If conversations can be inadvertently overheard, occupants can also become self-conscious about their own level of privacy. In some contexts, it can create a sense of unease, which in turn impacts the ability to freely communicate. For instance, if a patient can hear what is happening in the adjacent examination room at a medical clinic, he or she might be less inclined to disclose information to the nurse or doctor, out of fear of being overheard.
The degree of acoustic privacy afforded by the built environment can even impact an organization’s brand image. People want to be in control of personal information when meeting with a financial or legal advisor, for example, and a positive acoustic experience can reinforce confidence in a firm. This level of protection is also indispensable for staff to effectively negotiate the terms of various agreements.
In some countries, the protection of verbal communication within particular types of facilities is actually mandated by law. The Health Insurance Portability and Accountability Act (HIPAA) introduced by the U.S. Department of Health and Human Services in 1996 is a good example. It requires healthcare entities to take “reasonable safeguards” to ensure there is speech privacy during both in-person and telephone conversations with patients and between employees.
Acoustic privacy is also vital to employees’ overall satisfaction with their workplace. A worldwide, decade-long survey of more than 65,000 people run by the Center for the Built Environment (CBE) at University of California, Berkeley, found lack of speech privacy is the top complaint in offices.2 Participants expressed irritation at being able to overhear in-person and telephone communications, as well as concern for their own level of privacy.
What about the open plan?
The topic of workplace satisfaction also emphasizes the need to consider those occupying spaces other than closed rooms. Though some may dismiss the importance of acoustic privacy when designing an open plan, studies show it has a significant impact on productivity.
For instance, research conducted by Finland’s Institute of Occupational Health shows unwilling listeners demonstrate a five to 10 per cent decline in performance when undertaking tasks such as reading, writing, and other forms of creative work. Simply hearing someone is speaking can disturb concentration, but this problem is greatly magnified when one can clearly understand what is being said because, if a conversation can be followed, it is much harder to ignore it.
Though an organization might not consider privacy a goal within an open plan, it is impossible to justify increasing disruptions. Taking the steps required to lower speech intelligibility within this type of space increases occupants’ output and reduces error rates.
Assessing speech intelligibility
The subject of speech intelligibility cannot be discussed without getting into the concept of degrees because every word of a conversation does not need to be understood for privacy to be violated. Due to the redundancies and patterns in speech, building occupants can follow much of what is said even if only half of it is overhear—particularly if they have previously been part of a similar conversation. Further, private details can be exposed even when a small part of the discussion is overheard.
Further, it is difficult to subjectively assess degrees of speech intelligibility. For example, a listener would have a hard time indicating with any precision whether they can understand 40, 55, or 70 per cent of what someone else is saying.
Fortunately, there are ways to measure and quantify the degree of privacy afforded by the built environment. The Articulation Index (AI) remains the most widely used method. It was developed at Bell Labs in 1921 by Harvey Fletcher as he sought to quantify speech comprehension over telephone lines. During the 1950s, those that were involved in the speech privacy sciences adopted his invention as a measure of exactly the opposite: how much one could not understand.
