acoustic walls
Introduction
The best office is a functional office fit for purpose. This goal can be easily compromised through a lack of acoustic design input. Without proper acoustical advice, trends such as warehouse conversions, exposed soffits, glazed partitions and concrete surfaces, can be a dangerous design option that can lead to an unsuccessful project.
As mentioned in Acoustic Design for Education, we know that the most successful projects will be ergonomically designed to consist of both positive aesthetic and acoustical qualities. The result of ineffective or non-existent collaboration will lead to issues for end-users such as inefficient and costly redesign practices. Architects and designers must consider beyond the aesthetics, and acoustic consultants must consider more than the auditory environment.
Acoustics Considerations for Office Fitouts
Office acoustics should support the aesthetic design and ultimately lead to greater productivity, concentration, job satisfaction and well-being. Acoustic comfort is paramount in achieving effective workplaces.
A study of over 100,000 workers shows that only 30% of office occupants are satisfied with the noise levels in their workplace [1]. Worksafe QLD states that excessive noise levels can: interfere with concentration and thought processes, cause fatigue and aggression, lead to heart disease and reduce immune response [2].
Office acoustics noise also causes distraction, which leads to negative performance in the workplace and makes us less productive [3, 4]. Furthermore, after distraction, it takes an average of 23 minutes and 15 seconds to get back to the task, leading to wasted time [5]. This implies that in a frequently noisy environment you may never be back to task!
Psychologists have also stated that distractions degrade the overall quality of people's work [6]. Other Psychologists have shown that noise has an impact on ‘free recall’ or memory functions [7]. Furthermore, the Australasian Faculty of Occupational Medicine states that noise has the potential to give rise to direct compensable absence and indirect workplace absenteeism [8]. Another study indicated that noise is linked to stress in the workplace and can even lead to musculoskeletal disorder through noise exposed workers being less likely to correct their posture [9].
The Association of Australasian Acoustical Consultants (AAAC) states that “if adequate intelligibility and acoustic comfort were provided, concentration would be easier, and participants would be less frustrated and more productive” [10].
Open Plan Offices
Each workplace area will have its own set of acoustical requirements. In particular, open plan office solutions are perhaps the most challenging and will require the greatest attention to detail from your acoustical consultant.
The benefits of an open plan office are said to include greater collaboration, reduction in hierarchy, higher creativity, reduced construction costs and flexibility. It has also been published that those who work in open plan offices tend to have higher levels of physical activity at work and lower levels of stress outside the office [11].
Open plan offices have been adopted by the likes of Google and Facebook and exist in many workplaces in Australia. However, open plan office acoustics are more susceptible to the issue of mismanaged noise [12, 13]. One study that provided evidence from 42,764 workers collected in 303 office buildings indicated that distraction by noise and loss of privacy were identified as the major causes of workspace dissatisfaction in open-plan office layouts [14].
Another study by Oxford Economics states that open plan offices come with serious drawbacks like noise and distraction [15]. It was further noted in this research that the most important aspect of a work environment stated by employees was the ability to focus and work without interruptions [15].
Office Acoustics Standards
According to AS/NZS 2107:2016, different room functions will dictate the appropriate level of internal noise and reverberation time in order to increase acoustic comfort [16]. It is stated that in open plan offices “Reverberation time should be minimised for noise control” [16]. The AAAC also states that open plan spaces result in compromised acoustics, with sound absorption on the office acoustic ceiling becoming particularly critical in determining sound isolation [9].
Essentially, this means that shorter reverberation times with acoustically treated surfaces are ideal. Hard surfaces like plasterboard, concrete and solid floors should be avoided, as these will create longer reverberation times.
Studies also show that controlling reverberation is key to minimising the negative effects of an open plan office. One particular study investigated the effect of two different room acoustics on: employees’ perception of disturbances, cognitive stress and professional efficiency [17]. It was shown that the better acoustically treated environment had a more positive effect on employees.
For boardrooms and conference rooms, controlled reverberation times are important, with some reflective surfaces to carry the voice for speech intelligibility. Longer reverberation times cause syllables to be prolonged and in turn will reduce the quality of the acoustic environment.
According to Worksafe Queensland, generally low background noise is important; however, too low of a noise level can interfere with activities or concentration and causes similar stress and health effects as high level noise [2]. The AAAC also states that spaces should have a suitable amount of ambient noise [9].
Solutions with Decorative Acoustic Panels
In most cases, good office acoustics can be achieved by designing to the recommended reverberation times and noise levels set out in AS/NZS 2107:2016. This means utilising decorative office acoustic panels in the design stages in collaboration with your acoustic consultant.
Acoustic absorption should be evenly distributed throughout the space, although in many cases you will find that the first place utilised is the ceiling – especially in open plan offices where ceiling absorption is particularly important. It is also important to understand the way that reverberation time is calculated assumes that absorption is evenly distributed throughout the space. Office spaces should also be free from negative acoustic phenomena such as flutter echoes and focussing effects. Acoustic wall panels are especially effective in these instances.
