Contents of issue 4, vol. 28 (2003)

  1. W. Rybicka, A. Sęk, Detection of the amplitude modulation for modulating signals characterised by different crest factors, Archives of Acoustics, 28, 4, 273-292
  2. K. Marasek, Large vocabulary continuous speech recognition system for Polish, Archives of Acoustics, 28, 4, 293-303
  3. M.A. Ibrahim, R.W. Melik, Optimized sound absorption of a rigid polyurethane foam, Archives of Acoustics, 28, 4, 305-312
  4. A. Nowicki, W. Secomski, J. Litniewski, I. Trots, P.A. Lewin, On the application of signal compression using Golay's codes sequences in ultrasound diagnostic, Archives of Acoustics, 28, 4, 313-324
  5. T. Powałowski, Z. Trawiński, L. Hilgertner, Ultrasonic examination of common carotid artery wall elasticity of persons with different stages of internal carotid artery atherosclerosis, Archives of Acoustics, 28, 4, 325-337
  6. O.P. Piddubniak, N.G. Piddubniak, Sound radiation by a hollow circular elastic cylinder rotated in water with a variable angular velocity, Archives of Acoustics, 28, 4, 339-354
  7. P. Miecznik, Z. Gołębiewski, On ultrasonic relaxation study of preferential solvation in quasi two-component aqueous solutions of amides and zinc salts, Archives of Acoustics, 28, 4, 355-370
  8. Chronicle, Report of the XXth Symposium on Hydroacoustics, Archives of Acoustics, 28, 4, 371-374
W. Rybicka, A. Sęk, Detection of the amplitude modulation for modulating signals characterised by different crest factors
Institute of Acoustics, Adam Mickiewicz University
Umultowska 85, 61-614 Poznań, Poland
e-mail: rywi@amu.edu.pl; oleksek@amu.edu.pl
This study is concerned with the detection of amplitude modulation (AM) of a tonal signal for modulating signals characterised by a different crest factor and a low frequency. The purpose was to show that the root-mean-square (RMS) value of the modulating signal is not a sufficient measure of the modulation perceived by listeners. In the first experiment, using the 2AFC method with an adaptation procedure, the AM detection thresholds were determined for a 1-kHz tone modulated with 3-component harmonic complexes, the components of which had the same amplitudes. The starting phases of the complexes were chosen arbitrary to obtain the highest (2.44) and the lowest (1.89) values of the crest factor of the same root-mean-square values. The fundamental frequencies of the modulator were 1, 2 Hz and 4 Hz. The AM thresholds gathered for these modulators were characterized by a certain scatter that makes impossible the drawing of any conclusion concerning the influence of the crest factor on those thresholds.
Therefore in the second experiment psychometric functions were determined for the detection of AM using the same carrier and modulators. However, the results of this experiment did not provide unambiguous evidence for a statistically significant effect of the crest factor on the psychometric functions and the AM threshold values. Since the modulators used in the first two experiments were characterised by too small differences in the crest factor, the modulating signal in the third experiment was a harmonic complex consisting of ten pure tones of the same amplitude. The starting phases of all components were chosen so as to obtain signals characterised by the highest (4.47) and the lowest (1.58) crest factor. For these modulating signals, the probability of AM detection was found to depend significantly on the crest factor, i.e. the detection of the AM was considerably easier when a modulating waveform characterised by the highest crest factor was used.
The results of this experiment suggested that, at least for the low-frequency modulator, the description of the AM thresholds by means of the RMS values of the modulator is somehow misleading and does not express properly the abilities of the auditory system to detect low-frequency amplitude changes. It has been also suggested that for a modulating signal of a high crest factor the listeners can follow the amplitude changes over time only when the changes are slow enough, i.e. when sidebands produced by the amplitude modulation are not resolved in the auditory periphery.


