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.

One of the main issues of design process of HVAC systems and ventilation ducts in particular is correct modelling of coupling of the flow field and acoustic field of the air flowing in such systems. Such a coupling can be modelled in many ways, one of them is using linearised Euler equations (LEE). In this paper, the method of solving these equations using finite element method and open source tools is decribed. Equations were transformed into functional and solved using Python language and FEniCS software. The non-reflective boundary condition called buffer layer was also implemented into equations, which allowed modelling of unbounded domains. The issue, influence of flow on wave propagation, could be adressed using LEE equations, as they take non-uniform mean flow into account. The developed tool was verified and results of simulations were compared with analytical solutions, both in one- and two-dimensional cases. The obtained numerical results are very consistent with analytical ones. Furthermore, this paper describes the use of the developed tool for analysing a more complex model. Acoustic wave propagation for the backward-facing step in the presence of flow calculated using Navier-Stokes equations was studied.

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