Acoustics of Corporate Offices
By Stalin Vera, INCE Bd. Cert., LEED Green Associate
To attract talent and support a flexible hybrid environment, new office spaces are being fit out in new and existing buildings throughout the country. As virtual web-conferences are the new norm for communication and collaboration, occupants find themselves looking for comfortable and private environments to make calls and minimize distractions. Some offices also incorporate media production spaces for in-house marketing and content creation. As this trend continues, acoustics has become an essential element within the holistic and sustainable design of interior office spaces.
Interior Finishes
The selection of appropriate acoustic finishes supports the comfort and proper function of office environments. Acoustic finishes help control noise build-up, enhance speech intelligibility, and support audiovisual functions. The selection of high-performing sound-absorptive ceilings and carpet generally supports the use of most open and private office spaces. The need for sound-absorptive panels comes into play in boardrooms, conference rooms, huddle rooms, phone rooms, and media production spaces. Panels help address unwanted acoustic conditions generated by parallel walls, which can affect speech intelligibility and the use of audiovisual systems. The selection of acoustic materials is critical for spaces that have specific reverberation time requirements and specialty sound systems, which is generally the case for large, flexible multipurpose rooms.
Sound Isolation
Image Copyright Andrew Rugge/Perkins Eastman
The design of architectural assemblies is a critical component as it addresses speech privacy between spaces and the isolation of mechanical equipment noise. The client’s expectations regarding speech privacy help design teams define appropriate partition types, finished ceilings, door types, and door seals. The selection of high-performing glass office front systems along with fully framed doors with rubber seals is generally one of the first steps in selecting appropriate glass front systems. Frameless and sliding glass doors are typically not recommended for spaces requiring speech privacy. As glass and doors have acoustic limitations, the acoustic integrity of the design lies in the balanced selection of walls, office fronts, doors, and a thorough attention of their construction details.
MEP Systems Noise Control
Sound and vibration levels generated by mechanical, electrical, and plumbing (MEP) systems and elevators can cause disruptions, affect concentration, degrade speech intelligibility, and ultimately generate complaints. Unwanted sound levels can also impact older adults, and occupants with hearing impairments and neurodiversity. It is important to consider space adjacencies to base building equipment rooms. Locating noise-sensitive spaces away from base building or new equipment rooms can help avoid the need for expensive constructions. The location of supplemental equipment also needs to be carefully reviewed as those systems can end up located above occupied spaces and generate noisy conditions. Early planning, along with design guidelines and noise control treatments in accordance with the Noise & Vibration Chapter of the ASHRAE Handbook, are important to implement to help control MEP noise and vibration.
Speech Privacy
Nova Place, Pittsburgh PA
One of the most important acoustic design elements within a workplace is the intrusion of intelligible speech between enclosed spaces and from enclosed spaces to open collaboration areas. Speech privacy between private offices is also important, as it can also yield a different expectation. Speech privacy depends on the signal-to-noise ratio between the intruding speech level and the receiver’s background noise levels. The Speech Privacy Predictor (SPP) is generally used to analyze and establish specific acoustic design parameters to achieve the desired level of speech privacy. With a deeper dive into the SPP rating, speech privacy can be evaluated using the following factors*:
Speech Effort: The speech level generated by occupants in a source room. Conversational levels typically describe normal face-to-face conversations and people on web-conferences using headsets. Raised voice levels could be generated by occupants in large meeting spaces or by amplified voices through built-in computer speakers.
Source Room Floor Area: The effect of the sound absorption in the source room. A greater amount of noise build-up can be expected in smaller rooms, which can increase the signal transmitted. In large spaces, sound can be spread out and reduce the transmitted speech levels.
Sound Transmission Class (STC): This corresponds to the STC rating of specific partitions, office fronts, and doors separating two spaces. STC is typically used because it evaluates sound levels at speech frequencies.
Noise Reduction Factor: The effect of the sound absorption of the receiving room and the surface area of the barrier separating the two spaces. The size of the barrier and noise build-up in the receiver room can influence the amount of intruding speech.
Adjacent Room Background Noise Level (dBA): This represents the continuous steady state background noise level within a room. HVAC systems must be designed with appropriate background noise levels to complement speech privacy; spaces with very low background noise levels and inappropriate partitions can cause complaints. Balanced and properly designed HVAC systems generate background noise levels; however, mechanical noise does not generate an appropriate steady-state sound spectrum to cover up or mask intruding speech frequencies. The use of an electronic sound masking system can help achieve satisfactory levels of speech privacy as these systems introduce a properly tuned sound masking level. This type of sound covers up or masks intruding speech levels.
Achieving speech privacy starts with the selection of appropriate acoustic finishes to control noise build-up, the use of architectural assemblies to block intrusive speech, and a properly designed HVAC system that leads to occupant comfort. A well-designed and tuned sound masking system can achieve an appropriate amount of speech privacy, which ultimately leads to occupant satisfaction. With our field experience and data-driven tools, we assist design teams with the planning and implementation of these important acoustic design elements for our corporate clients.
At BABICHacoustics, we provide thorough acoustic design services from Planning and Programming through Construction Administration. Our goal is to create comfortable corporate acoustic environments that promote healthy and sustainable workspaces where people can collaborate, and businesses can grow.
*References:
Egan, M. D., Architectural Acoustics. New York, NY, McGraw Hill (1988).
Cavanaugh, W. J., Farrell, W. R., Hiertle, P. W., and Watters, B. G. Speech privacy in buildings. The Journal of the Acoustical Society of America 34, 475-492 (1962).
Salter, C., Powell K., Begault D., Alvarado R. Designing Acoustically Successful Workplaces: Case Studies of a Method for Predicting Speech Privacy in the Contemporary Workplace (2003).