same result.

Control of Surface Density of Textile Materials Using Automated Scanning System

The paper demonstrates the importance of controlling the surface density of textiles, which include mainly fabrics, knitted fabrics and nonwoven fabrics, in order to improve the quality of their manufacture.
 It considers the most accurate methods of controlling surface density by determining the mass to area ratio of the textile sample. And it is also shown that, in addition to high accuracy, such met­hods have many fundamental disadvantages: the need to obtain a sample of textile material, low productivity, inability to automate the process of determining surface density, and so on.
 In addition, it deals with optical methods for controlling surface density based on the imaging of textile material and its subsequent analysis. However, the presence of factors such as entanglement complexity, the presence of pores, and some others does not fully reveal the potential of optical surface density methods.
 The paper also shows that at different points in the surface of the textile material, its surface density may differ significantly from its average value. Therefore, there is a need for an automated scanning system that allows radiating and receiving electroacoustic converters to be moved to exactly the point of the surface of the textile material whose surface density requires measurement.
 In order to solve the problem, it was proposed to use a toothed belt gear, and to drive it with the help of step motors controlled through drivers. In turn, to communicate drivers with the control computer, it was proposed to use a microcontroller with an integrated USB interface (for example, manufactured by Microchip Technology Inc.), and software for it to write in one of the high-
 level programming languages (for example, C #).
 This construction of the automated scanning system is due to the fact that the existing means of linear movement, in terms of the design of the scanning system, have a lot of redundancy: too much cost, too much accuracy, the need to use specialized software, and so on.
 The use of the proposed linear positioning means will allow the scanning system to have sufficiently high metrological characteristics at a relatively low cost.

Technology and Electrophysical Properties of the (K0.44Na0.52Li0.04) NbO3 Ceramics Doped by Cr3+, Zn2+, Sb3+ or Fe3+

