Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in th
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RESEARCH ARTICLE
Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10–40 kHz frequency range Witold Mikulski 1 Received: 28 August 2019 / Accepted: 4 October 2020 # The Author(s) 2020
Abstract Purpose The purpose of the research is to work out a method for determining the sound insulation of acoustic enclosures for industrial sources emitting noise in the frequency range of 10–40 kHz and apply the method to measure the sound insulation of acoustic enclosures build of different materials. Methods The method is developed by appropriate adaptation of techniques applicable currently for sound frequencies of up to 10 kHz. The sound insulation of example enclosures is determined with the use of this newly developed method. Results The research results indicate that enclosures (made of polycarbonate, plexiglass, sheet aluminium, sheet steel, plywood, and composite materials) enable reducing the sound pressure level in the environment for the frequency of 10 kHz by 19–25 dB with the reduction increasing to 40–48 dB for the frequency of 40 Hz. The sound insulation of acoustic enclosures with a soundabsorbing material inside reaches about 38 dB for the frequency of 10 kHz and about 63 dB for the frequency of 40 kHz. Conclusion Some pieces of equipment installed in the work environment are sources of noise emitted in the 10–40 kHz frequency range with the intensity which can be high enough to be harmful to humans. The most effective technical reduction of the associated risks are acoustic enclosures for such noise sources. The sound pressure level reduction obtained after provision of an enclosure depends on its design (shape, size, material, and thickness of walls) and the noise source frequency spectrum. Realistically available noise reduction values may exceed 60 dB. Keywords Sound insulation . Acoustic enclosures . Soundproof enclosure . Ultrasound . Sound power level
Introduction In their everyday life and work environment, humans are exposed to a plurality of harmful and uncomfortable factors. The noise is defined as sounds (acoustic vibrations) showing undesirable and/or harmful effect on humans or making it difficult to carry out specific activities. Such sounds reach humans as airborne stimuli. The fundamental parameter characterising quantitatively the intensity of sonic phenomena (including noise) in the frequency range 20–20,000 Hz is the Aweighted sound pressure level. Any noise characterised with values of that parameter exceeding 80 dB [1–7] can be the cause of permanent damage of hearing in a human being. In * Witold Mikulski [email protected] 1
Central Institute For Labour Protection — National Research Institute, 16 Czerniakowska Str., Warsaw, Poland
Poland, the A-weighted sound pressure level of 85 dB is adopted as the so-called maximum admissible intensity (MAI) applicable in the context of the hearing protection [2, 3]. Any noise with the A-weighted sound pressure level falling in the range 55–75 dB can be detrimental to or prevent t
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