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The acoustics of open-plan offices

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The benefits of having an open-plan office layout is the ability to obtain thermal and lighting comfort with less energy use, a goal emphasized by green design. The office space is considered as a single thermal zone with a single air conditioning treatment while daylight is capable to penetrate throughout the entire space.

 

The acoustic drawbacks of open plan office are:

• Without room barriers, it becomes difficult to avoid unwanted noise from equipment such as copy and printer machines.

• Speech intelligibility improvement has the drawback in speech privacy quality and work distraction

• Optimal distance between the workstations is critical.

Acoustical problems that occur within open-plan offices are related to communication comfort between co-workers. Problems include distortion of speech intelligibility due to interference by unwanted sound, lack of speech privacy and interruption during the communication by other co-workers.

Speech scenarios & acoustical problem in the open-plan office

Scenario 1, the speaker requires high speech privacy with the listener in workstation 1 and avoids the spread of confidential conversation to listener in workstation 2.

Scenario 2, the listener in workstation 2 can be distracted by the conversation between speaker and listener in workstation 1.

Scenario 3, the listener in workstation 2 often requires the ability to clearly understand the speech content from the speaker in workstation 1.

The improvement is suggested by open plan office modifications through simulation approach.

• Modification by workstation models: The workstation model is modified by the design of the table on the workstation, the constraint of this model is the height that used for all model is the same.

• Modification by workstations layout: This modification is applied by changing the arrangement of the workstations position. In this simulation, the numbers of workstations are the same for each arrangement.

• Modification by workstation partition heights: In this simulation, several workstations height are used to improved the acoustic parameters. The table model on the workstation is the same.

(Simulation is based on ray tracing method using commercial software (CATT.9.0), and the parameters are calculated based on ISO 3328-3:2012 for open plan office.)

The overall simulation result shows that each model has unique characteristics of open plan office, for example in straight line path, the model IV has the highest STI to the nearest workstation but at the same time has the shortest privacy distance in general. This means this kind of model is good for type open plan that group between adjacent tables based on the work.

 

 

There is a unique difference of speech privacy conditions among 3 types of layout. For example, Layout 3 has STI values the highest compare to other layouts. But on the contrary, it has the shorter privacy and distraction distances among them. It means for short distance from source the communication condition is good but for longer distance it is poor. This kind of type is good for open plan office that utilize group job.

The overall simulation results show that the higher the workstation partition, the better the communication comfort. But the result also shows that the improvement is not significant. This result may occur due to the diffraction phenomena by partition which has not been treated well in simulation.

 

 

 

Excerpt from the white paper “Characterizing the acoustics of ‘green’ open-plan offices,” by Joko Sarwono & Sentagi Sesotya Utami that appeared in the Proceedings of ICSV20, Bangkok-Thailand, July 2013.

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