Several methods can be applied for analyses of the acoustic field in enclosed rooms namely: wave propagation, geometrical or statistical analysis. The paper presents problems related to application of the boundary elements method to modelling of acoustic field parameters. Experimental and numerical studies have been combined for evaluation of acoustic impedance of the material used for the walls of a model room. The experimental studies have been carried out by implementing a multichannel measuring system inside the constructed model of an industrial room. The measuring system allowed simultaneous measurements of the source parameters -the loudspeaker membrane vibration speed, the acoustic pressure values in reception points located inside the model space as well as phase shifts between signals registered in various reception points. The numerical modelling making use of the acoustic pressure values measured inside the analyzed space allowed determination of requested parameters of the surface at the space boundary.

Acoustic eld in enclosed rooms in the low frequency range can be described by the wave model, based on solution of the wave equation. Solution to the wave equation for acoustic eld in the room can be obtained using numerical procedures, e.g. the boundary elements method. Determination of acoustic impedance of the room walls surface material, based on the knowledge of the distribution of acoustic pressure amplitudes in the enclosed space, requires application of the inverse boundary elements method and gathering a proper set of input data. The paper presents the possibilities of analysis of acoustic properties for industrial-type rooms, by using inverse methods in the low frequency range.

The article constitutes the continuation of the works realized under the research project entitled: The development of the method for marking and identication of the spots dangerous and of special importance for vision impaired persons in the big city with use of the wave-vibration markers. The consideration included the identication of the object (human), identication of the direction of movement (double barrier), wireless data transmission with the information on the dangerous area, stimulation of the vibration signal and the feedback of the system. This article presents the result of choice of the optimal solution regarding the installation of the system on the selected objects of the urban engineering and also presents the concept of the method of modelling of the shape of the zone that is used for marking of the dangerous spot.

The noise generated by different types of fans used in the turbomachinery industry is a topic that has been studied for many years. However, researchers are still looking for a universal solution to reduce noise while maintaining the performance of these machines. This paper, as a contribution to the research, presents the results of numerical investigations of an axial fan installed in a pipeline with a circular cross-section. In particular, the focus was on investigating the sensitivity of the sound power level to changes in selected design and operational parameters of this fan. The simulation studies used the unsteady Reynolds-averaged Navier–Stokes (URANS) approach and the Ffowcs Williams–Hawkings (FW-H) analogy implemented in Ansys Fluent.

The area of environmental protection concern minimises the impact that technical objects have on the environment. Usually the most effective way of protecting the environment is to influence the source of the problem. For this reason studies are conducted to modify the construction of machines, power machines in particular, so as to minimise their impact on the environment.In the case of environmental protection from noise it is most convenient to carry out measurements in an anechoic chamber. Unfortunately, this is possible only in very limited circumstances. In all other cases measurements are performed using an engineering method or the survey method, both of which are described in the standards and by taking into account the so-called environmental corrections. The obtained results are burdened with greater error than those of measurements in an anechoic chamber. Therefore, it would seem advantageous to develop a method of obtaining similar and reliable results as those in an anechoic chamber, but in a reverberant field. The authors decided to use numerical modelling for this purpose.The main objective of this work is a comprehensive analysis of the numerical model of a laboratory designed for acoustic tests of selected power machines. The geometry of a room comprising an area of analysis is easy to design. The main difficulty in modelling the phenomena occurring in the analysed area can be the lack of knowing the boundary conditions. Therefore, the authors made an attempt to analyse the sensitivity of various acoustic parameters in a room in order to change these boundary conditions depending on the sound absorption coefficient.

This paper presents the conceptual design of tools integration for the dynamic creation of sound level distribution maps (acoustic maps) in a production hall with an employee position identification system. This solution allows for managing the working time of employees in a zone designated as dangerous. At the same time, it could eliminate the need to use personal dosimeters that do not accurately assess actual exposure to noise. The proposed method allows us to estimate the uncertainty assessment of human exposure to noise. Moreover, a large part of the solution is based on tools that do not require incurring licensing costs. The system is about to keep the simulation data of sound level distribution (acoustic maps) and time location of the employee in the database. The concept assumes the unification of a data storage system so that it could be possible to present it in any GIS system.

The paper presents a comparison of central processing unit (CPU) and graphics processing unit (GPU) performance in sound synthesis based on physical modeling. The goal was to achieve real-time performance with two-and three-dimensional finite difference (FD) instrument models. Two abstract instruments, a membrane and a block, were modeled and tested using a CPU and a GPU in the OpenCL framework to find a threshold of real-time model size. Two different algorithms were compared. With a parallelized algorithm, a middle-class GPU outperformed a top-class CPU by factor of 2.5 in 2D and by factor of 7.5 in 3D model. Synchronization issues in parallel GPU calculations were discussed and addressed. The results show that GPUs can significantly speed up real-time musical instrument simulations, allowing for developing more complex and realistic models.

Providing appropriate sound eld parameters in the listening area is very important. It often determines the possibilities of being able to use a facility. Assuming that the sound system is a linear object, it can be described by the impulse response. Unfortunately, it is not possible to designate a single impulse response for such a facility because it is a continuous system. Thus each path between the transmitter and the receiver has its own impulse response. Therefore, the authors have made an attempt to synthesize the impulse response for transmitterreceiver paths with suitable parameters of the sound eld in the neighbourhood of the receivers. A technical implementation of the presented synthesis will take place through introduction of additional sources. An experimental determination of the impulse response is relatively simple. The transient response can be numerically determined by using, for example, the nite element method or the boundary element method. Unfortunately, determining the impulse response through simulation of, e.g., planned objects, is much more dicult due to the high computational cost and the lack of precise data on the properties of the materials. For this reason, the authors used an energetic analogue of the impulse response, the echogram.