Biophilic Sound Masking Systems: Promoting Acoustical Comfort in Workspaces
Time: 8:40 am
Author: Ethan Salter
Abstract ID: 1813
Promoting speech privacy and acoustical comfort in office buildings has always been an important consideration for designers, owners, and occupants. Acoustical comfort has many degrees, including reduction of stress, enhancing focus, and reducing distractions. It can also create a more pleasurable and relaxing environment. Concurrently, the sustainable and green design movements have evolved the language of design and building to include a more holistic understanding of occupant comfort. This includes the materials and systems that occupants interface with and use. Additionally, interior environmental quality considerations, including noise, are incorporated into green building rating systems such as WELL, LEED, CHPS, and others. However, it is not merely about providing a slightly better or more efficient system, but also understanding on a deeper level the effects of a buildings environment on peoples health. One aspect of this is the concept of biophilia, where designers look to natural systems and materials for inspiration. The interior acoustical environment is a significant part of that. Electronic sound masking systems have been used in office environments for decades, and their efficacy, when appropriately designed and installed, has been proven repeatedly. What has been changing in recent years is the concept of biophilic sound masking systems, which do not merely broadcast broadband noise (AKA pink noise or "white" noise) in a space. These systems can broadcast natural sounds such as running water, animals, wind, etc. that are not only pleasing and soothing, but also effective in sound masking. This paper will describe biophilia in general how it relates to the interior noise environment, and related design considerations. In addition, the paper includes a case study of an office building project that employed a sound masking system with biophilic capabilities.
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Creating a sound-designed masking signal for open-plan offices: pleasant in sound and with positive impact on cognitive performance.
Time: 7:40 am
Author: Benjamin Mueller
Abstract ID: 2713
In open-plan offices, sound masking is often used to lower speech intelligibility and raise cognitive performance of the employees by reducing the irrelevant speech effect. Classic sound masking methods use speakers built into the ceiling of the office to increase the overall background noise level in the office and reduce speech intelligibility. However, the emergence of activity based offices is increasing the need for personalized sound masking methods that are no longer used globally in the office, but can be controlled by each employee individually depending on their activity and, for example, played back through headphones during activities that require particularly intense concentration. The playback of a classical sound-masking noise (e.g. a simple pink noise filtered by -5 dB per octave) via headphones is effective, but not pleasant. For this reason, a new sound-designed masking signal was developed in the present study, which consists of slowly fluctuating binaural harmonic components, as well as atmospheric sounds like water sounds and masking noise. A listening test with a cognitive task and a survey after each test condition showed that the developed signal had a similar positive effect on cognitive performance as a classical masking noise, but was rated as significantly more pleasant.
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Effect of visual elements on Indoor soundscape perception in open-plan office
Time: 6:00 am
Author: Beta Bayu Santika
Abstract ID: 2988
This study examined the effect of changes in visual elements on spatial comfort and work productivity in the aspect of indoor soundscape perception in the open-plan office (OPO) sound environment. Various OPO visual stimuli were simulated using computer software (Unity 3D engine) to change the visual environment by varying variables such as worker density, window ratio, green ratio, and ceiling height. An interactive virtual reality environment was implemented to perform a specific task while experiencing the audio-visual stimuli combining the general OPO noise stimulus and the simulated OPO visual stimulus. Subjective evaluation was performed on a total of 30 subjects to evaluate indoor soundscape quality and work performance for each stimulus. Based on the results of this study, a pleasant OPO design guideline was proposed. Keywords: Open-plan office, indoor soundscape, interactive VR test, spatial comfort
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Just noticeable difference of Lp,A,S,4m specified ISO 3382-3
Time: 8:20 pm
Author: HARAM LEE
Abstract ID: 2990
In this study, the general sound environment characteristics of open-plan office (OPO) were investigated, and just noticeable difference (JND) of sound pressure level of speech at a distance of 4 m (Lp,A,S,4m) suggested in ISO 3382-3 was suggested. First, in order to understand the sound environment characteristics of OPO, one minute sound sources recorded in 8 offices were collected and physical and psychological acoustic characteristics were analyzed. A total of 30 office workers were subject to subjective evaluation on 8 sound sources, and they were asked to respond to questionnaires related to annoyance, work satisfaction, and speech privacy. Next, to investigate the JND, two computer simulation models identical to those of the actual OPO were implemented, and sound sources each having six different Lp,A,S,4m values were generated through the change of the sound absorption coefficient of the interior finish. The JND of Lp,A,S,4m was presented by performing paired comparison for the same subjects. It is expected that the JND of Lp,A,S,4m proposed in this study can be used for the sound environment rating of OPO.
