Contents of issue 2, vol. 30 (2005)

  1. M. Niewiarowicz, J. Czajka, E. Hojan, Investigations on the angle of directional hearing acuity, Archives of Acoustics, 30, 2, 147-157
  2. E. Hojan, H. Fastl, J. Malenda, D. Hojan-Jezierska, Investigations into speech intelligibility in the presence of different masking noises for hearing aids with variable attack and release times, Archives of Acoustics, 30, 2, 159-171
  3. J. Kociński, A. Sęk, Speech intelligibility in various spatial configurations of background noise, Archives of Acoustics, 30, 2, 173-191
  4. P. Dziechciński, Comparison of digital loudspeaker - equalization techniques, Archives of Acoustics, 30, 2, 193-216
  5. A. Perelomova, Modes and projectors of the viscous non-uniform flow. Heating caused by an acoustic beam between two parallel plates, Archives of Acoustics, 30, 2, 217-232
  6. E. Danicki, Acoustic sniper localization, Archives of Acoustics, 30, 2, 233-245
  7. E. Douka, B. Polyzos, A. Trochidis, Acoustic emission from a dislocation kink accelerated by an external force, Archives of Acoustics, 30, 2, 247-253
  8. Z. Ranachowski, E. Gondek, P.P. Lewicki, A. Marzec, Investigation of acoustic properties of compressed wheat bran flakes, Archives of Acoustics, 30, 2, 255-265
  9. Chronicle, 33-th Winter School on Vibroacoustical Hazards Suppression, Archives of Acoustics, 30, 2, 267-271
  10. Chronicle, The XIVth Conference on Acoustical and Biomedical Engineering 2005, Archives of Acoustics, 30, 2, 273-288
M. Niewiarowicz*, J. Czajka*,**, E. Hojan**, Investigations on the angle of directional hearing acuity
* Poznań University of Medical Sciences
Department of Otolaryngology
Przybyszewskiego 49, 60-355 Poznań, Poland
e-mail: niewiaro@amp.edu.pl
** Adam Mickiewicz University, Institute of Acoustics
Umultowska 85, 61-614 Poznań, Poland
e-mail: hojanaku@amu.edu.pl
(received September 23, 2004; accepted January 27, 2005)
This article presents results of investigations of the angle of directional hearing acuity (ADHA) as a measure of the spatial hearing ability. A modified method proposed by Zakrzewski has been used -- ADHA values have been determined for azimuths in the horizontal plane at the height of the listener's head. Application of different acoustic signals - sinusoidal signals (pure tones), 1/3 octave noise, and amplitude modulated 1/3 octave noise, helped to reveal significant differences in ADHA values for individual signal types. A better localization of the sound source for noise type signals than those for sinusoidal signals has been found. Furthermore, smaller differences in the perception of noise signals compared with differences in the perception of sinusoidal signals were recorded for individual listeners. The best localization was stated for the azimuth 0o and the worst for the azimuth 90o and 270o.
Key words: sound source localization, angle of directional hearing acuity, amplitude-modulated 1/3 octave band noise.

E. Hojan*, H. Fastl**, J. Malenda*, D. Hojan-Jezierska***, Investigations into speech intelligibility in the presence of different masking noises for hearing aids with variable attack and release times
* Adam Mickiewicz University, Institute of Acoustics
Umultowska 85, 61-614 Poznań, Poland
** TU Munich, Chair for Man-Machine-Communication, Germany
*** Medical Academy of Poznań, Chair of Biophysics, Poland
(received September 21, 2004; accepted March 15, 2005)
People with hearing impairments experience a reduction in speech intelligibility in noisy surroundings. The extent of this reduction depends on the degree of impairment in the temporal resolution of the patient's ear, too.
The change of the speech intelligibility of hearing-impaired people was investigated in the presence of different masking noises, especially when using hearing aids with adjustable attack (AT) and release (RT) times within same frequency bands.
Key words: speech intelligibility, masking noises, hearing aids, attack and release times.


