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1
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Subjective Evaluation of Directional Properties of Loudspeaker Systems with the Analog and Digital Crossover Networks

100%
Niewiarowicz M., Galiński T.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 6
974-979
EN
The aim of this study was to determine the way in which loudspeaker systems with the analog and digital crossover networks were subjectively evaluated. The object of the study were two loudspeaker systems, differing in both the position of speakers on the front panel of enclosure and configuration of the crossover networks: 2.5-way and 3-way systems with the slope of frequency response of 12 dB/octave in the cut-off regions. The investigations were conducted for 5 angles from the front hemisphere in the horizontal plane. Test signals were fragments of music and speech. The recordings of these signals were conducted in an anechoic chamber using an artificial head and then presented to the listeners through headphones. Five normally-hearing listeners aged 18-50 years took part in the experiment. Listening tests were carried out in two stages. In the first stage listeners were listening to test signals grouped in triads and their task was to identify pairs of signals the most and the least similar to each other. In the second stage a parametric evaluation was performed. It consisted in assigning five numbers, corresponding to the intensity of the attribute of perception space (evaluated on a scale of 0-10) to each of test signals. The attributes of perception space included: sharpness, clearness, fullness, lack of distortions and loudness. Using the method of multidimensional scaling and correlation analysis it was possible to relate a particular dimension of the multidimensional space to the attributes of the perception space. It was found that the intrinsic attributes responsible for the subjective evaluation of loudspeaker systems with the analog and digital crossover network were sharpness, clearness and loudness.
2
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Investigation on Vibrations of a Cantilever Beam with Magnetorheological Fluid by Using the Acoustic Signal

80%
Snamina J., Sapiński B., Wszołek W., Romaszko M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1A
A-188-A-190
EN
The paper presents results of laboratory investigations of a vibrating three-layer cantilever beam with magnetorheological fluid. The goal of the study was to determine changes of the acoustic field around the vibrating beam caused by modifications of the magnetorheological fluid properties. The experimental studies have been carried out on a dedicated measuring stand. The construction of the measuring stand allows fixing one end of the beam in a holder attached to the moving part of the electrodynamic shaker. The magnetic field is produced by an external electromagnet. During the measurements the beam displacements and the acoustic pressure have been simultaneously registered. Frequency analysis of the registered signals has been carried out in 1/12 octave bands near the second natural frequency of the beam. The results reveal that the acoustic signal emitted by the vibrating beam decreases when the magnetic field is applied.
3
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Piezoceramic Transducers Selection Method for High Power Ultrasonic Devices

61%
Kluk P., Milewski A.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 3
719-722
EN
A universal method for selecting piezoceramic transducers used in high power ultrasonic devices such as ultrasonic welding and cutting systems has been presented. The key element of such systems is a high power ultrasonic sandwich transducer consisting of a stack of piezoceramic transducers mounted between two masses. Because of relatively large dispersion of piezoceramic transducer parameters between production lots, they must be selected in order to obtain a high quality and long-life sandwich transducer. Presented selection method consists of three stages. First, the parametric identification of the Butterworth-Van Dyke equivalent circuit model is performed based on piezoceramic transducer electrical impedance measurements. Next, the electrical impedance frequency samples are estimated using the identified Butterworth-Van Dyke model. Finally, the k-means clustering algorithm is used to select the best fitted piezoceramic transducer sets.
4
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Influence of Refractive Indices Dispersion on Parameters of Imaging AOTFs Operating with Non-Polarized Light

61%
Yukhnevich T., Voloshinov V., Pritulenko I.
Acta Physica Polonica A
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2015
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vol. 127
|
issue 1
78-80
EN
The paper presents results on investigation of paratellurite based imaging tunable acousto-optic filters operating with arbitrary polarized light. We analyzed influence of dispersion of refractive indices in the crystal on a simultaneous satisfaction of the Bragg matching condition for ordinary and extraordinary polarized optical beams. The analysis was carried out at different optical wavelengths over the wide tuning range of the filters 400-1150 nm. Theoretical and experimental analysis of the problem proves that in a paratellurite tunable acousto-optic filter, the Bragg matching angle common for the two optical polarizations is varying in the limits up to 0.3°. This variation of the incidence angle may be as wide as a quarter of the filter angular aperture thus proving that the examined phenomenon should be considered in design of the imaging tunable acousto-optic filters.
5
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New Multimode Sonotrodes Models Designed for Rotary Ultrasonic Welding Systems

61%
Kogut P., Milewski A., Kardyś W., Kluk P., Gawryś P.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
474-478
EN
The paper presents methods of designing sonotrodes, working in varied mechanical vibration modes in high power application regime such as rotary ultrasonic welding systems. The aim of the sonotrode design process is to optimize its shape to achieve the best energy efficiency for a given welding process. Sonotrode geometry influences the power transferred to the welded element because it determines the vibration amplitude distribution in the sonotrode. The most popular applications use sonotrodes designed for axial vibration. Conducted research have shown that the optimal displacement and strain distribution is achieved for sonotrodes working in various vibration modes such as axial, transverse, radial or their compositions. In the paper examples of multimode sonotrode models for various rotary ultrasonic welding technologies have been presented.
6
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Measurement System for Parameter Estimation and Diagnostic of Ultrasonic Transducers

51%
Kluk P., Milewski A., Kardyś W., Kogut P., Michalski P.
Acta Physica Polonica A
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2013
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vol. 124
|
issue 3
468-470
EN
The paper presents an architecture and design of measurement system and methods for parameter estimation and diagnostic of ultrasonic transducers used in ultrasonic welding and cutting systems manufactured by Tele and Radio Research Institute. The key element of the ultrasonic welding and cutting system is a high power ultrasonic transducer implemented as a sandwich transducer consisting of a stack of piezoelectric ceramic rings mounted between two masses. High quality welding and cutting demand predetermined frequency characteristic of transducer impedance. Also important are: high energy efficiency, high coupling coefficient, low dielectric loss, and the optimal radiation pattern. In order to manufacture high quality and long-life transducers the piezoelectric rings must be selected and the sandwich transducers diagnosed on the basis of their measured parameters. Presented measurement system takes advantage of the virtual instrument technique in the NI LabVIEW environment. It uses Agilent U2761A Function Generator, U2531A Data Acquisition Unit, and the linear amplifier to measure impedance frequency characteristic in the frequency range of 10 kHz to 100 kHz. Moreover, the system can measure the vibration amplitude in the range of 1 μm up to 100 μm, using an optical sensor, and the temperature of the transducer using a pyrometer sensor.
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