In the present study, we aimed to determine the changes of indoor radon concentrations depending on various environmental parameters, such as the outdoor temperature, relative humidity, and air pressure, in university building premises of different applications and heights. The environmental parameters and indoor radon concentrations in four different premises were measured each working day over an eight-month period. The results showed that the indoor radon levels strongly depended on the outside temperature and outside relative humidity, whereas the weakest correlations were found between the indoor radon levels and indoor and outdoor air pressures. The obtained indoor radon concentration and environmental condition correlations were different for the different premises of the building. That is, in two premises where the ventilation effect through unintentional air leakage points prevailed in winter, positive correlations between the radon concentration and outside temperature were obtained, reaching the values of 0.94 and 0.92, respectively. In premises with better airtightness, negative correlations (R = −0.96 and R = −0.62) between the radon concentrations and outside temperature were obtained. The results revealed that high quality air isolation in premises could be an important factor for higher indoor radon levels during summer compared to winter.

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (α_avg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (α_avg. = 0.51).

Traffic‐generated noise accounts for 60–80% of the noise prevailing in towns. With the aim of reducing the impact of noise on humans, measures and methods of fighting noise in towns and residential areas should be developed. In the majority of cases, noise suppression walls (barriers) are one of the most suitable means in tows to reduce the dispersion of noise to residential territories. Acoustic properties of materials to be used for noise walls were investigated and, on the basis of the obtained findings, the most suitable materials with regard to noise reduction were proposed. A noise‐suppression chamber was designed and installed for the experimental investigation into acoustic properties. Separate materials (fibreglass, wood chipboard, gypsum cardboard, foam polystyrene) were used for the experiment by composing various structures of different modifications. With the aim of evaluating the capacity of different materials to suppress noise, a coefficient was used to evaluate noise suppression in a material thickness measuring unit. Efficiency of the noise reduction structures used in the experiment is described by a separate index. Different materials differently suppress the dispersion of noise of various frequencies, whereas the structures of wood chipboards (10 mm) filled with fibreglass or rock wool are the most efficient in all frequency ranges compared with acoustic properties of other structures used during the experiment. Santrauka 60–80 % miestuose vyraujančio triukšmo kelia transportas. Kad triukšmo poveikis žmogui būtų mažesnis, būtina ieškoti priemonių ir būdų triukšmui miestuose ir gyvenvietėse mažinti. Daugeliu atvejų miestuose vienas iš tinkamiausių metodų tam yra triukšmo slopinimo sienelės (barjerai). Tiriant nustatyta triukšmo sienelėms naudotinų medžiagų akustinės savybės bei, atsižvelgiant į gautus rezultatus, siūlomos triukšmo slopinimo požiūriu tinkamiausios medžiagos. Akustinių savybių eksperimentiniams tyrimams buvo sukonstruota ir įrengta triukšmo slopinimo kamera. Tirta skirtingos medžiagos (stiklo vata, medžio drožlių plokštės, gipso kartono plokštės, putų polistirolas) bei iš jų sudarytos konstrukcijos, panaudojant įvairias modifikacijas. Skirtingų medžiagų geba slopinti triukšmą vertinta nustačius koeficientą. Jį taikant gaunamas garso slopinimas medžiagos storio mato vienete. Bandymuose naudojamų konstrukcijų, skirtų triukšmui mažinti, efektyvumas apibūdinamas tam tikru rodikliu. Įvairios medžiagos skirtingai slopina įvairių dažnių garso sklidimą, o medžio drožlių plokštės (10 mm) konstrukcijos su stiklo arba akmens vatos užpildu tam tinka geriausiai. Palyginti su kitomis bandymuose panaudotomis konstrukcijomis efektyviausiai slopinamas beveik visų dažnių diapazonų garsas. Резюме Основным источником шума в городах, составляющим 60–80% общего шума, является транспорт. В целях снижения шумового воздействия на человека необходимо найти пути и средства уменьшения шума в городах и населенных пунктах. Во многих случаях одним из наиболее приемлемых методов уменьшения распространения шума в городах и жилых районах являются звукоизоляционные экраны. Объектом исследования настоящей статьи были акустические свойства материалов, из которых конструируются звукоизоляционные экраны. Полученные результаты показали, какие из проанализированных материалов наиболее применимы для поглощения шума. Для экспериментального исследования акустических свойств материалов была построена шумопоглощающая камера. Исследовались различные виды материалов (стекловата, прессованные древесные плиты, гипсокартон, пенополистирол), а также их конструкции разной модификации. Акустические свойства материалов эффективно поглощать шум характеризуются определенными индикаторами. Наиболее эффективно поглощающими шум всех диапазонов частот по сравнению с другими материалами оказались конструкции, в которых применялись прессованные древесные плиты.

