Current trends of the works on acoustics presented at the XLVI Open Seminar on Acoustics OSA'99

The XLVI Open Seminar on Acoustics was held in Zakopane
from the 14th to the 17th of September 1999. It was organized by Cracow's
Section of the Polish Acoustic Society, the Laboratory of Structural Acoustics
and Intelligent Materials, the Faculty of Mechanical Engineering and Robotics of
the Academy of Mining in Cracow and the Committee on Acoustics of the Polish
Academy of Sciences. The number of participants was 175. 118 papers were
presented. The honorary president was Prof. Ignacy Malecki. Prof. Zbigniew Engel
was chairman of the Scientific Committee and the Organizing Committee was
chaired by Prof. Ryszard Panuszka. The Seminar was opened by the plenary lecture
of Prof. Ignacy Malecki devoted to the application of acoustic emission in
engineering materials. The examples of new applications presented in his lecture
concerned the monitoring of the technology of ceramics, the investigation of
variations in the structure and microstructure of those materials caused by
thermal shocks and the monitoring of the behaviour of constructions under
conditions close to those prevailing during their long term exploitation as well
as the analysis of mechanical and thermo-mechanical parameters in that
plasticity and pseudoplasticity effects have been considered. At the beginning
of the proceedings in each section a plenary lecture was given. All in all,
seven lectures were delivered. Prof. Antoni Jaroszewski discussed the perception
effects of an acoustic injury caused by exposure to music sounds with reference
to loudness, height discrimination and the frequency and time resolution.
Musicians are particularly subject to those injuries. Significant lasting,
selective and high-frequency losses in their hearing were found. They indicate
that the hearing protection of this group of people is insufficient. Prof.
Eugeniusz Kozaczka focused his lecture on some problems of the non-linear
effects connected with the generation and propagation of elastic waves in water,
on non-linear properties of a medium as well as on making use of those
properties in parametric sources of acoustic waves. Prof. Adam Lipowczan
characterized the usefulness of modern GIS and GPS techniques in the solution of
problems connected with the dangers of vibroacoustic effects to the environment.
Those techniques, linking computer maps with data bases, offer new research
methods and applications to the study of the propagation of noise and mechanical
vibrations in the environment. Dr. Henryk Łopacz presented the possibility of
the simulation of audio monitoring in physical as well as in virtual rooms. The
simulation of audio monitoring conditions is realized by a convolution of pulse
response for a given transmission way and the test signal. In the algorithms
presented, the influence of room dimensions, the locations of transmitting and
receiving points and the attenuating properties of the room can be taken into
account. Profesor Stefan Weyna discussed the analysis of measurements of the
vector effects of an acoustic wave represented as sound intensity in the
acoustic field of real sources. The results presented concerned measurements of
acoustic phenomena occurring in the near field and in small limited areas. The
application of a broad-band three-way system to the identification and
classification of sea fish shoals was presented by Professor Manell Zakharia.
The main construction problems of this device concern the transducers, the
levels of the transmitted and received signals, the directivity and impedance
variations in the whole frequency region. For a correct working of the device,
the algorithm of identification of the fish species is also essential. It was
shown that neuron nets can be applied to this end. The device discussed is
characterized by a high linearity and a better estimation of the fish size. The
identification of the fish species is based only on the characteristic
frequencies of the received echo.