[1] M. Venkata Ramana, S. Roopas Kiran, N. Ramamanohar Reddy, K.V. Siva Kumar, V.R.K. Murthy, B.S. Murty, Investigation and characterization of Pb(Zr0.52Ti0.48)O3 nanocrystalline ferroelectric ceramics: By conventional and microwave sintering methods, Materials Chemistry and Physics 126, 295-300 (2011). [2] R. Skulski, D. Bochenek, P. Wawrzala, G. Dercz, D. Brzezinska, Technology and properties of PBZTS ceramics, International Journal of Applied Ceramic Technology 10, 2, 330-338 (2013). [3] R. Zachariasz, D. Bochenek, Parameters of ceramics obtained on the base PZT used to build electroacoustic converters, Journal de Physique IV 137, 189-192 (2006). [4] R. Zachariasz, D. Bochenek, K. Dziadosz, J. Dudek, J. Ilczuk, Influence of the Nb and Ba dopands on the properties of the PZT type ceramics, Archives of Metallurgy and Materials 56, 4, 1217-1222 (2011). [5] G. Vats, R. Vaish, C.R. Bowen, Selection of Ferroelectric Ceramics for Transducers and Electrical Energy Storage Devices, International Journal of Applied Ceramic Technology 12, S1, E1-E7 (2015). [6] G. Vats, R. Vaish, Piezoelectric material selection for transducers under fuzzy environment, Journal of Advanced Ceramics 2, 2, 141-148 (2013). [7] G. Vats, R. Vaish, Selection of Lead-Free Piezoelectric Ceramics, International Journal of Applied Ceramic Technology 11, 5, 883-893 (2014). [8] G. Vats, R. Vaish, Selection of optimal sintering temperature of K0.5Na0.5NbO3 ceramics for electromechanical applications, Journal of Asian Ceramic Societies 2, 5-10 (2014). [9] G.Z. Zang, X.J. Yi, J. Du, Z.J. Xu, R.Q. Chu, P. Fu, W. Li, Microstructure and electric properties of (Na0.015-xKx)NbO3 lead--free piezoceramics, Journal of Materials Science Materials in Electronics 22, 1282-1285 (2011). [10] R.-A. Eichel, E. Erunal, P. Jakes, S. Korbel, C. Elsasser, H. Kungl, J. Acker, M.J. Hoffmann, Interactions of defect complexes and domain walls in CuO-doped ferroelectric (K,Na)NbO3, Applied Physics Letters 102, 242908 (2013). [11] J. Hrescak, A. Bencan, T. Rojac, B. Malic, The influence of different niobium pentoxide precursors on the solid-state synthesis of potassium sodium niobate, Journal of the European Ceramic Society 33, 3065-3075 (2013). [12] M.R. Bafandeha, R. Gharahkhani, J.-S. Lee, Comparison of sintering behavior and piezoelectric properties of (K,Na)NbO3--based ceramics sintered in conventional and microwave furnace, Materials Chemistry and Physics 143, 1289-1295 (2014). [13] P. Bharathi, K.B.R. Varma, Effect of the Addition of B2O3 on the Density, Microstructure, Dielectric, Piezoelectric and Ferroelectric Properties of K0.5Na0.5NbO3 Ceramics, Journal of Electronic Materials 43, 2, 493-505 (2014). [14] L.A. Ramajo, J. Taub, M.S. Castro, Effect of ZnO Addition on the Structure, Microstructure and Dielectric and Piezoelectric Properties of K0.5Na0.5NbO3 Ceramics, Materials Research 17, 3, 728-733 (2014). [15] P. Bomlai, S. Sukprasert, S. Muensit, S.J. Milne, Phase development, densification and dielectric properties of (0.95-x)Na0.5K0.5NbO3-0.05LiTaO3-xLiSbO3 lead free piezoelectric ceramics, Songklanakarin Journal of Science Education and Technology 30, 6, 791-797 (2008). [16] V.J. Tennery, K.W. Hang, Thermal and X-ray diffraction studies of NaNbO3-NbO3 system, Journal of Applied Physics 39, 4749-4753 (1968). [17] J. Rodel, W. Jo, K.T.P. Seifert, E.M. Anton, T. Graznow, D. Damjanovic, Perspective on the Development of Lead-free Piezoceramics, Journal of the American Ceramic Society 92, 6 1153-1177 (2009). [18] H.M. Rietveld, A profile refinement method for nuclear and magnetic structures, Journal of Applied Crystallography 2, 65-71 (1969). [19] M. Morawiec, A. Grajcar, Some aspects of the determination of retained austenite using the Rietveld refinement, Journal of Achievements in Materials and Manufacturing Engineering 80, 1, 11-17 (2017). [20] R. Rani, S. Sharma, Influence of sintering temperature on densification, structure and microstructure of Li and Sb Co-Modified (K,Na)NbO3-based ceramics, Materials Sciences and Applications 2, 1416-1420 (2011). [21] S. Qian, K. Zhu, X. Pang, J. Wang, J. Liu, J. Qiu, Influence of sintering temperature on electrical properties of (K0.4425Na0.52Li0.0375)(Nb0.8825Sb0.07Ta0.0475)O3 ceramics without phase transition induced by sintering temperature, Journal of Advanced Ceramics 2, 4, 353-359 (2013). [22] R.E. Jaeger, L. Egerton, Hot-pressing of potassium sodium niobates, Journal of the American Ceramic Society 45, 5, 209-213 (1962).

Recovery of the form of acoustic signals in experiments with rock samples

The formation of signals in the receiving channel of the recording system is assumed to be described by the linear procedure of convolution (Duhamel’s integral) in the first approximation. In this case, distortions caused by irregularity in the amplitude-frequency characteristic of electroacoustic converters (receivers) can be reduced and a real form of input signals can be recovered. To do this, it is required to know the impulse characteristic of the receiver and the amplifying part of the input channel of the system and to perform secondary data processing. A principal possibility of recovering a form of the input signals in such a way is shown.

Calculation of electrical strength of structures electroacoustic transducers sealed with polymer materials

Electric strength of electro-acoustic converters dependence on service conditions and hermetic encapsulation modes is considered. Settlement models for diffusion processes estimation in electro-acoustic converters with various variants of hermetic encapsulation and protection against voltage failure are developed. The models dependences of diffusion processes speed on properties of used materials are established

Method and apparatus for controlling the reproduction in audio signals in electroacoustic converters

The aim of the invention is to control the bass reproduction of audio signals in electroacoustic transducers based on the psychoacoustic principle denoted by the term “virtual pitch” or “residual hearing (hearing of missing fundamental)”, in such a way that the perception of the virtual bass reproduction of the audio signals is improved in relation to prior art. To this end, the reproduction of the low pitched frequencies or basses released in the electroacoustic transducer is controlled by the amplification of the harmonic waves already contained in the audio signals, in the form of a simulation, in such a way that the listener experiences or perceives an improved bass reproduction. The control or simulation can thus be carried out in both a digital manner, by means of a program module in a digital signal processor of an electronic appliance for outputting and/or reproducing audio signals using the electroacoustic transducer, and in an analog manner, by means of a hardware circuit between a digital analog transducer and a final amplifier of the electronic appliance for outputting and/or reproducing audio signals using the electroacoustic transducer.

