[Reducing noise nuisance in open-plan office rooms by masking unwanted sounds with pyramid-shaped sound columns]. / Zmniejszenie uciazliwosci halasu w biurowych pomieszczeniach open space przez maskowanie dzwieków niepozadanych kolumnami dzwiekowymi w ksztalcie piramid.

BACKGROUND: In order to obtain appropriate, acoustic conditions of working environment in open plan offices, it is necessary to apply quite a large acoustic treatment in these rooms (e.g., to achieve reverberation time 0.2-0.4 s). However, in cases where the background noise levels in rooms are very low (A-weighted sound pressure level <30 dB), then acoustic treatment alone may be insufficient. In such cases, it may be necessary to use a sound system that generate an "artificial" background noise (sound masking system). It is important that the sound masking system must mask the sound in many workplaces. Therefore, sound masking systems contain a large number of sound sources (loudspeakers), evenly distributed throughout the room. Most often, these loudspeakers are placed in a sound-absorbing suspended ceiling. MATERIAL AND METHODS: The article considers the possibility of reducing the number of sound masking sources by using 4-loudspeakers columns. These columns use speakers with much smaller dimensions and less power. The shape of the columns and the arrangement of the loudspeakers in the columns result in a directional radiation pattern that allows for a more even distribution of the masking sound in a room. The article provides the criterion of obtaining a uniform masking sound in the open plan offices. These criteria relate to obtaining appropriate masking sound parameters in the working area, and are based on the criterion value of the distraction distance of the room. RESULTS: The article provides the results of measurement tests of the uniformity of masking sound in the room with the use of the above-mentioned sound masking columns. CONCLUSIONS: It is possible to limit the number of standard masking sound sources in the rooms under consideration using pyramid-shaped sound columns with 4 loudspeakers are used. Med Pr. 2022;73(3):229-40.

[An assessment of acoustic properties of a large-capacity open-plan office room according to a 3-level rating scale - a case study]. / Ocena w skali trzystopniowej wlasciwosci akustycznych biurowego pomieszczenia open space o duzej kubaturze ­ opis przypadku.

BACKGROUND: In open-plan office rooms, one of the main reasons for the nuisance of work is the noise from employees' conversations. In order to limit it, the permissible values of the parameters characterizing the acoustic properties in those rooms on a 2-level scale are defined. MATERIAL AND METHODS: The article introduces a 3-level scale for assessing the acoustic properties (bad, fair, good) of a room based on EN ISO 3382­3:2012 and PN-B-02151-4:2015 - criterion 1. Additionally and alternatively, a new 3-level scale assessment criterion (criterion 2), concerning acoustic separation between groups of workstations, was determined. In order to meet that criterion, it is necessary to take into account the acoustic treatment of the room. A multivariate (7) acoustic treatment studies were performed using computational simulation methods. RESULTS: Requirements, according to PN-B-02151-4:2015, were met after the application of a sound-absorbing suspended ceiling and acoustic screens at workplaces. To meet the requirements of EN ISO 3382­3:2012, it was necessary to additionally use sound-absorbing materials on the walls and acoustic screens separating the naves of the room. To meet the requirements of criterion 2, it was necessary to additionally use acoustic screens separating groups of workstations and acoustic screens in passages. CONCLUSIONS: Appropriate acoustic properties can be obtained in open space offices. Appropriate acoustic properties can be obtained in open-space offices. The requirements according to PN-B-02151-4:2015 can be met with much lower acoustic treatment than the requirements according to EN ISO 3382­3:2012. The use of a 3-level scale for assessing the acoustic properties of a room allows for the differentiation of rooms with regard to their acoustic properties. The introduction of a new assessment method, taking into account the grouping of workplaces in a room, makes it possible to assess the acoustic properties of a room in a more reliable way, by neglecting the impact on the assessment of areas where people are not present. Med Pr. 2021;72(4):375-90.

Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10-40 kHz frequency range.

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 sound-absorbing 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.

[Computational studies of speech intelligibility in open-plan offices]. / Badania obliczeniowe zrozumialosci mowy w pomieszczeniach biurowych open space.