The diffusive properties of room finishes and contents can also be strategized to influence the quality of room acoustics. For example, a bookcase on a rear wall can be used to scatter sound within a space and break up long delayed echoes. This is especially important in rooms with a rear wall distance greater than 8.5 metres.
Reflection is also important, with short delays under 50 milliseconds being beneficial to speech intelligibility, especially in boardroom and conference rooms. It is when strong reflections after 50 milliseconds occur that a degradation of speech intelligibility will happen.
Resonant absorbers such as fire-rated timber acoustic panels can be especially effective as they can be used to provide a healthy amount of absorption across the frequency spectrum. This means that they do not promote excessive high frequency absorption, which can be especially important for rooms with lots of carpet installed. Timber also has great biophilic benefits that can help boost productivity through connecting humans to nature!
Wrap Up
It can be very easy to miss the mark with office designs and end up with an unsuccessful project. Comprehensive analysis and collaboration should be conducted with your acoustic consultant and acoustic panel manufacturer early on in any office project.
You can find qualified acoustic consultants here; https://aaac.org.au/member-firms
Acoustic Engineer
About the Author
Michael Phillips is an acoustic engineer who specialises in engineering acoustic treatments for both aesthetic and acoustic design requirements.
Creator of bespoke treatments including; diffusion and absorption, wall and ceiling systems, curved beams and panels.
For more information on acoustic solutions, email Michael at [email protected] or phone 61+ 02 6333 8014.
References
[1] Leesman Review Issue 17, 2015
[2] Worksafe Queensland, Effects of Excessive Noise, How your body reacts, accessed 2020
[3] Dr Nigel Oseland – Workplace Strategist & Change Manager
Video; Introduction to Psychoacoustics – the study of personality and reaction to noise. https://www.ecophon.com/en/about-ecophon/Contact/Request-information/office-whitepaper/
[4] Simon Banbury, Dianne C. Berry, First published: 13 April 2011, British Journal of Psychology, Volume 89, Issue 3 ‘Disruption of office‐related tasks by speech and office noise’
[5] Mark, Gloria & Gudith, Daniela & Klocke, Ulrich. (2008). The cost of interrupted work: More speed and stress. Conference on Human Factors in Computing Systems - Proceedings. 107-110. 10.1145/1357054.1357072.
[6] Foroughi, C. K., Werner, N. E., Nelson, E. T., & Boehm-Davis, D. A. (2014). Do interruptions affect quality of work?. Human Factors: The Journal of the Human Factors and Ergonomics Society, 56(7), 1262-1271. doi: 10.1177/0018720814531786
[7] Beaman, Philip. (1998). Irrelevant Sound Disrupts Order Information in Free Recall as in Serial Recall. The Quarterly Journal of Experimental Psychology A. 51. 615-636. 10.1080/027249898391558.
[8] Australasian Faculty of Occupational Medicine, ‘Workplace Attendance and Absenteeism’, THE ROYAL AUSTRALASIAN COLLEGE OF PHYSICIANS, December 1999
[9] J Appl Psychol. 2000 Oct;85(5):779-83. Stress and open-office noise. Evans GW1, Johnson D. Department of Design and Environmental Analysis, Cornell University, Ithaca, New York 14853-4401, USA
[10] Association of Australian Acoustical Consultants Guideline for Commercial Building Acoustics, Version 1.0, June 2017, Association of Australian Acoustical Consultants (AAAC), Available at: www.aaac.org.au
[11] Casey M Lindberg1, Karthik Srinivasan2, Brian Gilligan3, Javad Razjouyan4,5, Hyoki Lee4, Bijan Najafi4, Kelli J Canada6, Matthias R Mehl7, Faiz Currim2, Sudha Ram2, Melissa M Lunden8, Judith H Heerwagen3, Kevin Kampschroer3, Esther M Sternberg1
‘Effects of office workstation type on physical activity and stress’
[12] Banbury, S. P., & Berry, D. C. (2005). Office noise and employee concentration: Identifying causes of disruption and potential improvements. Ergonomics
[13] Smith-Jackson, T. L., & Klein, K. W. (2009). Open-plan offices: Task performance and mental workload. Journal of Environmental Psychology
[14] Jungsoo Kim, Richard de Dear ‘Workspace satisfaction: The privacy-communication trade-off in open-plan offices’ Faculty of Architecture, Design and Planning, The University of Sydney, NSW 2013, Australia
[15] Oxford Economics 2016 ‘When the Walls come down – How smart companies are rewriting the rules of the open workplace’ https://www.oxfordeconomics.com/when-the-walls-come-down
[16] Australia/New Zealand Standard, 2016, AS/NZS2107:2016, Acoustics - Recommended design sound levels and reverberation times for building interiors, Australia/New Zealand Standard.
[17] Aram Seddigh, Erik Berntson, Fredrik Jo€nsson, Christina Bodin Danielson, Hugo Westerlund The effect of noise absorption variation in open-plan offices: A field study with a cross-over design’, The Stress Research Institute, Stockholm University, SE-106 91, Stockholm, Sweden
The Department of Psychology, Stockholm University, SE-106 91, Stockholm, Sweden
Stockholm School of Economics Institute for Research, Stockholm School of Economics, SE-113 83, Stockholm, Sweden