April 24, 2008

For patients, silence is golden

  • Designers rethink how hospitals can cut noise and add privacy.


    As our crowded planet becomes increasingly louder, our sensitivity to noise from cars, construction equipment and even our coworker in the adjoining cubicle grows.

    The issue is of particular concern in hospitals, where studies have concluded that noise levels have risen an average of 0.35 decibels per year, in some cases putting them four times higher than suggested by the World Health Organization.

    While rumbling mechanical equipment and noisy activities at nurse stations can interrupt a patient’s sleep and interfere with the healing process, shielding a patient’s personal medical information from visitors and other patients is of equal importance. The Health Insurance Portability and Accountability Act (HIPAA) passed by Congress in 1996 addresses the issue of speech privacy and applies to anyone who handles personal health care information.

    The directives set forth by HIPAA — as well as numerous acoustical studies sponsored by various associations — all point towards an increase in sensitivity to noise and the need for a new approach to the design and construction of health care facilities. Subtle shifts in the layout of nurses’ stations or the design of admit areas can greatly reduce the amount of noise in the facilities and increase the level of privacy that patients deserve.

    New guidelines

    Image courtesy of Studio 216/NBBJ
    Nurses’ stations at Seattle’s Swedish Orthopedic Tower will have glass barriers and sound-absorbing materials in the ceiling and walls.

    The new Interim Sound and Vibration Design Guidelines for Hospital and Healthcare Facilities, recently approved by the American Hospital Board Association and the American Institute of Architects, addresses the increasing need for privacy and noise reduction in hospitals.

    While acoustical suggestions in earlier versions of the Guidelines for Design and Construction of Health Care Facilities were contained in a small table of limited information, the new acoustics guidelines are much more comprehensive, addressing site exterior noise, acoustical finishes and details, design criteria for room noise levels, sound isolation performance of construction, paging and call systems, and building vibration.

    These interim guidelines have been formally accepted by the Facility Guidelines Institute, which is responsible for the AIA guidelines. The next step is to integrate them into the next edition of the AIA guidelines in 2010. Until then, it is an “officially approved” set of design guidelines for hospitals and health care facilities.

    Furthermore, the U.S. Green Building Council adopted the interim guidelines as the basis for two new “environmental quality” credits in the LEED building rating system. The Green Guide for Health Care has already adopted the interim guidelines and offers two new credits under “environmental quality.”

    Two noise categories

    Noise in hospitals falls under two general categories: facility and operational noise.

    Facility noise is caused by mechanical, plumbing, electrical and other building systems, and includes exterior noise entering through the building envelope, as well as door-closing mechanisms.

    Operational noise, on the other hand, is associated with staff, patient and visitor activities, as well as medical equipment. Areas such as the pneumatic tube station, nourishment area (ice machine) and medication areas (automated dispensing systems) are key areas that produce noise that is unacceptable by minimal standards and affects the sleep patterns of patients.

    The new guidelines specifically address these categories with detailed tables and charts to help determine the allowable decibels of sound in certain areas of a facility.

    In the “site exterior noise” category, for example, a method for determining acoustical criteria for exterior walls is offered, based on the percentage of window area in the wall and the amplitude of the exterior noise.

    Detailed charts help users determine the appropriate sound transmission class (STC) rating. The STC is a single number rating for gauging the ability of a partition to reduce noise. It can be used to rank and compare doors, windows, enclosures, noise barriers and partitions. The rating (for example: STC-35, STC-40, STC-45) is expressed in terms of the products’ relative abilities to provide privacy against intrusion of speech sounds.

    Under the “acoustical finishes and details” section, the guidelines suggest that room finishes that absorb sound through the audible frequency range — such as suspended acoustical ceiling, sound absorptive wall panels, floor carpeting and draperies — be considered. Charts that outline the performance of specific finishes are offered to help designers choose the most appropriate material.

    Further, in the “building vibration” category, suggestions for peak velocity of floor vibrations in various hospital departments (patient areas, operating rooms, administrative areas and public circulation) are offered in a chart.

    Rethinking designs

    While these sound and vibration design guidelines do not require owners, architects and contractors to follow them until their integration into the AIA guidelines in 2010, they do underscore the importance of the design criteria typically set forth by acoustical engineers. In order to meet many of the new guidelines, project team members will — in many cases — have to rethink the way certain aspects of hospitals are typically designed and built.

    For example, the guidelines suggest that walls between patient rooms meet an STC-45 rating.

    Most partitions tested for acoustical performance are tested with a relatively light 25-gauge metal stud. However, heavier gauge metal studs — usually 20 gauge — are typically used in hospital construction to support furniture that is hung from the walls. A finished wall with a layer of sheetrock on each side of a 3 5/8-inch, 20-gauge stud would result in an STC rating of only 40; not the STC-45 the guidelines recommend.

    To meet the guidelines, another layer of sheetrock or a wider stud would have to be used. This could result in unexpected material costs or loss of floor space.

    The guidelines also address speech privacy, which — due to competing functions — is often compromised by the layout of admissions areas, nursing stations, and other areas in which medical records and other personal information are exchanged.

    The guidelines suggest specific STC ratings and speech privacy rating goals, depending on the type of room in question.

    Most intake areas are not designed to mask speech, and with family members and other patients often sitting nearby, confidentiality is compromised. Acoustical guidelines can be met by altering the design of these areas to include rooms with doors, or partitions with glass that still offer a level of openness while dampening speech. The incorporation of sound absorptive material on surfaces such as walls and ceilings can also weaken reflection and reduce overall noise.

    Hospital nurses’ stations are often designed and oriented to maximize the efficiency of the caregiver. Typically situated in the middle of a floor with patient rooms encircling them, the stations allow aides, nurses and doctors quick and easy access to their charges. However, with computer stations and other busy areas oriented directly towards the patient rooms, noise levels are often higher than recommended and impose on the patients’ comfort.

    Minimizing this noise is often as easy as reorienting certain task areas and adding sound absorptive materials and barriers.

    At the Swedish Orthopedic Tower currently under construction in Seattle, acoustical designers are using these techniques to reduce noise. While the station remains in the middle of the floor with patient rooms on each side, the active areas are directed away from patient rooms. Ceiling and back walls include sound-absorptive material to minimize noise, and glass barriers are added to further dampen sound.

    While the Interim Sound and Vibration Design Guidelines do not change the basic design principles acousticians have long followed, they do serve as a gentle reminder that our increasingly noisy world is slowly nudging the design and construction of health care facilities towards a new norm.

    Basel Jurdy, principal at Sparling, has worked professionally in mechanical equipment noise and vibration control, architectural acoustics, and environmental noise assessment for more than 18 years.

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