Abstract
The publication presents a comparison of the sound absorption test results of a perforated wall cassette filled with mineral wool for various degree of cement dust pollution. Cement dust should be understood here as dust created during the production of cement and during the milling and dispatch of finished products. If the partitions in production plants are made of sound-absorbing cassettes or additional sound-absorbing elements made of perforated cassettes are applied, we must know how dust can change sound-absorbing properties of the cassettes. Thus, one has to consider whether the use of sound-absorbing perforated cassettes is appropriate if sound-absorbing parameters change over time due to dust. To determine the impact of dust-covered perforation on sound-absorbing parameters, tests were performed for four variants having different level of pollution. The tests involved ‘clean’ and then dust-covered cassettes, each time increasing the amount of cement dust on the perforations. Sound absorption parameters of the cassettes were tested in the reverberation chamber for individual variants. Test results indicate the loss of sound absorption of the cassettes only when they are heavily polluted. Then the reduction of the single-number sound absorption index αw is 50%. Using computer simulation, we analyzed how the change of sound-absorbing parameters of the cassettes would influence the change of noise reduction in the production hall. The results of the analysis demonstrate a very effective reduction of noise level of 14 dB by the application of clean cassettes. The reduction value for the dirtiest cassettes was 6 dB.
Highlights
One of the most important roles in terms of room acoustics is played by the phenomenon of reverberation
The decrease of the sound-absorbing parameters of sound-absorbing cassettes observed in the tests due to contamination with cement dust will in practice lower their effectiveness in reducing noise
The measurements carried out for four variants of dust pollution degree of the cassettes demonstrate a close relationship between the amount of dust deposited on the cassettes and sound absorption coefficient
Summary
One of the most important roles in terms of room acoustics is played by the phenomenon of reverberation. Reverberation is measured by reverberation time, which is the main criterion in the assessment of the acoustic quality of rooms [1]. The reverberation time in rooms depends on acoustic absorption, which, in turn, depends mainly on the sound absorption of materials used for their construction. For this reason, perforated cassettes with mineral wool filling are often used as building envelopes [6]. One of the reasons to decrease reverberation time in rooms is the need to reduce reverberation noise. This is important in public utility buildings and in industrial facilities [7]. According to Oishi and Schacht [9], according to the WHO report, it was estimated that 10%
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