J. Kociński, A. Sęk, Speech intelligibility in various spatial configurations of background noise
Adam Mickiewicz University, Institute of Acoustics
Umultowska 85, 61-614 Poznań, Poland
e-mail: jen@amu.edu.pl, oleksek@amu.edu.pl
(received May 5, 2004; accepted January 27, 2005)
This study is concerned with the influence of spatial separation of disturbing sources of noise on the speech intelligibility. Spatial separation of speech and disturbing sources without changing their acoustic power may contribute to the significant improvement in the speech intelligibility. This problem has been recently analysed in many papers [1-5]. These works have confirmed an important role of the spatial configuration of sources. However, there have been no work investigating this problem for nonsense words (logatoms) that may provide more rigorous tests of this phenomenon. Moreover, this problem has not been analysed for Polish speech. It is important to emphasize that the acoustic and phonetic properties of Polish speech are somewhat different from those of English one. Therefore, the attempt to investigate the influence of the spatial separation of sound sources was made in this study. In the situation with more than one spatially separated disturbances, there may occur a so-called spatial suppression phenomenon, that is ``mutual suppression'' of disturbing sounds in the auditory system that brings about an increase in the speech intelligibility. This phenomenon is also called the spatial unmasking of speech [5, 6].
The research consist in determination of the speech intelligibility in the presence of one or two statistically independent speech-shaped noise sources varying in configuration. Only two pairs of the spatial configurations were investigated.
Character of the dependences obtained in the study implies that the spatial suppression occurs in certain configurations of sources only. This effect brings about an increase in the speech intelligibility and can be explained on the basis of the binaural masking level difference (BMLD). It seems then that the BMLD may be a more general phenomenon and includes not only difference in the detection threshold of a pure tone masked by noise but also the improvement in the speech intelligibility, while speech is presented at the background of disturbing signals.
Key words: speech intelligibility, speech perception, spatial separation, spatial suppression.


P. Dziechciński, Comparison of digital loudspeaker - equalization techniques
Wrocław University of Technology, Institute Telecommunications and Acoustics
Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
e-mail: pdziechc@zakus.ita.pwr.wroc.pl
(received July 19, 2004; accepted January 27, 2005)
An overview of digital equalization techniques for loudspeaker systems is presented. The known algorithms are systematized and modified. Equalization is effected by a single digital filter for the on-axis loudspeaker response. Besides classical FIR and IIR digital filter structures, their warped versions (WFIR and WIIR) are used to build equalization systems. Equalizers of different types are compared with regard to efficiency. Also information about objective and listening-test assessments of the quality of equalization obtained by the different equalizers is provided. Besides the equalizer quality assessment techniques know from the literature, new techniques, which better represent the properties of the human auditory system, are proposed. For the new techniques better agreement between the objective results and the listening-test ratings was obtained. On the basis of objective assessments of 32 equalization systems carried out for two stereophonic pairs of loudspeaker systems algorithms yielding the best results for each of the tested filter structures (FIR, IIR, WFIR and WIIR) were selected and evaluated by listening tests.
Key words: equalizer, digital filter, loudspeaker system.


A. Perelomova, Modes and projectors of the viscous non-uniform flow. Heating caused by an acoustic beam between two parallel plates
Gdańsk University of Technology
Narutowicza 11/12, 80-952 Gdańsk, Poland
e-mail: anpe@mif.pg.gda.pl
(received February 02, 2004; accepted January 27, 2005)
The modes of the thermoviscous flow over a strongly non-uniform background have been obtained. Corresponding matrix projecting operators that decompose every mode, or every possible type of the hydrodynamic motion, from the overall field perturbation have been written in the explicit form. Projecting has been used in order to get dynamic nonlinear equations. Acting by the projector corresponds to the entropy mode of the system of conservation laws, while the acoustic mode which is supposed to be dominating yields in the governing equation for the acoustic heating caused by the attenuated acoustic beam. An example of calculations of heating in the viscous flow between two parallel plates has been given.
Key words: non-uniform thermoviscous flow, boundary layer, acoustic heating.


