The article presents results of our own research regarding acoustic properties of 110 classrooms in five typical primary schools in Warsaw. The target of the research was to assess the classrooms using established criteria. These criteria include the reverberation time and the speech transmission index. The research has shown a large diversity of acoustic properties of classrooms within each of the schools and between the schools, resulting from the classroom equipment and the school building construction. In addition, the assessment has indicated that classrooms in schools researched do not meet the established acoustic criteria (reverberation time and speech transmission index). Because the classroom equipment is different for younger forms (integrated teaching) and for older forms (subject teaching), the results have been analyzed separately for rooms for younger forms (0-III) and for rooms for older forms (IV-VI). Synthetic results prove the advisability of such division. Correlation analysis has been conducted for the speech transmission index STI and reverberation time T mf , as well as for the speech transmission index STI and the suggested reverberation time T wf defined in a similar manner as T mf , but in a wider frequency range. The correlation between the speech transmission index STI and T wf is higher than that between the STI index and T mf . The reverberation time T wf can therefore be used for a more precise assessment of acoustic properties of interiors with regard to verbal communication than T mf . In addition, the paper presents estimated analysis results of the influence of selected classroom equipment (carpets) on its acoustic properties.
The assessment of teachers' exposure to noise in primary schools was carried out on the basis of: questionnaire studies (covering 187 teachers in 3 schools), noise measurements at the teachers' workplaces, measurements of the school rooms acoustic properties (reverberation time and speech transmission index STI in 72 classrooms), analysis of statistical data regarding hazards and occupational diseases in the education sector. The studies have shown that noise is the main factor of annoyance in the school environment. Over 50% of questioned teachers consider noise as annoying and near 40% as very annoying or unbearable. A-weighted equivalent continuous sound pressure levels measured in classrooms, teacher rooms and common rooms are in the range of 58-80 dB and they exceed 55 dB (criteria of noise annoyance). The most frequently reported subjective feelings and complaints (over 90%) are: growth of psychical and emotional tension, irritation, difficulties in concentrating, hoarseness, cough. Noise in schools is also a harmful factor. High A-weighted equivalent continuous sound pressure levels ranging from 80 to 85 dB, measured in corridors during pauses and in sports halls, can cause the risk of hearing damage among PE teachers and persons oversensitive to noise. The latter concerns both teachers and pupils. High background noise levels (55-65 dB) force teachers to raise their voice. It can lead to the development of an occupational disease -chronic voice disorders due to excessive vocal effort lasting for at least 15 years. In the education sector 785 new cases of this disease were reported only in 2008. Poor acoustics in classrooms (reverberation time ranging from 0.8 to 1.7 s, STI < 0.6 in 50% of classrooms) have an adverse influence on speech reception and make the teaching and learning processes difficult.
Sound absorption coefficient is a commonly used parameter to characterize the acoustic properties of sound absorbing materials. It is defined within the frequency range of 100-5 000 Hz. In the industrial conditions, many appliances radiating acoustic energy of the frequency range of above 5000 Hz are used and at the same time it is known that a noise within the frequency range of 5 000-50 000 Hz can have a harmful effect on people,hence there is a need to define the coefficient in this frequency range. The article presents a proposal for a method of measurement of the sound absorption coefficient of materials in the frequency range from 5 000 Hz to 50 000 Hz. This method is a modification of the reverberation method with the use of interrupted noise.
W artykule przedstawiono wyniki badania obliczeniowego, wpływu zastosowania dźwięków maskujących na zrozumiałość mowy na stanowiskach pracy w typowym pomieszczeniu biurowym open space. Jako dźwięki maskujące uwzględniono dźwięki o czterech charakterach widm częstotliwości i o poziomach dźwięku A z zakresu 25-45 dB. Kryteria oceny akustycznej biurowych pomieszczeń open space przyjęto wg PN-EN ISO 3382-3:2012 i PN-B-02151-4:2015 (właściwości akustyczne pomieszczenia) oraz PN-B-02151-2:2018 (poziom tła akustycznego, w tym i dźwięku maskującego). Wykazano, że jest możliwe uzyskanie odpowiednich warunków środowiska pracy (w tym własności akustycznych pomieszczenia) przy poziomie dźwięku A dźwięku maskującego z zakresu 31-37 dB (w zależności od rozpatrywanego jednego z czterech typów charakteru widma dźwięku maskującego).
The reverberation time was 0.33-0.55 s (maximum permissible value in offices -0.6 s; the criterion was met), sound absorption coefficient in relation to 1 m 2 of the room's plan was 0.77-1.58 m 2 (minimum permissible value -1.1 m 2 ; 2 out of 6 rooms met the criterion), distraction distance was 8.5-14 m (maximum permissible value -5 m; none of the rooms met the criterion), A-weighted sound pressure level of speech at a distance of 4 m was 43.8-54.7 dB (maximum permissible value -48 dB; 2 out of 6 rooms met the criterion), spatial decay rate of the speech was 1.8-6.3 dB (minimum permissible value -7 dB; none of the rooms met the criterion). Conclusions: Standard acoustic treatment, containing sound absorbing suspended ceiling, sound absorbing materials on the walls, carpet flooring and sound absorbing workplace barriers, is not sufficient. These rooms require specific advanced acoustic solutions. Med Pr 2016;67(5):653-662
Two test stands for determining sound insulation in the frequency range above 5 kHz were made. One consisted of two horizontally adjacent reverberation rooms and a special source of high frequency sounds and ultrasounds. The other test stand consisted of a miniaturized test chamber and a special source of ultrasounds. The paper presents results of the preliminary measurements of sound insulation properties of different barriers in the frequency range above 5 kHz.
Wstęp: Hałas w pomieszczeniach biurowych open space, powodując niezamierzony odbiór rozmów i związaną z tym dekocentrację, jest szczególnie uciążliwy dla pracowników. W artykule określono metodą obliczeniową zasięg zrozumiałości mowy w wybranym pomieszczeniu biurowym open space. Materiał i metody: Badano zrozumiałość mowy określoną wskaźnikiem transmisji mowy (speech transmission index − STI) w pomieszczeniu rzeczywistym o objętości 300 m 3 . Zainstalowano w nim dźwiękochłonny sufit podwieszany, ekrany oraz materiały dźwiękochłonne na ścianach. W badaniach wstępnych zweryfikowano przyjęty model obliczeniowy (w programie ODEON) oraz dane geometryczno-akustyczne opisujące pomieszczenie. Weryfikacja polegała na porównaniu wyników pomiarów i wyników obliczeń. W badaniach głównych obliczono zasięg zrozumiałości mowy dla kilku wariantów położenia źródła mowy, tj. obszarów, w których STI > 0,5. Wyniki: Uzyskano dużą zgodność wyników obliczeń i pomiarów wielkości fizycznych charakteryzujących właściwości akustyczne pomieszczenia biurowego open space (m.in. STI). Na kilku stanowiskach pracy określono zasięgi zrozumiałości mowy dla jej emisji. Wnioski: Stosowanie metod obliczeniowych do symulacji pola akustycznego w pomieszczeniach biurowych open space jest możliwe po wykonaniu kalibracji zastosowanego modelu geometryczno-akustycznego i danych opisujących pomieszczenie. Określenie zasięgu zrozumiałości mowy daje istotną informację o zasięgu negatywnego akustyczne wzajemnego oddziaływania stanowisk pracy. Zasięg ten może być wykorzystany przy określeniu wzajemnego oddziaływania stanowisk pracy lub oceny różnych rozwiązań technicznych, które mają na celu zmniejszenie tego oddziaływania.
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