BACKGROUND: Noise in open-plan offices, connected with an unintentional hearing of conversations and related distraction of attention, causes annoyance of employees. The article presents the calculated range of speech intelligibility in a selected open-plan office room. MATERIAL AND METHODS: The speech transmission index (STI) was examined in a real room of 300 m3. The room was equipped with a sound absorbing suspended ceiling, acoustic screens and sound absorbing materials on the walls. Initial tests were conducted in order to verify the assumed computational model from ODEON software, as well as the geometrical and acoustic data describing the room. The verification process consisted of comparing the calculations and measurement results. In the main part of the study, the range of speech intelligibility was calculated for several locations of the speech source, i.e., areas in which the STI > 0.5. RESULTS: The results of the calculations and the results of the measurements of physical quantities, characterizing the acoustic properties of the open-plan office room (including STI), showed good agreement. For speech emission, the ranges of speech intelligibility were determined on several work stations. CONCLUSIONS: The use of calculation methods to simulate the sound field in open-plan office rooms is possible when the calibration of the room model is initially performed. Determination of the speech intelligibility range provides important information about the distance of negative acoustic interactions between work stations. This range can be used to determine the interaction between work stations or to assess various technical solutions to reduce the negative interaction. Med Pr. 2019;70(3):327-42.

[Acoustic conditions in open plan office - Application of technical measures in a typical room]. / Warunki akustyczne w pomieszczeniach biurowych open space ­ zastosowanie srodków technicznych w typowym pomieszczeniu.

BACKGROUND: Noise in open plan offices should not exceed acceptable levels for the hearing protection. Its major negative effects on employees are nuisance and impediment in execution of work. Specific technical solutions should be introduced to provide proper acoustic conditions for work performance. MATERIAL AND METHODS: Acoustic evaluation of a typical open plan office was presented in the article published in "Medycyna Pracy" 5/2016. None of the rooms meets all the criteria, therefore, in this article one of the rooms was chosen to apply different technical solutions to check the possibility of reaching proper acoustic conditions. Acoustic effectiveness of those solutions was verified by means of digital simulation. The model was checked by comparing the results of measurements and calculations before using simulation. RESULTS: The analyzis revealed that open plan offices supplemented with signals for masking speech signals can meet all the required criteria. It is relatively easy to reach proper reverberation time (i.e., sound absorption). It is more difficult to reach proper values of evaluation parameters determined from A-weighted sound pressure level (SPLA) of speech. The most difficult is to provide proper values of evaluation parameters determined from speech transmission index (STI). Finally, it is necessary (besides acoustic treatment) to use devices for speech masking. The study proved that it is technically possible to reach proper acoustic condition. CONCLUSIONS: Main causes of employees complaints in open plan office are inadequate acoustic work conditions. Therefore, it is necessary to apply specific technical solutions - not only sound absorbing suspended ceiling and high acoustic barriers, but also devices for speech masking. Med Pr 2018;69(2):153-165.

[Acoustic conditions in open plan offices - Pilot test results]. / Warunki akustyczne w pomieszczeniach biurowych open space ­ wyniki badan pilotazowych.

BACKGROUND: The main source of noise in open plan office are conversations. Office work standards in such premises are attained by applying specific acoustic adaptation. This article presents the results of pilot tests and acoustic evaluation of open space rooms. MATERIAL AND METHODS: Acoustic properties of 6 open plan office rooms were the subject of the tests. Evaluation parameters, measurement methods and criterial values were adopted according to the following standards: PN-EN ISO 3382- 3:2012, PN-EN ISO 3382-2:2010, PN-B-02151-4:2015-06 and PN-B-02151-3:2015-10. RESULTS: 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 m2 of the room's plan was 0.77-1.58 m2 (minimum permissible value - 1.1 m2; 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.

[Assessment of vocal intensity in lecturers depending on acoustic properties of lecture rooms]. / Poziom natezenia glosu lektorów w zaleznosci od wlasciwosci akustycznych sal wykladowych.

