The overlooked importance of office acoustics

The move from traditional cellular offices to open-plan arrangements has perhaps been the facilities management story of recent times. While many have railed against the dehumanising, industrialised rows of desks, there is a growing awareness that it is possible to get more out of people by enabling an environment more conducive to their work.

But noise remains among the main complaints, according to research by employee experience think tank Leesman, and the traditional acoustic tools for open-plan office design are very blunt. We urgently need a different way of understanding acoustic conditions to enable new designs for offices.

Bear in mind that the acoustic environment of different workplaces can be very varied depending on the activities undertaken there, and the culture of the organisation. There is no standard approach but the acoustic environment has to be appropriate to the needs of the occupants if it is to work effectively.

Since ISO 3382-3 was published in 2012, the approach to acoustic design has been to evaluate the indicators in that standard and compare them with guidance values. These indicators move beyond the simplicity of measuring reverberation time or how echoey it is, to consider the rate decay of sound with distance, that is how far you need to go until it gets quieter, the speech level at 4m – how noisy it is when someone talks – and the distance beyond which speech starts to become less distracting.

But these indicators are about the acoustic response of the office space to noise when it is unoccupied, rather than how it sounds when it is occupied. There are no British standards that describe how to design open-plan offices acoustically for different types of use, and although the British Council for Offices Guide to Specification: Best practice for offices of 2019 talks broadly about some of the issues, it reverts to descriptions and criteria for a building's performance when unoccupied, rather than for the experience of occupants.

Designing for acoustic satisfaction in open-plan offices is about much more than just the characteristics of the empty room. It is first about considering the activities for which it is used, such as working individually, collaborating with colleagues at the desk, or talking on the telephone.

Intolerance of workplace noise can in this case be understood as annoyance that interferes with the ability to concentrate and work effectively. Annoyance is closely related to the level of control we have over our environment. A German psycho-acoustic study indicates that only about 30-40 per cent of the annoyance due to noise can be attributed to the acoustic response of the room. Moderators of such annoyance include the ability to control the noise, the attitude towards the noise-maker, the predictability of the noise event, the activity profile of the employee, the organisational and business structure workload, other environmental factors such as illumination or thermal comfort, and individual noise sensitivity.

Productivity is most closely related to the ability to concentrate and focus on a task. Noise – unwanted sound, and particularly unwanted speech – interferes with the ability to concentrate by what is termed the irrelevant speech effect. Unwanted speech interferes with our own internal conversation, which causes distraction. Many different researchers have suggested that providing a protected space for focused work can be the single most important aspect of the acoustic design.

This method starts by considering the acoustic needs of occupants for different activities, such as working individually, collaborating and being on the phone, and how other tasks can affect them. It considers the occupied environment from the outset and determines the acoustic separation that is required to protect one type of activity from another in an open space, which is characterised by the new indicator DAS. The Apex method can also take account of how much control people have over noise in determining the acoustic protection required. Where people have more control, for example, if they can choose which desk to work at, our case studies show that they tend to be more tolerant of adverse acoustic conditions than those who have less control, such as when desks are assigned.

This new method is not prescriptive, the acoustic requirements can be achieved by blocking sound propagation using barriers, screens, furniture, booths or pods, by separating spaces at a distance, or introducing systems that generate a masking sound. Implementing appropriate features is part of the design development process. The method offers clear and consistent information about noise that is intuitive to understand and easy to communicate with the design team and client. Potential conflicts between different types of use are highlighted, and responses identified in acoustic terms that can be implemented in different ways in the design and spatial constraints.

The Apex method is gaining widespread recognition winning two awards from the Association of Noise Consultants and another for soundscape from the Noise Abatement Society. The method is also referred to in the forthcoming ISO 22955 as a way to determine acoustic requirements between areas with different use types.

Creating the optimum acoustic environment for a workplace is as much an art as it is a science because it also relies on the behaviour of the occupants. As designers we don't control how people behave: we work with the staff and management to understand how work is carried out, what conditions are necessary, and how conflicts may have arisen in the past.

Spatial planning is one of the most important acoustic aspects of the design, but it is frequently carried out by interior designers without acoustic expertise or assistance. Until now there haven't been robust acoustic tools for this; the Apex method enables the acoustic consultant to illustrate to other members of the design team where acoustic conflicts may occur and how they can be designed out. We can demonstrate the effects that different finishes have on the acoustic response of the space and interpret this in terms of potential acoustic environment for the occupants.

A recent Dutch study shows that when faced with a noise problem people commonly adopt avoidance strategies such as taking work home. But the strategies rated as most effective are those that involve addressing or discussing the issue. A new workplace is a new opportunity – or imperative – for change. Managing that change towards new ways of working that include an acoustic etiquette can enable significant improvement in peoples experience at work.

This is an exciting and fast-changing area for acoustic design. With office accommodation increasingly seen as a service rather than an asset, which needs to meet the functional, operational and well-being needs of the occupants, rather than exclusively focusing on the building fabric criteria, creating suitable acoustic conditions for people and their activities is vital.

Jack Harvie-Clark is founder of Apex Acoustics jack.harvie-clark@apexacoustics.co.uk