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Of special consideration for open spaces are those in the medical industry that includes pharmacies, reception areas, and call centers. These are currently the most difficult applications simply because the expectations are unknown. Personal private information protected by HIPAA will be discussed at a pharmacy, but is it reasonable to expect con- fidential speech privacy in these open spaces? If not, what is an appropriate and reasonable speech privacy expecta- tion? The ASA Committee on Standards, Working Group 44 is currently working on these issues.
Enclosed Rooms
“Come in and close the door, we need to talk.” If you have ever heard or made that statement, then you know that enclosed rooms, such as the one in Figure 1, have completely different speech privacy expectations. At a minimum, the expectation is confidential speech privacy. Listeners outside the room can hear voices but can not understand what is being said inside the room.
In these spaces, voice effort will typically be conversa- tional but can be raised depending on the occupants and situation. In medical examination rooms, caregivers may need to raise their voices for elderly patients with diminished hearing. Conversations may get heated in a manager’s office with the news of a job loss. The founda- tion for meeting these expectations will depend on the appropriate wall and ceiling choices.
The architectural acoustic community has developed several single-number metrics that describe the sound- isolation performance of building components. Examples are the sound transmission class (STC) to evaluate the performance of wall assemblies, and the ceiling atten- uation class (CAC) to evaluate the performance of suspended ceiling systems. The STC and CAC are sin- gle-number ratings calculated in accordance with the
American Society for Testing and Materials (ASTM) clas- sification E413 for sound transmission loss by a partition such as wall (STC) and suspended-ceiling systems (CAC).
As a consequence of having these metrics, good design practice closely matches wall and ceiling performance because the resulting room-to-room sound transmission will be limited by the lowest performing element. A typical enclosed room design will have a wall assembly of gypsum board on each side of 31⁄2-inch-wide studs, with an empty cavity and a mineral-fiber suspended ceiling closely match
the wall sound isolation. This room will typically need a 40 dB background sound to achieve confidential speech privacy. If the occupant desired a lower background noise, then more a robust architectural design is required, such as adding fiberglass insulation in the wall cavity and, again, a closely matching suspended ceiling.
Any sound that travels from room to room other than directly through the wall or ceiling is called acoustic leakage and can significantly compromise the sound isolation and, therefore, speech privacy. Most common examples include door sills and fixtures such as electrical outlets (see Schnitta, 2016). These are easily accounted for with proper placement. For example, it is important to ensure that electrical outlets are never back-to-back in the common wall and that doors are placed at least four feet from the common wall. When the design requires compromised placement, then accommodations such as better doors and door seals may be required.
The focus of this article is commercial spaces. Schnitta (2016) discussed sound isolation for residential applica- tions. In that article, the author points out that residential sound isolation goes beyond speech privacy because the intent is to also minimize, if not eliminate, disturbance from any unwanted sound source.
Classrooms, Boardrooms, and
Patient Rooms
In a classroom, executive board-room, or some govern- ment facilities, confidential speech privacy is not sufficient. The desire is for conversation to not be heard at all.
Executive boardrooms and classrooms have similar needs. Classroom acoustics, as discussed by Brill et al. (2018), have many demands to ensure proper learning. If a student can hear the teacher in the adjacent classroom, that would be a distraction and it would compromise learning. In addition, the teacher’s voice is elevated and the background noise must be low to maintain clear speech intelligibility within the classroom (e.g., Liebold et al., 2019). The combination of high speech privacy expectation, high voice effort, and low background noise requires very robust architectural choices. A higher performing wall is needed, and in most cases, the wall will extend to the structure.
At the same time, we must keep in mind that most mechanical, electrical, plumbing, heating/cooling, and
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