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Spatial uniformity tolerances for sound masking systems in open-plan offices
Time: 9:00 am
Author: Roderick Mackenzie
Abstract ID: 3199
Electronic sound masking systems raise the ambient sound level in offices to a controlled minimum sound level in order to increase speech privacy and reduce distractions. Sound masking systems are calibrated to provide the most uniform sound field achievable, as a spatially non-uniform masking sound field could result in occupant perception and uneven speech privacy conditions. Tolerances for acceptable spatial uniformity vary between specifiers, and may be based on different evaluation methods using only a few discrete measurement points to represent an entire office space. However, the actual uniformity of a masking sound field across an office, and the parameters influencing it, has not been widely investigated. Thus, this study aims to investigate the masking sound uniformity in a typical open-plan office space using fine-grid measurements conforming to measurement method of ASTM E1573-18. Percentages of measured locations where the sound pressure levels were within specified tolerances (with increments of 0.5 dB) were calculated using the measured 1/3 octave band levels. The research also utilized geometric acoustical simulations to investigate how physical office parameters (number of loudspeakers, partition heights, ceiling absorption, and diffusion characteristics) affect the sound field uniformity of the sound masking system.
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The effect of sound masking on employees acoustic comfort and performance in open-plan offices in Canada
Time: 8:40 pm
Author: Roderick Mackenzie
Abstract ID: 3215
Sound masking systems are commonly used in open-plan offices to generate a controlled minimum level of background sound, in order to decrease the signal-to-noise ratio of intrusive speech and blend out transient office noise. However, a question in the acoustical design of offices is whether the self-generated noise of occupants may alone be sufficient to provide the background sound level conditions necessary to achieve similar levels of speech privacy and acoustic comfort as sound masking systems. This study examines the relationship between occupant-perceived speech privacy and acoustic comfort under three different acoustic scenarios (no masking, controlled 42 dBA, and 47 dBA masking sound levels). The study was conducted pre-COVID-19 in two separate open-plan offices located in Quebec, Canada that at the time were close to full occupancy. Employees completed subjective questionnaires before and after each change in conditions, focusing on how the sound environment impacted their comfort and work performance during the study. Statistical results show that the occupants were significantly more satisfied during the two sound masking conditions in comparison to the no-masking condition, where only the occupant-generated and exterior/mechanical system noise was present as the background sound. Implications for open-plan offices with lower occupancy conditions post-COVID-19 are discussed.
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Field study for the evaluation of the acoustic quality of open-plan offices
Time: 8:00 am
Author: Patrick Chevret
Abstract ID: 2168
Even if the global health crisis is currently changing the work organisation in offices in the service industry, the problem of noise in open plan offices remains a major challenge with regard to occupational health and well-being. Since 2012, the French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS) has been carrying out acoustic surveys in French open-plan offices by measuring both some usual indicators of empty offices (Tr, D2S, Lp4m, rc, Lp) and also the ambient noise levels in activity. In addition, GABO questionnaires have been proposed to employees to assess their perception of the noise environment. So far, 50 open spaces were evaluated, with more or less data collected depending on the situation encountered. Approximately 1,400 employees have already answered the questionnaire. All of the sites visited cover the entire set of activities described by the ISO 22955 standard. An analysis of the links between the acoustic parameters and the perception of employees was carried out. This analysis provides additional information to the studies on the choice of acoustic descriptors and on the use of sound masking systems that aim to control background noise to reduce noise disturbance due to intelligible conversations.
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Impact of Partition types on Architecture design studios acoustical environment
Time: 8:20 am
Author: Hany Hossam Eldien
Abstract ID: 3328
Working in Architecture design studios environment requires various activities. Interaction, communication and meetings could affect the speech intelligibility and the speech privacy conditions. Students Areas with a more silent environment are needed with a minimized level of distraction from surrounding activities, while teamwork and discussion areas with a high level of interaction need a good speech intelligibility. One of the more important elements which can improve the open spaces acoustical conditions is the partitions between workstations.The main purpose of this work is to evaluate the acoustical performance of four partitions types in open plan offices; 1.10m two sides partition height, 1,50m front side partitions, 1,50m one side partitions and 1.50 two sides partitions. This Study was conducted in the College of Architecture, Imam Abdulrhman Bin Faisal University, KSA. Based on ISO 3382-3, Speech Transmission Index, STI in the nearest workstation, Distraction distance rD, privacy distance rP, A-weighted background noise level L,A,B and A-weighted SPL of speech at 4 metres L,A,S,4m have been measured. It was found that the best results can be obtained by 1.50m front side and 1.50m two sides partitions.
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