Field study for the evaluation of the acoustic quality of open-plan offices

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.

The effect of sound masking on employees' acoustic comfort and performance in open-plan offices in Canada

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.

Biophilic Sound Masking Systems: Promoting Acoustical Comfort in Workspaces

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 building's environment on people's 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.

Spatial uniformity tolerances for sound masking systems in open-plan offices

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.

Acoustical Conformance with FGI for Tenant Improvements in Outpatient, Medical Office or Clinic Facility Sound Isolation/Privacy Design

Acoustical privacy and noise control design and implementation guidance is needed, regarding Facility Guidelines Institute (FGI) criteria for outpatient medical facilty tenant improvements (TI). TI in existing commercial buildings or medical office buildings may not have capital budgets or expected facility/lease life that hospitals enjoy. Full conformance to FGI criteria and guidelines may be limited; by economic feasibility and by constructability. Design professionals can use "good practice" space planning, demising assembly selection, and electronic sound masking to achieve appropriate acoustical privacy within reasonable capital expense budgets. Consider FGI criteria for demising partition, ceiling, door and window selections plus infrastructure equipment and material selections that can provide cost-effective lightweight, common construction standards. The objectives are to protect the privacy of patient information and provide quiet spaces, free of transient disturbance for clear speech communications. Continuous ambient sound increases speech privacy including speech transmitted from enclosed quiet spaces. Criteria for acoustics, speech privacy,continuous noise and masking exists in FGI. Temporal level changes (on/off, transients) and tonality (spectrum smoothness or balance) should be considered in basis-of-design (BoD). This paper will present design guidelines for selecting demising assemblies and supplemental sound masking for outpatient clinical spaces in commercial or medical office buildings.

Creating a sound-designed sound masking signal for open-plan offices that is both pleasant and has a positive impact on cognitive performance.

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.

114 Tackling Noise Pollution in Hospitals: A Pre-Feasibility Study

This study aimed to better understand appropriate interventions aimed at reducing hospital ward noise and the subsequent impact this would have on inpatient experience. Service users consistently reported that noise pollution was the most detrimental factor in their recovery in hospital, principally due to its effects on sleep. Methods To aid usability and data collection the Richards- Campbell Sleep Questionnaire (RCSQ) was adapted into an electronic format with a sliding Likert scale using QuestionPro Software3. Qualitative patient interviews, the RCSQ and ward decibel measurements were recorded on Henry and Anne wards at St. Thomas’ Hospital, London. 20 patients were interviewed (12F, 8 M), with 3 being ultimately discounted due to severe cognitive impairment. Results were collated and will be presented as part of a pre-feasibility evaluation of the tools to measure patient sleep and experience of ward noise. Results: The mean of the responses from the 17 patients interviewed were calculated and graphically displayed. Of interest, 87.5% found the questionnaire straightforward to understand, but only 18.75% found it easy to complete (due to technological unfamiliarity). Conclusion and discussion Patients reported a consistently reported a less than optimal night’s sleep on the ward, with light sleep and increased time to fall asleep being key factors. Although visits were restricted to the “quietest” times on the ward, noise measurements consistently exceeded WHO recommendations of 40 dB. Subsequently excessive night-time noise created by other patients as well as staff was cited as the principal causes of poor sleep, with ward lighting being another cause. Results from this study have provided the justification for sound-masking technology to be trialled on inpatient wards, with the view of decreasing unpleasant ward noise and improving patient rest and recovery.