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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.
EN
The auditory impression of sound sources is strongly influenced by the room, which, e.g., determines the apparent source width. What is more, typical sources are not omnidirectional, which also makes their orientation a strong influence. This influence, however, has only been investigated a little, although it can even change the perceived location of the source. To provide more insight, we performed extensive listening experiments inside our anechoic laboratory that is equipped with a 24-channel loudspeaker playback to simulate both the directional source and the room. The directional source is described by two frequency-independent 3rd order directivity designs in 36 different orientations, and the room is simulated by the two-dimensional 1st and 2nd order image source method. Results of the experiment indicate that, in most cases, the auditory location can be determined by the loudest unmasked acoustic reflection path. This allows to explain the primary direction perceived with an astonishingly simple model including precedence effects.
EN
Performance of blind/visually impaired children and teenagers before and after the auditory training and the music training in some auditory tasks (pitch discrimination, pitch-timbre categorization, pitch memory, lateralization of a stationary sound of a drum, lateralization of one or two moving motor vehicles) is compared. In the auditory training, the subjects were actively involved, i.e. they had to answer questions related to presented sound material. The music training was based on passive listening to sounds presented according to the Tomatis method. The training (auditory or music) effectiveness was measured as a difference between results of a pre- and post-training verification test in which the subjects were asked to perform the auditory tasks mentioned at the beginning. The persons who took part in the study were divided into two age groups: 7-12 year olds and 13-19 year olds. According to the results, the auditory training was beneficial for blind or visually impaired teenagers, especially in respect of lateralization tasks. For small children the auditory training was not as effective as for adolescents. However, it has been shown that the music training was generally beneficial for them, although none of the verification tasks was privileged.
EN
Results of an auditory training for blind/visually impaired children and teenagers are presented. A measure of the training effectiveness is the difference between the results of a pre- and post-training verification test. Two age groups of visually handicapped young persons were tested: 7-12 years old and 14-19 years old. It was shown that the training may be beneficiary for blind or visually impaired children and teenagers, especially in tasks related to localization of moving sound sources. No differences in training results were found between age groups. The results of trained groups were compared to those obtained for not trained control groups of young blind individuals.
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Diver Observations by Means of Acoustic Methods

51%
EN
Searching for objects, especially small ones, moving under water near its the free surface, is always not an easy task. Designing tools for the detection of such targets is a real challenge when the possibility of a terrorist attack is a real threat. This paper presents some aspects of diver detection by means of acoustics methods, both active (side scan sonar) and passive ones (linear receiving antenna). This approach is quite effective because divers can use both breathing apparatus operating in the closed-loop (so-called rebreathers), and popular open-circuit breathing (exhalation of used air or a breathing gas mixture into the water).
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vol. 125
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issue 4A
A-31-A-37
EN
The paper was inspired by the hitherto published results concerning provision of efficient assistance to visually impaired persons by means of acoustic and vibratory signals. The aim of the auditory training is to shorten the time necessary for execution of auditory information processing, sensibilize blind persons to differences in sounds and teach them to focus auditory attention on small differences in parameters of acoustic waves, in order to achieve independent and correct interpretation of environment by hearing and listening. The basic concept of the auditory training addressed to blind or visually impaired children and teenagers is presented in detail. Preliminary verification of the effectiveness of training of young adults without vision impairments has not shown statistically significant differences in performance before and after the training. Possible reasons for such an effect are pointed out and solutions are suggested.
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