{"id":128155,"date":"2021-07-09T15:34:21","date_gmt":"2021-07-09T19:34:21","guid":{"rendered":"https:\/\/www.constructionspecifier.com\/?p=128155"},"modified":"2023-12-06T17:32:30","modified_gmt":"2023-12-06T22:32:30","slug":"in-pursuit-of-acoustical-equity","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/in-pursuit-of-acoustical-equity\/","title":{"rendered":"In pursuit of acoustical equity: Controlling temporal, spectral, and spatial properties of sound"},"content":{"rendered":"
\"Photo<\/a>
Photo \u00a9 Vincent Lions Photography<\/span><\/em><\/figcaption><\/figure>\n

by Viken Koukounian, PhD, P.Eng., and Niklas Moeller<\/strong><\/p>\n

Given the intense focus on health and safety as well as the changes in work\/life balance precipitated by the COVID-19 outbreak, it is not surprising the pandemic has accelerated the healthy-building movement and the \u2018people-first\u2019 mindset spearheaded by standards such as WELL and Fitwel. There is burgeoning consensus that buildings need to be designed with deep commitment to the well-being of their occupants.<\/p>\n

Effective acoustics are key to healthy buildings. After all, noise is known to provoke physiological stress responses that can negatively impact occupants. The World Health Organization (WHO) describes it as an \u201cunderestimated threat\u201d contributing to stress, high blood pressure, cardiovascular disease, dementia, and diabetes. Therefore, WELL and Fitwel take acoustics into consideration; however, it remains a poorly understood indoor environmental quality (IEQ) parameter, and the lowest rated (referenced from \u2018Green buildings and health,\u2019 Global Environmental Health and Sustainability, vol. 2, 2015, by G. J. Allen, P. MacNaughton, J. G. Cendeno Laurent, S. S. Flanigan, E. S. Eitland and J. D. Spengler).<\/p>\n

Returning to the workplace<\/strong><\/p>\n

Low scores have added significance in today\u2019s climate. Many employees found a silver lining in the ways in which stay-at-home orders enriched their family lives, even as the scope of their work and social lives contracted. As companies start to bring\u2014or attempt to draw\u2014them back to the office, occupant satisfaction is more important than ever. Organizations need to implement strategies to not only keep staff safe and healthy, but also happy and productive enough within their working environment that they actually want to come in.<\/p>\n

Amongst the architecture and design community, there is growing conviction these goals must be achieved through concern with \u2018equity\u2019\u2014and applied to \u2018real-world\u2019 needs such as acoustical privacy, rather than amenities like pool tables, private chefs, and other perks; in other words, it is more a matter of how employees are treated than what they are being treated to (for more information, read Talitha Liu and Lexi Tsien\u2019s article in \u2018The Office as We Knew It No Longer Exists,\u2019 Azure<\/em>, September 2020).<\/p>\n

\"Figure<\/a>
Figure 1:<\/strong> The person (green) in Room 1 speaks at a \u2018Casual\u2019 level, while the person (red) in Room 2 uses a \u2018Normal\u2019 level (i.e.<\/em> per Pearsons). Despite the latter\u2019s elevated vocal effort, they enjoy speech privacy due to the higher and consistent background sound level within Room 1. On the other hand, the person in Room 1 does not have speech privacy due to the lower and variable nature of the background sound in Room 2; however, they believe they have privacy, by virtue of the fact they cannot hear the person in Room 2.<\/span>
Images courtesy KR Moeller Associates Ltd.<\/span><\/em><\/figcaption><\/figure>\n

Firms such as Gensler point out that although employees are enjoying benefits (e.g.<\/em> more time with family and less spent commuting) while working from home, many are also struggling with less-than-ideal conditions (e.g.<\/em> poor internet connectivity, shared workspace with children and other family members, noisy neighbors and neighborhoods) that negatively impact their engagement and productivity. Whether an organization wants their office to be occupied fulltime post-pandemic or to serve as a critical part of a hybrid working model, it has the potential to act as a \u2018great equalizer<\/a>\u2019\u2014a shared facility that is specifically designed to support employees\u2019 work and overall well-being.<\/p>\n

According to the 2020 Gensler Work from Home Survey, 88 percent of employees would like to return to the workplace in some capacity. One of the primary reasons the 2300-plus participants cite is the need for a quiet, distraction-free environment\u2014a desire echoed by the 32,000-plus people polled during studies Steelcase<\/a> conducted across 10 countries. It is clear acoustics matter and, therefore, are vital to ensuring employees not only enjoy equal access to the facility itself, but also to the IEQ parameters that are needed to work comfortably and effectively.<\/p>\n