Electro-acoustic converter with demountable diaphragm and voice coil assembly

A compound loudspeaker drive unit comprising a first drive unit and a second drive unit arranged co-axial with respect to the center axis of the loudspeaker, and each drive unit comprises permanent magnet means and pole piece means together forming a magnetic circuit with a pole gap for exciting a voice coil assembly, each pole gap providing magnetic field directed radially with respect to a center axis of the loudspeaker. At least one of the permanent magnet means has a radially extending magnetization direction with respect to said center axis of the loudspeaker and the acoustic centers of said drive units substantially coincide.

Drive unit for electro-acoustic converter with radially magnetized permanent magnetic bars

An electro-acoustic drive unit includes at least one permanent magnet assembly and at least an inner pole piece and an outer pole piece forming a pair of pole pieces, the permanent magnet assembly together with the pair of pole pieces forming a magnetic circuit with a pole gap for exciting a voice coil assembly. The pole gap is arranged to provide a magnetic field directed radially with respect to a center axis of the loudspeaker, and the permanent magnet assembly includes at least two permanent magnetic bars, with radially extending magnetization direction with respect to the center axis of the loudspeaker.

Double wire cord and portable audio device using the same

A double wire cord is used in an electro-acoustic converter, such as earphones and headphones, and has a long first cord and a long second cord. For example, the first cord is substantially circular in cross section and has a large diameter, the second cord is also substantially circular in cross section and has a small diameter, and the second cord can be removably housed in the first cord. The second cord is fitted into the fitting groove of the first code and thus housed in the first cord by pressing the side surface of the second cord against the fitting groove of the first cord, so that one wire cord can be easily provided. Therefore, it is convenient at the time of use and storage.

Process to adapt the signal amplification in a hearing device as well as a hearing device

A input signal for a hearing device signal processing unit is generated with the aid of an electro-acoustic converter. An output signal is generated by applying signal amplification. The signal amplification is adapted by determining a reference level of the input signal using statistical calculation methods. A minimum input signal level is determined by subtracting a predefined difference value from the reference level of the input signal. An amplification function is applied to the input signal when the signal level is less than the minimum input signal level. This amplification function is different from an amplification function applied when the signal level is greater than the minimum input signal level.

Parameters of ceramics obtained on the base PZT used to build electroacoustic converters

Modifying the basic chemical compositions of converters, obtained on the base of two -component solid solutions of the PZT type, is possible by the use of suitable dopants. In the work the complex of electric parameters, such as: k p , e, tgδ, d 31 , S H E , E C , P, was determined for five different compositions of ceramics of the PZT type, used to product electroacoustic converters. The samples to research were condensed by conventional ceramic sintering method, replacing partly the ions Pb 2+ with ions Ba 2+ or Sr 2+ . To basic chemical compositions of ceramic samples, hard: Mn 2+ and Cr 2+ or soft: Nb 5+ dopants were introduced. too.

Electro-acoustic converter

An electro-acoustic converter, comprising a barrel shaped diaphragm ( 2 ) formed about a longitudinal axis ( 3 ) and comprising first and second annular opposed ends ( 4, 5 ), and a first electrically driven vibration generator ( 6 - 11 ) for inducing a vibrational movement in the first annular end in the direction of the longitudinal axis.

Audio-visual arrangement and system in which such an arrangement is used

An audio-visual arrangement (1), more particularly, a multi-media terminal, comprises a picture screen (6) on which pictures can be displayed. The arrangement (1) further comprises a plurality of electro-acoustic converters (2, 3, 4, 5) for reproducing sound that corresponds to audio information generated by the audio signal source (21). The converters (2, 3, 4, 5) are positioned at regular mutual distances along one side of the picture screen (6). The radio of the strength of the control signals applied to the converters (2, 3, 4, 5) has values for which a sound wave concentration is obtained in a listening/viewing area situated dead opposite to the picture screen. With the audio-visual arrangement (1) the nuisance of noise experienced in a living space and/or working space by persons other than the user of the arrangement remains limited. A further reduction of the nuisance can be obtained by a system in which the audio-visual arrangement (1) is combined with means for active noise abatement.