E. Danicki, Acoustic sniper localization
Institute of Fundamental Technological Research
Polish Academy of Sciences
¦więtokrzyska 21, 00-049 Warszawa, Poland
e-mail: edanicki@ippt.gov.pl
(received October 29, 2004; accepted March 15, 2005)
Acoustic signals of small arm's fire, the muzzle blast and the shock wave generated by a supersonic bullet in air, are difficult to mask and can be exploited for localization of the hidden sniper. This paper presents the system of acoustic measurements, based on a number of both directional and omnidirectional microphones detecting the shock wave only, yielding exact solution for the sniper direction in spite of certain errors in the directional measurements. The system has a self-correcting ability concerning the sound directional measurements which contributes to the system technical feasibility. Auxiliary muzzle blast measurements would yield the sniper position.
Key words: shock waves, measurements.


E. Douka*, B. Polyzos**, A. Trochidis**, Acoustic emission from a dislocation kink accelerated by an external force
* University of Thessaloniki, School of Engineering, Mechanics Division
Thessaloniki 54124, Greece
** University of Thessaloniki, School of Engineering, Physics Division
Thessaloniki 54124, Greece
e-mail: trohidis@gen.auth.gr
(received June 18, 2004; accepted March 15, 2005)
The emission of elastic waves from a dislocation kink accelerated by a constant external force is presented. The dynamics of the dislocation kink interacting with longitudinal acoustic waves is described by a sine-Gordon--d'Alembert system, i.e. a sine-Gordon equation nonlinearly coupled with the d'Alembert wave equation. Within the framework of this model, the evolution of velocity of the dislocation kink altered by the applied force is determined, allowing for mechanical couplings. The total energy radiated from the dislocation kink and its spectral composition is calculated numerically and analytically. Computer simulations are presented, which graphically illustrate the analytical considerations and model the acoustic radiation.
Key words: acoustic emission, dislocations dynamics, nonlinear waves.


Z. Ranachowski*, E. Gondek**, P.P. Lewicki**, A. Marzec**, Investigation of acoustic properties of compressed wheat bran flakes
* Institute of Fundamental Technological Research
Polish Academy of Sciences
¦więtokrzyska 21, 00-049 Warszawa, Poland
e-mail: zranach@ippt.gov.pl
** Warsaw Agricultural University (SGGW), Faculty of Food Technology
Nowoursynowska 166, 02-787 Warszawa, Poland
(received November 5, 2004; accepted March 15, 2005)
The authors of this paper analysed Acoustic Emission (AE) signal generated during compression test of wheat bran flakes. Three AE descriptors were applied to process the results of the tests: counting of total number of EA events, average event duration and partition power spectrum slope. It was found that the presented descriptors correlate with the measured level of specimen structural moisture and one descriptor can be used in investigation of the effect of the loss of the perceived crispness in moistured product. The described methods of data processing can be applied to food product quality assessment procedures.
Key words: food texture evaluation, crispness evaluation, acoustic emission.


Chronicle, 33-th Winter School on Vibroacoustical Hazards Suppression
Ustroń, 28-th February - 3-th March 2005
The 33rd WS on VHS, as an every-year conference organized by the Upper-Silesian Division of the Polish Acoustical Society and the Institute of Physics of the Silesian University of Technology, has taken place between the 28th of February and the 3rd of March 2005 in Ustroń. At the this year conference polish acousticians involved in scientific investigations and the design activity of environmental protection have met. During the School, the participants had an opportunity to present information on devices, materials and regulations concerning technical and environmental acoustics. The language of conference was Polish.
Totally 47 participants have contributed to the 33rd School. There were 23 lectures delivered during the School. Their subjects were in agreement with the character of the School. The subjects were broad and included physical acoustics, environmental acoustics, room acoustics, architectural acoustics and acoustical metrology. As usuallyl, the time before lunch has been spent on recreation and winter sports. The conference meetings took place after lunch and in the evening.
The conference organizers published ?Materials of the XXXIII Winter School on Vibroacoustical Hazards Suppression? (160 pages, in Polish) that contain most of the lectures presented.


