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1
Content available Preliminary Study on the Influence of Headphones for Listening Music on Hearing Loss of Young People
Dobrucki A. B., Kin M. J., Kruk B.
Archives of Acoustics
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2013
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Vol. 38, No. 3
383--387
EN
The paper presents results of hearing loss measurements provided for 81 young people (from 16 to 25 years old). The main aim of the work was to find the influence of headphones of the types used (closed, semi-open, open and in-ear) on the hearing losses. The first part of the research was to answer questions about the influence of: time of listening, loudness of music, other noise exposures as well as the type of the headphones used. It turned out that all factors mentioned above influence thresholds of hearing but the found dependencies are not explicit. The greatest hearing losses were observed for people who work as sound reinforcement engineers and, moreover, no influence of the headphone types was found for them. It turned out that the use of in-ear headphones causes the greatest hearing losses for some subjects (thresholds shifted up to about 20 dB HL at 4 kHz). The daily time of a listening also affected the hearing thresholds. It was found that for users of in-ear and close headphones, an average time of musical exposure of three hours causes the hearing loss of 10-15 dB HL at higher frequencies. The use of open as well as semi-open headphones has no influence on the hearing damage. Thus it would be stated that these kinds are safety in use. Almost 15% of the investigated young people have their thresholds shifted up at higher frequencies, particularly at 4 kHz, which means that they have the first symptoms of a permanent hearing damage.
2
Content available remote Acoustic processes in RF excited CO2 laser plasma in pulse regime
Wojaczek D. A., Dobrucki A. B., Pliński E. F.
Optica Applicata
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2010
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Vol. 40, nr 1
143--153
3
Content available remote Acoustic mapping of the back-scattering interferometer signal in a CO2 laser
Wojaczek D. A., Chodorowski P., Dobrucki A. B., Witkowski J. S., Pliński E. F.
Optica Applicata
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2010
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Vol. 40, nr 4
909--919
EN
It is shown that a microphone placed in the laser plasma can be used for detection and observation of the optical phenomenon such as an optical feedback in a continuous wave regime of the laser operation. To observe the effect, a periodically moved external mirror has been used. The periodical changes of the optical beam intensity in the laser cavity generated changes in frequency and amplitude of the acoustic signal. In conclusion, the acoustic wave gives information about optical effects created in a waveguide CO2 laser.
4
Dependence of the head-related transfer function on pinna flare angle
Plaskota P., Dobrucki A. B.
Elektronika : konstrukcje, technologie, zastosowania
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2009
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Vol. 50, nr 3
19-21
EN
Head Related Transfer-Function (HRTF) describes the modification of the spectrum of acoustic wave arriving to the ear. The HRTF influences sound source localization by auditory system. It has been proved that individual properties strongly influence HRTF. Application of HRTF which is different for each individual decreases the ability of sound source localization by the listener during headphones sound projection. The aim of the paper is the study of influence of pinna flare angle on the HRTF shape.
PL
Funkcja Transmitancji Odniesiona dp Głowy (HRTF) opisuje modyfikację widma fali akustycznej docierającej do ucha. HRTF wpływa na lokalizację źródła dżwięku przez system słuchowy. Zostało udowodnione, że cechy osobnicze silnie wpływają, na HRTF. Zastosowanie HRTF, które jest różne dla każdego słuchacza powoduje pogorszenie zdolności lokalizacji źródła dźwięku podczas odsłuchu przez słuchawki. Celem pracy jest zbadanie wpływu kąta odchylenia małżowiny usznej na przebieg HRTF.
5
Content available remote Computational modelling of head-related transfer function
Dobrucki A. B., Plaskota P.
Archives of Acoustics
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2007
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Vol. 32, No. 3
659--682
EN
Measuring the Head-Related Transfer Function (HRTF) is an efficient method that takes into consideration the influence of the human body on the sound spectrum. The data base used in reproduction of the sound source position is built using the measurement results. The base is individual for each person, which makes it impossible to make a versatile base for all listeners. In this paper a numerical model of artificial head is presented. The model allows to determine the value of HRTF without making measurements. The model includes both geometrical and acoustical parameters. A method which is often used to determine the acoustical field parameters is the boundary element method, which was used to calculate the values of HRTF in this work. In the conclusion results of the calculations are presented and the correctness of the previous assumption made while constructing the geometric part of the numerical human head model is discussed.
6
Content available Application of the narmax method to the modelling of the nonlinearity of dynamic loudspeakers
Dobrucki A. B., Pruchnicki P.
Archives of Acoustics
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2001
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Vol. 26, no. 4
277-291
EN
The application of the NARMAX method to the modelling of the nonlinearity of dynamic loudspeakers is described. The principle of creating a polynomial representation of a model, the problems stemming from a too large number of model coefficients and the method of optimizing the model are presented. The method was tested on data from actual loudspeaker measurements. Different models are compared as regards their accuracy depending on the modelling parameters. Finally, the model characteristics are compared with the results of loudspeaker measurements performed by classical methods.
7
Content available remote Adaptation of image reconstruction algorithm for purposes of ultrasound transmission tomography (UTT)
Dobrucki A. B., Opieliński K. J.
Archives of Acoustics
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2000
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Vol. 25, no. 4
395-422
EN
In this research, the convolution and backprojection method has been adapted for the purposes of image reconstruction in ultrasound transmission tomography (UTT). In particular, a complete computer algorithm enabling the use of different convolving and interpolation functions has been developed. A technique of reducing and scaling the tomographic measuring data to minimize the reconstruction errors is proposed. The convolution and backprojection method was optimized through a choice of a versatile convolving function and a simple interpolation function, and it was tested using simulated and actual tomographic measuring data. After reconstruction, good-quality images were obtained. It has been found that the number of measuring rays determines the resolution of an image, the accuracy with which the size of structures is imaged and the accuracy with which the image point values are reconstructed, whereas the number of measuring projections determines the dynamics and distortion of an image. Because of computation time and image blur, an optimum reconstruction grid size, according to the visualization quality criterion, should be chosen. The convolution and backprojection algorithm optimized in this research can be applied directly to the UTT visualization of the internal structure of objects as a distribution of local sound velocities in this structure, reconstructed on the basis of measurements of mean times of the passage of an ultrasonic wave through a cross-section of an object immersed in water, in a parallel ray projection geometry.
8
Content available remote Perception of mixed modulation for single components in harmonic complex for high modulating frequencies
Kin M. J., Dobrucki A. B.
Archives of Acoustics
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1998
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Vol. 23, no. 3
379-390
EN
Results and problems of perception of mixed modulation in a harmonic multitone are discussed. The experimental research was done for higher modulating frequencies (70 and 200Hz) and a 5-harmonics complex with fundamental frequency of 256Hz. The results indicated that for a modulating frequency of 70Hz, the perception of frequency modulation in the presence of the threshold values of the amplitude modulation is different from the perception of amplitude modulation in the presence of the threshold values of the frequency modulation. This means clearly that there are two mechanisms of the perception for these kinds of modulation.
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