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Background: Hearing loss caused by excessive exposure to noise is one of the most common health risks for employees. One solution for noise reduction is the use of hearing protectors, which is a very effective method for protecting hearing from the workplace noise. In order to obtain better attenuation efficiency, custom moulded earplugs can be equipped with a suitable acoustic filter. The effectiveness of the hearing protectors' attenuation is based on real measurement of hearing thresholds for normal hearing people with and without hearing protectors. However, this is a time consuming process, and the obtained values are characterised by quite large inter-individual variability. The optimal solution is to measure the attenuation characteristics based on the objective method (without the presence of the subject), the results of which will be in accordance with the results of subjective tests. Therefore, the main purpose of the research in this work was to measure the attenuation characteristics of the self-designed custom moulded earplugs with and without acoustic filters through the use of subjective and objective methods, and to compare the results in terms of the research methods. Methods: Measurements of the acoustic attenuation obtained by custom moulded earplugs with designed F1, F2, and F3 acoustic filters (internal diameters dF1 = 1:25 mm, dF2 = 0:85 mm, and dF3 = 0:45 mm), as well as full insert earplugs (without any acoustic filters) were carried out using two methods: objective and subjective. The objective measurements were carried out in an anechoic chamber. The artificial head (High-frequency Head and Torso Simulator Brüel & Kjær Type 5128) was located at a distance of 3 m, directly opposite the loudspeaker. The test signal in the measurements was pink noise - in the frequency range up to 12.5 kHz and the level 85, 90, and 95 dB. The hearing protectors with and without acoustic filters were mounted in the Head and Torso Simulator which was connected with Pulse System Brüel & Kjær. Five normal hearing subjects participated in the subjective measurements. A pink noise signal was used for one-third octave bands: 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. The attenuation value was defined as the difference (in dB) between the hearing threshold of the test signal with a hearing protector and the hearing threshold determined without a hearing protector. Results: The results of the objective method proved that in addition to the significant impact of frequency on the attenuation values, the type of filter used in custom moulded earplugs also had a significant effect. In addition, the results of the objective method showed that in the whole frequency range the highest attenuation values are shown by the full earplugs, achieving slightly above 45 dB for frequency of 8 kHz. The attenuation values obtained from subjective measurements also confirmed that both the frequency and type of filter significantly affect the attenuation values of the tested hearing protectors. Conclusions: The results of this study did not confirm the hypothesis that the measurement method had no significant effect on the attenuation characteristics of self-designed custom moulded earplugs with different types of acoustic filters. The largest differences in attenuation values between the type of measurement methods occur for the low frequency band (250 Hz) and for higher frequencies (4000 Hz mainly). The change of the internal diameter of the F1 filter from 1.25 mm to 0.85 mm (F2 filter) did not significantly affect the attenuation characteristics. [ABSTRACT FROM AUTHOR]

A noise sensitive zone is characterized by a noise limit. An industrial zonewith a cluster of companies is planned in vicinity of this noise sensitive zone. In this study, the noise emission limits for each company, expressed in terms of the sound power level, are calculated. The calculations are performed for favorable conditions of sound generation and propagation. It is shown how the noise emission limits depend on the dimensions of the industrial zone and the distance to the noise sensitive zone. The exact results require numerical integration. To simplify the calculations, the idea of the curved rectangular is used. [ABSTRACT FROM AUTHOR]

Usually, the time-term average sound level, L, is not directly measured but calculated from the measured sound exposure levels. Variance of L1,…, Ln quantifies the uncertainty of noise measurements. In any case, a decrease in the variance means an increase in the quality of measurements. This paper shows how to decrease the variance of L1,…, Ln. [ABSTRACT FROM AUTHOR]

The article offers information on the life and works of the late professor Bogusław Marian Rosa. Born on 4 May 1925 in Warsaw, Poland, Rosa dedicated over 60 years to scholarly work and active research into the south Baltic coast, history of the Baltic Sea and the Quaternary topographic profile. He was a man of remarkably broad research interests which embraced glacial geomorphology, littoral dynamics, and paleogeography of the Quaternary.

Abstract: The composition and concentration of lignin phenols (used as biomarkers of organic matter quality gradients) and granulometric and mineral composition were studied, in order to document land cover variations, in a dated (using the 210Pb method, validated with 137Cs distribution) sediment core from a small lake (Pusty Staw) in the coastal Baltic Sea area. Substantial gradients were found in the granulometric composition. These were attributed to varying erosion caused by deforestation and afforestation of the catchment area. Extrapolation of the dating to deep core layers showed that the deforestation layer originated from 1730 AD, close to a period of deforestation found in historical records. The core dating was validated by matching a peak in the 137Cs profile with the 1986 Chernobyl accident. Changes in the use of the catchment area caused substantial shifts in organic matter composition and quality, as suggested by the gradients of syringyl (S), cinnamyl (C), and vanillic (V) phenols derived from CuO/alkaline oxidation of lignin. The lignin component of the sedimentary organic matter originated primarily from angiosperm woody material (S/V=0.8; C/V=0.4). A new lignin parameter, called delta (Δ), indicating the burden of lignin-derived organic matter deposited in sediments with mineral matter, shows changes between the uppermost and middle zones of the core. An increased ratio of vanillic acid (Ad) to vanillone (Al) in the uppermost sediment layers was noticed and attributed to the inflow of degraded organic matter washed out from the catchment area soil. Principal component and cluster analysis indicated the lignin load and quality as the main factors distinguishing the organic material in the core sections. Both the lignin load and quality gradients were in agreement with the lithology of the core, showing the steepest gradients at the boundaries of core sections deposited prior to/after the deforestation/afforestation events. [Copyright &y& Elsevier]