Chronicle, The XIVth Conference on Acoustical and Biomedical Engineering 2005
Zakopane, 1st - 5th of June, 2005
Ryszard Panuszka, Marek Iwaniec
AGH University of Science and Technology
Structural Acoustics and Intelligent Materials Laboratory
Al. Mickiewicza 30, 30-059 Kraków, Poland
The XIVth Conference on Acoustical and Biomedical Engineering 2005 will be held in Zakopane from the 1st to the 5th of June, 2005. Since 1991 the conference has been organized every year in various places in the Polish Mountains such as Zakopane and Krynica. The 2005 Conference will take place in Hyrny Hotel at Zakopane, Piłsudski Street 20.
The conference is organized by the Kraków's Division of the Polish Acoustic Society and the Structural Acoustics and Intelligent Materials Laboratory at the School of Mechanical Engineering and Robotics, AGH University of Science and Technology. The Conference is organized under the auspices of the Rector of the University of Science and Technology AGH in Kraków, Prof. Ryszard Tadeusiewicz. The Organizing Committee is chaired by Prof. Ryszard Panuszka. The Conference will be opened by the Dean of the Faculty of Mechanical Engineering and Robotics Prof. Włodzimierz Kowalski.
The main focus of the annually held conferences is the inspiring and development of acoustical engineering methods in various branches of science and human health issues. The Conference has an interdisciplinary character and integrates researchers who represent technical sciences, physics and medical studies.
Tutorials, lectures and working meetings are regular features of the conference, along with culture programs related to the beauty and folklore of the Tatra region. Every year the Conference offers special opportunities for students and young researchers to share and exchange information with more experienced scientists. Participants who attend the meetings regularly can find personal contacts and rewarding experience.
At each meeting invited and contributed papers and poster presentations reflect the diversity of the membership interests. The scope of this year Conference will cover topics of acoustical engineering like: radiation of sources, speakers and headphones designing, home theatres designing, energy flow in structures, smart structures & control of sound flow and vibration energy, prediction of acoustic fields, environmental noise protection, acoustical emission, technologies for acoustic reproduction of sound, DSP in acoustical engineering. Papers focused on waves and effects on human beings and environment deal with subjective and objective methods of evaluation of loudspeakers, radiation/headphone properties, music and human, low frequency waves and vibrations, electromagnetic waves, methods of protection, effects of waves and vibrations on human.
The plenary lecture will be given by Jim Hunter from Klipsch Audio Technologies on new trends in development and research in electro acoustics. The lecture will focus on home theatres design and technologies of sound reproduction on the basis of the experience of the Klipsch Audio Company. Prof. Jan Adamczyk from the AGH University of Science and Technology will discuss the problem of acoustical signal processing and audio decoders. Dr. Ewa Skrodzka will present the goals of modal analysis and BEM applications to research on the relation between vibration and radiation of loudspeakers. Prof. Ryszard Panuszka will present a paper on "Acoustical Climate at Home by Design Solutions of Frank Lloyd Wright". Prof. Marian Dobry will explain a method of experimental verification of power distribution and energy flow on the example of two biological-mechanical systems: Human - Impact Drill and Human - Breaker, Dr. Lucyna Leniowska will present a mathematical model of an actively attenuated circular plate included in the internal dissipation and the influence of an acoustic wave radiated by the plate on its vibrations. Prof. Witold Rdzanek will discuss a new approximation of sound radiation of an annular plate. Prof. Michael P. Wnuk will present studies of the influence of rheological and fracture properties on acoustic emission of advanced aerospace materials.
The contributed papers cover a wide area of acoustical investigations, present diversified approaches to problems which have been considered and show various methodological attitudes undertaken to solve practical and theoretical tasks.
The conference is bilingual, so traditionally the languages of the conference are Polish and English. The Conference is divided into three panels: "Acoustical Engineering", "Waves and Effects on Human and Environment" and "Biomedical Engineering". The participants can take part in the whole conference or in a single part.