The acoustic properties of classrooms for verbal communication are characterized by reverberation time and the speech transmission index. From the teachers’ point of view, it is also important what voice intensity is necessary to ensure an acceptable level of communication. In rooms with shorter reverberation time, background noise is reduced, which enables a reduction in the teacher''s voice intensity, without a decrease in the quality of verbal communication. This is due to the fact that speakers unconsciously and without thinking adjust the volume of their voice, so that it is several decibels higher than the level of background noise (the so-called Lombard’s effect). This article presents the results of research on determining the density distribution of sound pressure level in the classroom, from which the level of the teacher’s voice and background noise are determined.

Exploitation of open-pit mines of minerals constitutes vibroacoustic hazards for their workers and inhabitants living near such establishments. Noise, one of the main harmful factors in the working environment, is a threat to the external environment, particularly when mining works are carried out near residential areas or reserves. The quarry industry is connected with many noisy activities: drilling, blasting, crushing rocks, aggregate screening and transporting mineral materials. Operators of mining and transport machines, service personnel and technical inspectors are exposed to noise. Occupational diseases, distorted speech intelligibility among workers and accidents at work result from exceeded noise levels.

Through identification of the most endangered type of work and a course of the most common accidents at work, the statistical data analysis of accidents at work enables to adequately orientate efforts and to shape preventive actions. This article presents the results of analysis of the most common accidents at work among metal workers professional group, as well as related occupations.

Quantitative and qualitative assessment of microbial contamination from archives and libraries is essential in preventing microbiological hazards for the durability of collections and personnel''''s health. The aim of this study was to determine the level and type of microbial contamination of the air and on surfaces in selected archives and library premises. Moreover, isolated fungi were classified due to potential harm for personnel. The study quantitatively showed different numbers of microorganisms in the air in archives and libraries, depending on the specific type of room and collections. Bacterial contamination was at a low level, and there was an increased degree of fungal contamination. Frequency of the isolation of particular microorganism strains made it possible to select representative species of archives and library premises Cladosporium (C. herbarum, C. macrocarpum), Penicillium (P. carneum P. crustosum), Rhizopus nigricans, Aspergillus versicolor, Bacillus pumilus, Micrococcus spp., Staphylococcus lentus. Fungi with high risk - BSL-2: Aspergillus flavus, Aspergillus terreus and Paecilomyces variotii were identified.

The paper presents the test results of the influence an air relative humidity (RH) and a suitable water contents in textile materials on their ability to maintain of the electrostatic charge. It was proved, that the basic range of textile products (denim, flannel, wool, polyester fabric) after conditioning at 23 °C and RH (25-80)% reaches the equilibrium state with the absorbed water in the time of no longer than 10 hours. The largest change (increase) of the electrical resistivity for the tested textiles amounts to the 3 magnitude orders passing from the dry state to the equilibrium state in 50% RH.
It was found, that for the tested kind of textile materials, the 12 h time of the conditioning is entirely enough and the requirement of the considerably longer conditioning times, as in some standards, is groundless.
It was stated, that knowledge of the RH influence range on the resistivity of the textiles makes possible to adjust the assessment criteria of their anti-static properties for the easy reached in practice “standard”-RH conditions [t = (23±2) °C; RH (50±5)%], which not require of expensive equipments and complicated procedures.