Since society is moving towards sustainable development, interest in secondary use of waste has recently become significant. This paper investigates a process to develop an acoustic material, using two types of waste. Composite acoustic panels were developed using waste tyre textile fibres (WTTF) and paper sludge (PS), and polyvinyl acetate (PVA) were used as a binder. Non-acoustic (bulk density, airflow resistivity) and acoustic (sound absorption coefficient, sound transmission loss) parameters were studied. Composite acoustic panels with different proportions of WTTF/PS/PVA (sixteen samples) were subjected to testing for the sound absorption coefficient according to ISO 10534-2 and sound transmission loss according to ASTM E2611. The density of all samples varied between 155.2 and 709.9 kg/m³, the thickness between 14.4 and 20.5 mm, and the airflow resistivity between 29.5 and 101.5 kPa∙s/m². The results reveal that the proportion of various waste materials in mixtures can improve the acoustic performance of panels. The combination that gives the highest α_avg. with a value of 0.50 was experimentally found to be 70% WTTF mixed with 15% PVA and 15% H₂O. The average sound absorption coefficient with a value of 0.46 was also found to be 25% WTTF mixed with 25% PS and 25% PVA and 25% H₂O. In sound transmission loss, the most effective was 50% PS and the 50% PVA composite, the TL_eq was 28.3 dB, while the composites together with 30% WTTF, 20% PS and 25% PVA, and 25% H₂O showed 18.9 dB loss. The results obtained using WTTF and/or PS wastes are attractive and show great and promising development potential.

This article focuses on the simulation of the impact of ultrafine particles on the rigid partition wall of the multichannel cyclone by applying the discrete element method (DEM). Ultrafine particles with diameters ranging from 0.1 to 10 µm are assumed to be most dangerous pollutants because of their property to easily penetrate the human circulatory system through the respiratory tract. An emphasis is placed on demonstrating the stick-rebound behavior of glass pollutant particles. The numerical experiment simulating the oblique impact load induced by mechanically generated inlet air flow has been numerically conducted. Hertz contact and short-range van der Waals attraction are the main forces describing normal contact, while their tangential counterpart is defined according to Coulomb friction law and by considering normal compression and attraction. Both normal and tangential models are modified to comprise the effect of energy dissipation due to adhesion hysteresis. Simulation results provide a theoretical framework for designing of the cyclone when a device is applied to capture ultrafine pollutant particles.

The development of new sound absorbing materials and the transition to net zero emissions production have become inseparable. This paper investigates a new type of composite sound absorbing material made of waste tyre textile fibre (WTTF) and different binders: polyurethane resin (PU), polyvinyl acetate (PVA), and starch (POS). Non-acoustic and acoustic parameters were studied, and life cycle assessment was performed for the considered composite sound absorbing materials. The airflow resistivity was determined according to the ISO 9053-1 standard, while the sound absorption coefficient was determined according to the ISO 10534-2 standard, and the LCA was performed based on the ISO 14040 and ISO 14044 standards. Composite sound absorbing materials subjected to sound absorption coefficient tests showed results in the range of 0.04 to 0.99 and peaking in the frequency range of 800 to 2000 Hz, while airflow resistivity varied between 17.4 and 83.6 kPa⋅s/m². The combination that gave the highest sound absorption coefficient was experimentally found to be PU composite material. Life cycle assessment results revealed that the lowest potential impact on the environment is obtained when composite materials are produced using starch as a binder and its total potential impact on the environment varied between 0.27 and 0.55 Pt, while the highest potential impact was observed by PU composites (0.33 ÷ 0.64 Pt). The results obtained experimentally and by LCA modelling revealed great attractiveness and promising development of composites using WTTF and different binders’ potential for sound absorbing applications.