Electroacoustic energy converter for transformation between thermal and electrical energy

Electroacoustic converter for transformation between thermal and electrical energy, comprising working chamber filled with working medium, piezoelectric transducer, acoustic filter and source of gaseous substance to be supplied into working chamber under pressure. Combustion of gaseous substance causes its pulsation accompanied by emitting acoustic waves, which being transmitted via working medium to said transducer are converted into electrical signals. The signals can be released from the electrical terminals of transducer. The same device can function in opposite direction in the sense that it converts the supplied to transducer electrical energy into acoustical waves which being emitted by the transducer are transferred through the working medium to the gaseous stream. This process is accompanied by adiabatic heating and cooling of the stream and thus transferring of electrical energy into heat energy takes place while converter operates as a heat machine.

An arm phantom: a digital simulation system for testing sphygmomanometers

An arm phantom for testing non-invasive blood pressure measuring instruments under reproducible and real conditions has been developed. Signal records, recorded on patients and validated by a reference method, are played into the instruments to be tested using a combination of an electro-pneumatic and an electro-acoustic converter. For each of 90 patients a database contains records of at least three different kinds of signal: cuff pressure oscillations, Korotkoff sounds (except in neonates) and cuff pressure. As the inflation and deflation rate varies between different sphygmomanometers the control and synchronization of the signal output are ensured as a function of the instantaneous cuff pressure, measured continuously by the system. A segmented output procedure synchronizes the data flow during the test procedure. The records of blood pressure signals are separated in different signal groups, containing only one pressure oscillation and Korotkoff sound respectively, whereas the instantaneous cuff pressure determines the signal group to be selected. Suitable interfaces to the sphygmomanometers under test consist of two specifically developed signal converters, an electro-pneumatic converter and an electro-acoustic converter. The system generates both cuff pressure oscillations and Korotkoff sounds from real data earlier recorded on human subjects. It allows any inflation and deflation rate of the cuff pressure to be applied, considers the variability of the pulse rate occurring in the same data record and finally it allows the superposition of artefacts. The arm phantom can replace clinical trials. The possibility of testing the limits of the performance of sphygmomanometers has been considerably extended.

Telephone handset with electroacoustic converters electrically connected by a cord

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Electro-acoustic converter with compensated frequency response characteristic

A device for converting an electric signal into an acoustic signal, which comprises an electro-acoustic transducer unit (2) having a quality factor (Q) less than unity. The device further comprises an amplifier circuit (3) for driving the transducer unit. The amplifier circuit has a frequency-dependent gain characteristic (6) which increases towards the lower frequencies, starting from f 2 , in a frequency range between a first and a second frequency (f 1 and f 2 ), f 1 being the resonant frequency of the transducer unit (2) and f 2 being greater than f 1 . The efficiency can be increased if amplifier the circuit includes a special amplifier such as a switched amplifier, for example, a class-D amplifier, or an amplifier with a power supply that provides a DC voltage that depends on the drive level of the amplifier.

Hearing aid responsive to signals inside and outside of the audio frequency range

A hearing aid having a microphone (10), a microcomputer (12) for digital signal processing of digitized microphone signals and an electroacoustic converter (14) for acoustic reproduction of the processed digitized signals, is equipped with at least one further sensor (16, 18) responsive to signals outside the acoustical range of audibility. These further sensor signals are processed according to a different program stored in a second memory (19) and supplied as additional data via an output (B2) of the microcomputer (12) preferably to the electro-acoustical converter (14). As a result, data such as the signals of a traffic light transmitter, signals from a paging system, or signals announcing a telephone call, door bell or the like, can be superimposed on the normal auditory functions. By appropriately coordinate signal trains, for example generated in accordance with the program stored in the second memory, a hearing-impaired person can easily distinguish among these additional functions.

Oscillatory circuit for electro-acoustic converter, with starting means operating at the ultrasonic mechanised resonant frequency of the converter: Shoh, A., and Wilkens, H.J. USA Patent 3, 469, 210 (23 September 1969) (Filed 16 October 1967) (2313)

Oscillatory circuit for electro-acoustic converter, with starting means operating at the ultrasonic mechanised resonant frequency of the converter: Shoh, A., and Wilkens, H.J. USA Patent 3, 469, 210 (23 September 1969) (Filed 16 October 1967) (2313)