The question is, what is \u2018acoustical equity\u2019 and how does one achieve it?<\/p>\n

The sound that actually exists<\/strong><\/p>\n

En route to answering these questions, one must first consider the traditional approach to acoustics, which relies on \u2018categorization\u2019 and \u2018acceptable-level\u2019 schemes prevalent throughout building standards and codes. The former specifies sound-rating values (e.g.<\/em> sound transmission class [STC], noise isolation class [NIC], impact isolation class [IIC], ceiling attenuation class [CAC]) for the boundaries of a room or building envelope, while the latter uses noise-rating values (e.g.<\/em> noise criteria [NC], noise rating [NR], room criteria [RC]) to set maximum limits for noise, such as those generated by building systems, services, and utilities. However, neither offer insight into the \u2018actual acoustics\u2019 (i.e.<\/em> the sound actually present) within a space or occupant experience of it.<\/p>\n

To improve results\u2014a goal that one can, with a broad brushstroke, call \u2018better acoustics\u2019\u2014and fulfill the objective of designing with occupants in mind, one must turn their attention to the sound actually present in a space and look at it through the lens of both architectural acoustics (i.e.<\/em> the study of sound and its behavior in and due to a space) and psychoacoustics (i.e.<\/em> the study of the psychological and physiological effects of sound and its perception). Indeed, one cannot be separated from the other, as psychoacoustical evaluation of a space considers the outcome of the combined performance of all acoustical features.<\/p>\n

\"Figure<\/a>
Figure 2:<\/strong> The person in Room 1 briefly has speech privacy\u2014and the person in Room 2 a corresponding reprieve from disruption\u2014when the background noise produced by the HVAC system temporarily reaches the level required for privacy, highlighting the need to establish minimum background sound levels in addition to maximum noise thresholds.<\/span><\/figcaption><\/figure>\n

Acoustical privacy is key<\/strong><\/p>\n

The reactions of building occupants are captured using psychoacoustic metrics, some of which are subjective (e.g.<\/em> surveys evaluating comfort, distraction, perceived productivity) and others that are objective (e.g.<\/em> intelligibility, audibility).<\/p>\n

Research shows one\u2019s overall acoustical satisfaction is strongly correlated with acoustical privacy, a concept with clear ties to the workplace, but one that is also relevant to other environments. For example, surveys of multi-unit residences demonstrate links between acoustical privacy and annoyance, fatigue, and sleeping problems (e.g.<\/em> due to noise from traffic and neighbors) (consult B. Rasmussen and O. Ekholm\u2019s paper \u2018Is noise annoyance from neighbours in multi-storey housing associated with fatigue and sleeping problems?\u2019 in Proceedings of the 23rd<\/sup> International Congress on Acoustics [ICA], Aachen, Germany, 2019). In other words, although people tend to equate acoustical privacy with speech privacy, the former is not limited to the intrusion of speech content; it also considers the audibility of unintelligible speech and other types of noise.<\/p>\n

That said, it is challenging to use acoustical privacy as a starting point for a conversation about acoustical equity. The science around acoustical privacy is not sufficiently nuanced; it is not yet addressed by a standardized metric or even a proposed methodology.<\/p>\n

Speech privacy, on the other hand, is both well-defined and measurable (e.g.<\/em> using articulation index or speech privacy class). Therefore, it is a psychoacoustic metric that can be used in both theoretical (i.e.<\/em> to illustrate the concept of acoustical equity) and practical ways (i.e.<\/em> to set expectations during design and estimate occupants\u2019 subjective impression of the built space). In this case, evaluation of acoustical privacy is effectively a review of the signal-to-noise ratio; it considers an intruding \u2018signal\u2019 (speech) and its level relative to the background \u2018noise\u2019 (or, rather, sound) in the receiving space (for more information about the differences between \u2018noise\u2019 and \u2018sound,\u2019 read Viken Koukounian and Niklas Moeller\u2019s article \u2018Rethinking Acoustics: Understanding silence and quiet in the built environment<\/a>\u2019 in the May 2021 issue of The Construction Specifier<\/em>).<\/p>\n

By way of example, see the rooms\u2014and occupants\u2014shown in Figure 1:<\/p>\n