where the employee workspaces are not separated by definitive structural features such as walls. Compared to traditional cellular offices, open plan offices provide opportunities to adapt to various configurations within the given space thereby allowing the means to accommodate more people in the area( Schlittmeier & Liebl 2015). In a study comparing occupants in open plan offices and cellular offices, common sources of dissatisfaction in the former was air quality and thermal comfort( Pejtersen et al. 2006). Mucous membrane symptoms, headaches and fatigue were 2-3 times more prevalent in occupants of open plan offices, with almost 8 times more occupants having concentration difficulties. Post occupancy surveys are an important means of understanding the problems faced by occupants of indoor environments( C. Huizenga et. al 2006). Such information is a vital tool in optimising the existing buildings to achieve better occupant comfort and satisfaction. Secondly, it can provide information for future design and construction of buildings and indoor environments. Since occupant satisfaction has a positive relation to their perceived productivity( Leaman et al. 2007), optimising the indoor environment would have economic benefits for the employers.
Occupants expressed satisfaction of noise levels at an approximate level of 45dB( Huang et al. 2012). Performance of cognitive tasks is reduced at the normal sound levels of 51dB( LAeq) prevalent in offices while there was significantly less distraction at lower levels of 39 dB( LAeq). Although the ideal scenario for acoustic efficiency would be to create individual rooms for each employee, limited space makes this economically and functionally impractical. In such situations, efficient planning and development of the acoustic quality of spaces should be considered so as to create a more acoustically viable environment( Jensen & Arens 2005). Spatial organisation is an effective means of reducing background sound within the work environment( Jahncke et al. 2013; Schlittmeier and Liebl 2015; Jensen & Arens 2005). Designating separate zones for employees with concentration intensive tasks can ensure less distraction due to ambient speech. Employees with speech intensive jobs( such as sales personnel) could be spatially segregated from employees who require greater silence and concentration in their tasks. This could enable greater efficiency and job satisfaction. Another spatial tactic would be to designate quiet zones or‘ think tanks’ to conduct concentrated work and communication rooms to conduct phone calls. Encouraging an office culture of acoustic etiquette, or having a timeframe for silence during the day, are some measures that can be adopted by the employers to achieve an acoustic friendly environment for all( Schlittmeier and Liebl 2015).
Although optimised spatial arrangement and office culture are initial measures in improving workplace acoustics, it cannot in itself block ambient speech and noise. Thus, it is imperative to employ methods that will reduce the disturbance caused by ambient noise. To achieve this, the sound signal from the emitter would have to be modified such that it has minimal impact on the cognitive function as well as the subjective understanding of the recipients. Laboratory and field findings demonstrate that is possible to create a STI below 0.5( LAeq), which is an approximate threshold level beyond which task performance gets affected by sound disturbance, within a 2.5 – 5 m radius of the workstation( Jahncke et al. 2013). Using sound absorbent interior finishes( flooring, wall coverings, ceiling panels, soft furnishing, etc.) will help absorb the sound energy. Partition screens can be covered on both sides to moderately create a sound barrier between workstations. Although these measures reduce the distraction impact of background speech on the listener, often the speech is still distantly intelligible. By using sound masking techniques, the ambient speech can be superimposed with a‘ masking’ sound signal so as to considerably reduce the disturbance effect of the background speech( Schlittmeier and Liebl 2015; Huang et al. 2012; Jahncke et al. 2013; Jensen & Arens 2005). Proposed masking levels for open plan offices are in the range of 40 and 45dB( LAeq).
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