The aim and purpose of this thesis is to investigate the impact of sudden and unexpected loudness changes, compared to the average loudness of a soundscape, on people's concentration and change in perception. The doctoral hypothesis had been based on my own observations and experiences. A matter of adapting to a certain soundscape, if it is not too loud, but noticing distraction caused by sudden and unexpected loudness changes while performing concentration demanding tasks has proven to be an interesting study. A real question was how individual sounds, which in a certain way "do not belong" in a specific soundscape, determine how the complete soundscape could be perceived as pleasant or unpleasant and whether the sound that was not expected, even if it were relatively quiet, distracted or even disturbed us in comparison to the soundscape that we had became accustomed to. Therefore, the idea is to study different soundscapes while focusing on sudden and unexpected loudness changes. The dissertation research participants were tested by performing a “task” which had been constructed in a way to substitute people’s everyday tasks which require a minimal level of concentration. The subjects were performing this task while listening to various soundscape recordings.The study had been carried out with natural sounds (natural soundscapes) and as a result certain objective parameters were determined that form the soundscape evaluation model used for estimating the soundscape pleasantness or similarly the soundscape unpleasantness. A classification of attributes describing the subjective experience of a soundscape had also been carried out. The results showed which of the attributes are relevant to adequately describe a soundscape and to define new objective parameters determining the distraction factor of a certain soundscape. Most importantly, a model which calculates the distraction factor had been established and then confirmed on an uninvestigated and independent soundscape. The second dissertation chapter clarifies the concept of a soundscape, the most common classification of soundscapes, recording methodology and potential analysis, while also describing all selected and recorded soundscapes. The third and fourth chapters deal with parameters most commonly used for describing and evaluating soundscapes. Chapter three describes the objective acoustic parameters while chapter four deals with the subjective parameters specific to the evaluation and classification of soundscapes. The fifth chapter presents a detailed analysis and the statistical processing of the obtained results, while the sixth chapter describes further research with short sound signals (by previous studies described as distracting and annoying) that were inserted into the most pleasant soundscape (proven by previous studies) and finally the analysis of the related results. The aforementioned analysis shows the most common reasons why a certain sound would be perceived as annoying and distracting. A synthesis of the results of subjective tests and objective acoustic parameters had been carried out in the seventh chapter. The eighth chapter describes the development of the model used for calculating the distraction factor of a soundscape and the model testing on a "new", independent soundscape. It is important to emphasize that the methodology and respected postulates of psychology and statistics were fully complied with in all the research, whereas otherwise the findings proven on a representative sample could not be applied to the population.