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Private Offices, Not So Private

Ever since the tragedy of 9/11, senior management from both private and public sectors have been in a state of heightened concern over increasing the security of information that is communicated - both written and oral.

This concern covers a wide range of subjects: spanning from human resource discussions, to next quarter’s financial performance, to top-secret meetings with military defense contractors.

Unfortunately, today’s typical private offices do not provide adequate speech privacy. In fact, the typical private office provides far less than the minimum required level of confidential speech privacy. Most offices allow occupants located outside these private offices to easily overhear and understand sensitive conversations that occur inside.

This conclusion comes from the results of a yearlong collaborative study by Dynasound Inc., Armstrong World Industries, and SMED International. The project was coordinated with the aid of the IFMA Healthcare Council.

This study highlights the key points and summarizes the effectiveness of the acoustical correction, including the addition of soundmasking solutions. Recommendation included will enable new offices under construction, as well as most existing private offices, to be upgraded in a cost effective manner to achieve confidential speech privacy with minimal construction activity.

Today, far more sophisticated applications of soundmasking are available to protect top-secret information from either inadvertent, deliberate, or electronic eavesdropping (i.e. laser beams and parabolic microphones aimed at executive conference room windows). High security solutions include specialized masking products for many areas in offices.

The study involved 40 major healthcare participants and was conducted with facility managers. It included representation of 30 million square-feet of facilities. The results were as follows:
• 73% of facility managers interviewed reported they had issues related to acoustical problems. Most of the problems involved patients in private offices who could hear and understand doctors’ conversations with other patients in adjoining offices.
• 75% rated these acoustical issues as medium to high priority.
• 45% reported that previous acoustical corrections were not effective
• None of these facilities in the study had soundmasking
• These survey results in healthcare facilities were very comparable to corporate private office environments, which also did not provide confidential speech privacy.
The reasons for determining why most private offices lacked confidential speech privacy were as follows:
• Traditional interior design selects ceiling systems, walls, and doors that are laboratory tested and rated individually for acoustical performance.
• Components are not laboratory tested according to specific field installation. They do not factor in job-site construction conditions, such as utility penetrations and construction tolerances, resulting in sound leaks and reduced speech privacy
• Most conventional acoustical ceilings are laboratory tested without light fixtures, air diffusers, return air grilles, sprinkler heads, etc. Each of these penetrations, which occur in “as built” installation, cause sound leaks that significantly lower the published Ceiling Attenuation Class (CAC) ratings of ceiling sound transmission.
• Other “as built” construction of walls and floors typically contain sound leaks that reduce the laboratory rated performance. Air leaks around light fixtures, non-baffled return air ceiling grilles, back-to-back electrical boxes in walls, defective wall joints, gasketless partition interface at ceiling, inefficient doors and seals, gaps between bottom of doors and finished floors, poor ceiling tiles, and substandard ceiling grid installations are some examples.

To address this problem, the collaboration’s private office acoustical tests (performed at Armstrong’s laboratory) included the ceiling penetrations listed above. The results paralleled “as built” performance of private offices. The same is also true with the SMED Life Space modular floor-to-ceiling wall system and its respective penetrations. There were two “as built” fully equipped offices constructed inside the acoustical test chamber in order to obtain “real world” performance data on sound transmission effectiveness.

In most modern offices, the use of Variable Air Volume (VAV) systems reduce the air movement through ductwork, reducing the buildings background sound level. As a result, air volume varies widely depending on the thermal load. The sound level varies accordingly, and at many times during the year, the building background sound can be very low. Consequently, modern office buildings can be at times very quiet, allowing confidential conversations to be overheard. This is the case in both open and closed office plans.

Lastly, in many private offices, soundmasking systems are mistakenly overlooked in the interior design stage. As will be seen in the test results, the use of a properly designed and installed soundmasking system is a critical element in increasing speech privacy levels. This prevents individuals from overhearing and understanding conversations from inside private offices.
The American Society of Testing and Materials (ASTM) defines the Privacy Index (PI) as the rating of the degree of speech intelligibility.

Confidential speech privacy is achieved when only muffled words can be overheard from room to room. A rating of 95% to 100% of the PI provides “confidential” privacy. At this level, no one outside the closed room can understand speech intelligibility. This is the goal of well-designed private offices. Any rating less than 95% will sacrifice confidentiality, allowing conversations to be understood outside the private office.

The collaboration’s site tests, s well as laboratory analysis of speech privacy performance, showed that the typical closed plan private office currently has a PI of 75%. This represents a total loss of the confidentiality of all conversations.

Since 95% PI is the start of confidential speech privacy, the 75% rating of common private offices is far below acceptable performance. By comparison, a well-designed open plan office environment should achieve a minimum 80% PI. This level provides 50% sentence intelligibility, yet most employees will not be distracted at this level unless they concentrate on a specific conversation. Obviously at 75% PI, private offices are simply conduits for the loss of security of sensitive or confidential information. This is a high security risk and is unacceptable.

The three key components to achieve confidential speech privacy were found to be:
• Use ceiling high fixed drywall or the preferable choice of modular partition systems with a minimum of 35 Sound Transmission Class (STC) performance. Use of appropriate floor partition tracks that either gasket or are designed to “grip” the carpet and retain the 35 STC performance at the floor line. Termination of partition systems at the ceiling line, using similar closures and gaskets between the top track and the ceiling system. Insuring that doors and door gaskets create a good sound seal.
• Use lay-in suspended ceiling systems that span a facility continuously across the entire plan. Whenever possible upgrade the ceiling system sound absorption performance to .70 Noise Reduction Coefficient (NRC) while maintaining a minimum 35 CAC. Several commercial ceiling tiles (high performance mineral fiber) provide these performance ratings. The higher sound absorption will absorb and reduce the speech intelligibility within the room before it infiltrates into adjacent offices.
It is critical to provide a baffle (attenuator) over the top of all open return air grilles. These devices will prevent most of the sound from passing from these private offices directly into the plenum. Sound attenuators are typically made from either mineral fiber ceiling tiles or prefabricated metal closures. When properly installed, the baffles will allow the return air to pass through them while reducing transmitted speech intelligibility.
• Provide a properly designed, installed, and tuned (adjusted) soundmasking system for all private office areas. masking will uniformly raise the buildings background sound level so that occupants in private offices, or adjacent open plan areas, will not be able to distinguish or understand speech intelligibility.

The collaboration found that because of the various sound leaks that occur with “as built” interior components, it would be virtually impossible to provide confidential speech privacy with partitions stopping at the ceiling line without the use of a well designed, installed and tuned soundmasking system.

Even if partitions passed through the ceiling system, they would have to extend to the deck above and be perfectly sealed in order to achieve confidential speech privacy. In addition, all return air grilles would have to be ducted or attenuated to avoid the loss of speed privacy as previously described.

The combination of sealed partitions to the deck and the use of ducted return air systems would substantially increase the overall cost of the building. It would also eliminate interior space flexibility.

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