K. Marasek, Large vocabulary continuous speech recognition system for Polish
Polish-Japanese Institute of Information Technology
Koszykowa 86, 02-008 Warszawa, Poland
kmarasek@pjwstk.edu.pl
This paper describes the development of the LVCSR (Large Vocabulary Continuous Speech Recognition) system for Polish. All system components have been built from scratch: grapheme-to-phoneme converter, language models and acoustic models. Test results for twenty thousands word vocabulary continuous speech recognition (read sentences) are given. The system can be used as a basis for application oriented continuous speech recognition.


M.A. Ibrahim, R.W. Melik, Optimized sound absorption of a rigid polyurethane foam
National Institute for Standards (NIS)
El-Haram-Giza, Egypt
In this study, cast panel received as sound insulator was implemented as sound absorber. The panel is composed of prepainted metal skins with a rigid self extinguishing polyurethane foam. For the achievement of such material as sound absorber, holes are uniformly drilled in the sample to allow relatively easy access of sound to the interior structure. Using the two microphone impedance measurement tube, the sound absorption coefficient was studied for samples of different, coverings, opening pores (2 mm, 3 mm), open areas (0.04, 0.16), and at air space depths: 0, 5, 10, 20 and 40 mm from the reflected wall. The normalized acoustic impedance was also studied. The results revealed that when the sample was uniformly drilled with pores of opening 2~mm each to have 0.16 mm open area, and positioned at air space depth (5 mm), it showed optimum sound absorption greater than 0.80 in the frequency range from 700-1600 Hz. In dealing with noise reduction, this absorption gives, 6.9 dB drop in noise level.


A. Nowicki*, W. Secomski*, J. Litniewski*, I. Trots*, P.A. Lewin**, On the application of signal compression using Golay's codes sequences in ultrasound diagnostic
*Institute of Fundamental Technological Research
Polish Academy of Sciences
Świętokrzyska 21, 00-049 Warszawa, Poland
**Drexel University, Philadelphia, PA
The issue of maximizing penetration depth with concurrent retaining or enhancement of image resolution constitutes one of the time invariant challenges in ultrasound imaging. Concerns about potential and undesirable side effects set limits on the possibility of overcoming the frequency dependent attenuation effects by increasing peak acoustic amplitudes of the waves probing the tissue. To overcome this limitation a pulse compression technique employing 8 bits Complementary Golay Code (CGS) was implemented at 4 MHz. In comparison with other, earlier proposed, coded excitation schemes, such as chirp, pseudo-random chirp and Barker codes, the CGS allowed virtually side lobe free operation. Computer simulation results for CGS pulse compression are presented. Next, the images of RMI tissue phantom generated by those two excitations schemes are presented. Identical peak power conditions in the experimental setup were implemented with the earlier mentioned 8 bits CGC and 2 periods tone burst. Experimental data indicate that the quality of CGS images is comparable to that acquired using conventional pulse imaging. CGS exhibited signal-to-noise ratio (SNR) gain of 9.6 dB with the axial resolution being virtually the same for both transmitting schemes.


T. Powałowski*, Z. Trawiński*, L. Hilgertner**, Ultrasonic examination of common carotid artery wall elasticity of persons with different stages of internal carotid artery atherosclerosis
*Ultrasonic Department, Institute of Fundamental Technological Research
Polish Academy of Sciences
Świętokrzyska 21, 00-049 Warszawa, Poland
**Department of General and Thoracic Surgey
Medical University of Warsaw
Banacha 1a, 02-097 Warszawa, Poland
Ultrasonic methods were used in this study to examine the association between the common carotid artery (CCA) wall elasticity and the atherosclerosis stage in the internal carotid artery (ICA). The degree of stenosis determined ultrasongraphically was used as an indicator of the atherosclerosis stage in the ICA. The examined persons were 45 to 80 years old. They had no arterial hypertension, diabetes mellitus and were not smokers. A comparative study was carried out for cases with ICA atherosclerosis (66 arteries) and without ICA atherosclerosis (61 arteries). In both groups there were persons without and with hypercholesterolemia, which according to our studies had no significant influence on CCA wall elasticity. The CCA wall elasticity was determined by the stiffness coefficient alpha and the distensibility coefficient DC based on ultrasonic measurements. The influences of age and arterial blood pressure on the CCA wall elasticity were taken into account in the analysis. The study revealed a significant decrease of the CCA wall elasticity in the case of patients with atherosclerosis compared with persons without atherosclerosis, and showed a significant correlation between the increase of the ICA stenosis degree and the decrease of CCA wall elasticity.