BACKGROUND: Lombard's effect increases the level of vocal intensity in the environment, in which noise occurs. This article presents the results of the author's own study of vocal intensity level and A-weighted sound pressure level of background noise during normal lectures. The aim of the study was to define whether above-mentioned parameters depend on acoustic properties of rooms (classrooms or lecture rooms) and to define how many lectors speak with raised voice. MATERIAL AND METHODS: The study was performed in a group of 50 teachers and lecturers in 10 classrooms with cubature of 160-430 m3 and reverberation time of 0.37-1.3 s (group A consisted of 3 rooms which fulfilled, group B consisted of 3 rooms which almost fulfilled and group C consisted of 4 rooms which did not fulfill criteria based on reverberation time (maximum permissible value is 0.6-0.8 s according to PN-B-02151-4:2015). Criteria of raising voice were based on vocal intensity level (maximum value: 65 dB according to EN ISO 9921:2003). The values of above-mentioned parameters were determined from modes of A--weighted sound pressure level distributions during lectures. RESULTS: Great differentiation of vocal intensity level between lectors was found. In classrooms of group A lectors were not using raised voice, in group B--21%, and in group C--60% of lectors were using raised voice. CONCLUSIONS: It was observed that acoustic properties of classrooms (defined by reverberation time) exert their effect on lecturer's vocal intensity level (i.e., raising voice), which may contribute to the increased risk of vocal tract illnesses. The occurrence of Lombard's effect in groups of teachers and lecturers, conducting lectures in rooms, was evidenced.

[Effects of acaoustic adaptation of classrooms on the quality of verbal communication]. / Wyniki badan wplywu adaptacji akustycznych sal lekcyjnych na jakosc komunikacji werbalnej.

BACKGROUND: Voice organ disorders among teachers are caused by excessive voice strain. One of the measures to reduce this strain is to decrease background noise when teaching. Increasing the acoustic absorption of the room is a technical measure for achieving this aim. The absorption level also improves speech intelligibility rated by the following parameters: room reverberation time and speech transmission index (STI). This article presents the effects of acoustic adaptation of classrooms on the quality of verbal communication, aimed at getting the speech intelligibility at the good or excellent level. MATERIAL AND METHODS: The article lists the criteria for evaluating classrooms in terms of the quality of verbal communication. The parameters were defined, using the measurement methods according to PN-EN ISO 3382-2:2010 and PN-EN 60268-16:2011. Acoustic adaptations were completed in two classrooms. RESULTS: After completing acoustic adaptations the reverberation time for the frequency of 1 kHz was reduced: in room no. 1 from 1.45 s to 0.44 s and in room no. 2 from 1.03 s to 0.37 s (maximum 0.65 s). At the same time, the speech transmission index increased: in room no. 1 from 0.55 (satisfactory speech intelligibility) to 0.75 (speech intelligibility close to excellent); in room no. 2 from 0.63 (good speech intelligibility) to 0.80 (excellent speech intelligibility). Therefore, it can be stated that prior to completing acoustic adaptations room no. 1 did not comply and room no. 2 barely complied with the criterion (speech transmission index of 0.62). After completing acoustic adaptations both rooms meet the requirements.

[Vocal intensity in lecturers: results of measurements conducted during lecture sessions]. / Poziom natezenia glosu wykladowców--wyniki badan przeprowadzonych podczas wykladów.

BACKGROUND: Occupational voice users (inter alia: lecturers) speak with different levels of vocal intensity. Speakers adjust this intensity knowingly (e.g. to underline the importance of fragments of the speech) or unknowingly. The unknown adjustment of voice intensity occurs e.g. in the presence of high acoustic background noise (so-called Lombard effect), but it also results from many other factors: hearing loss, construction of the vocal tract, habits and others. The aim of the article is to confirm the thesis that in similar conditions of acoustic properties of the room different lecturers speak with different levels of vocal intensity. MATERIALS AND METHODS: The study was conducted in a group of 10 lecturers in the same conference room. A-weighted sound pressure level determined at 1 m from the lecturer's mouth was adopted as a parameter defining the intensity of the lecturer's voice. The levels of all lecturers' voice intensity were compared and evaluated according to the criteria defined in EN ISO 9921. RESULTS: Nine in ten lecturers were speaking with normal voice intensity (60-65 dB) and only one full-time university lecturer was speaking with raised voice (66-71 dB). CONCLUSIONS: It was found that in the room of the same acoustic conditions the lecturers spoke with different intensities of voice. Some lecturers occasionally, and one all the time spoke with the voice intensity specified by PN-EN ISO 9921 as a raised voice. The results of the preliminary study warrant further studies in a larger group of teachers.