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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
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2013
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vol. 123
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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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Localization of Acoustic Signals Used in Sound Emitters at Pedestrian Crosswalks

100%
Niewiarowicz M., Furmann A.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1A
A-9-A-12
EN
This study aimed at determining an optimal acoustic signal, which could be used in sound emitters at blind and visually impaired enabled pedestrian crosswalks. Two signals were identified from among groups of tested signals on the basis of psychoacoustic tests. These two signals met the following standard requirements: TR signal - a signal with a triangular temporal envelope and a sinusoidal carrier and RC signal - a signal with a rectangular temporal envelope and a rectangular carrier, both with a basic frequency of 880 Hz, repeated periodically with a frequency of 5 Hz. The ability to localize was tested by a modified method of angle of directional hearing acuity in which the two alternative forced choice adaptation procedure was used. The test signals were emitted against the background of traffic noise and the ratio of the useful signal (65 dB SPL) to noise (75 dB SPL) was (-10 dB). The tests were conducted on 8 subjects with normal hearing (5 women and 3 men), aged 22-37 years. Following statistical analysis it was found that: individual subjects' responses differed considerably with respect to angle of direction hearing acuity values, localization is most difficult at the angles of 90° and 270°, worse localization for trams noise were stated, RC signals are better localized than TR signals.
3
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A New Method of Teaching Spatial Orientation to the Blind

37%
Hojan E., Jakubowski M., Talukder A., Wereda H., Furmann A., Ewertowski R., Skrodzka E., Perz P., Pękala P., Bogusz E., Lubawy H., Tomaszewski F., Czechyra B., Orczyk M., Szymański G., Niewiarowicz M., Hojan-Jezierska D., Jezierska A.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 1A
A-5-A-8
EN
Elaboration of a new method of teaching spatial orientation to blind and visually handicapped persons base on urban environment sounds was shown. Task 1 is a questionnaire inquiry on the problems of the blind moving in a big city. In Task 2 a preliminary selection and classification of the acoustic signals and vibrations that can be useful for spatial orientation was made. In Task 3 an analysis of acoustic signals for sound signalisation at pedestrian crossings was made. Some solutions for acoustic signalization were proposed. In Task 4 sounds and vibrations necessary for a library of acoustic events and situations characteristic of a city were recorded. In Task 5 the library was created and arranged to be ready to be used by teachers in the spatial orientation training. The most important outcome of the study was to develop a method of spatial orientation teaching with employment of sounds and verification of the method (Task 6). After verification it is concluded that the method is useful for spatial education of the blind at different levels of their education.
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