O.P. Piddubniak, N.G. Piddubniak, Sound radiation by a hollow circular elastic cylinder rotated in water with a variable angular velocity
Faculty of Process and Environmental Engineering
Technical University of Łódź
Wólczńska 213/215, 90-924 Łódź, Poland
and
Institute of Computer Technology, Automatics and Metrology
National University "Lviv Politechnika"
Bandery 12, 79-046 Lviv, Ukraine
e-mail: piddub@wp.pl
In this paper the sound radiation from an elastic circular cylinder of infinite length rotated with a non-uniform angular velocity in water is studied. The cylinder is empty inside. Exact solutions of the equations which describe the hydroelastic interaction are obtained using the Fourier transform over time. Numerical examples show that the spectral structure of the sound radiation from an elastic tube is more complicated than that of a solid cylinder. In particular, the resonances of this structure are essentially dependent on the thickness of the rotating object and are subject to the phenomena of dispersion.


P. Miecznik, Z. Gołębiewski, On ultrasonic relaxation study of preferential solvation in quasi two-component aqueous solutions of amides and zinc salts
Institute of Acoustics, Adam Mickiewicz University
Umultowska 85, 61-614 Poznań, Poland
To investigate the effect of preferential solvation, the ultrasonic attenuation (2-50 MHz) and velocities (3 MHz) in ZnCl2 and 2-chloroacetamide (ClCH2CONH2) solutions in water and its quasi-binary mixtures of the ratio (ZnCl2 + ClCH2CONH2): H2O = 1:55 at 298.15 K have been measured. The creation of specific complexes in the ClCH2CONH2 - H2O - ZnCl2 system have a relaxational character which, within the measurements of the ultrasonic absorption in the frequency range 2-50 MHz, have been observed. On the base of these properties, the kinetic and dynamic parameters of the observed relaxation have been calculated. To bring into relief the influence of the Cl atom in the 2-chloroacetamide molecules for the complexation process, also the system AA - H2O - ZnCl2 has been investigated. The next step of searching was the investigation of the system of CHAA - H2O - ZnBr2, to reduce the influence of the Cl atom within the ZnCl2 molecule in the complexation process. As the results, the observed relaxation processes have been attributed to the creation and disintegration of the following complexes: Zn(H2O)2(CHAA)42+ and Zn2+(H2O)3(CHAA)Cl2-.


Chronicle, Report of the XXth Symposium on Hydroacoustics
Jurata, May 27-30, 2003, Poland
Symposium on Hydroacoustics The XXth Symposium on Hydroacoustics was organized under the aegids of:
  • International Commission for Acoustics (ICA)
  • European Acoustics Association (EAA)
  • Polish Acoustical Society (PAS)
  • Acoustical Society of America (ASA)
  • The XXth Symposium on Hydroacoustics was organized by:
  • Gdańsk University of Technology
  • Polish Naval Academy in Gdynia
  • Scientific Committee: Prof. Eugeniusz Kozaczka - chairman
    Organizing Committee: Prof. Roman Salamon - chairman
    The Symposium programme included invited lectures, contributed papers and posters covering major research fields of hydroacoustics. All contributed papers submitted to the Scientific Committee were reviewed. All accepted papers were published in the Annual Journal "Hydroacoustics".
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