August 25, 2005

Silence is golden — but rare — in a hospital

  • Designers can take steps to reduce hospital noise
    Yantis Acoustical Design


    Unnecessary hospital noise has been called the cruelest absence of care.

    But what about noise related to vital hospital functions? How can background noise be managed to improve patient healing?

    Mechanical ventilation systems, medical equipment noise and nursing stations impact patient rooms. Add in street traffic, overhead paging systems and "cross-talk" from staff, visitors and televisions, and you have a noisy healing environment.

    In addition, maternity wards have special noise considerations. Excessive background noise in neonatal intensive care units (NICUs), for example, has been recently linked to development problems in premature infants.

    Plan for noise

    Controlling mechanical and building noise is a complex process that requires close coordination among the design team. While a certain amount of noise in patient rooms is inevitable, there are special considerations that can help lessen its presence and make it more tolerable.

    Controlling noise begins with the design team and evolves into a hospital-wide culture

    Mechanical system capacity, airflow rate and fan pressure have increased in recent years due to increased requirements in air filtration and air volume changes. These factors have made main fan systems noisier.

    The space above each patient room ceiling has a supply air terminal box that controls the airflow volume and temperature serving the room. Some rooms require an additional air terminal box in the return duct to help regulate the room's air pressure. These boxes bring noise closer to the patients.

    Most medical facilities have eliminated internal fiberglass lining from their ductwork as part of their indoor air quality control. This lining was at one time an effective noise-control measure.

    Acousticians must now control noise in other ways. Duct silencers and other devices can mitigate noise, but add to the initial and operating costs of a building.

    The location of emergency generators has a tremendous impact on patient room background noise and other occupants.

    For example, emergency generators (which most hospitals test weekly) can easily exceed 100 decibels if left unmitigated. While these and other systems are ideally located in an adjacent central plant or on site, not every facility has this luxury. Furthermore, the operation of emergency generators is not always limited to power outages and routine maintenance.

    If designed for peak-shaving or dispatchable power, generators could run for several hours or days in a row, which can be very disturbing to patients in nearby spaces and can impact neighboring properties. Noise-control measures for these systems can require extra space and should be addressed early in the design process.

    Acoustic ceiling tiles with good sound-absorptive capabilities are better than sheetrock for reducing sound within rooms. While sheetrock yields a more seamless appearance, it reflects and exaggerates sound.

    Vibration control

    Vibration issues should be addressed early in the schematic design, as vibration control can dramatically impact the structure of the building. Surgery suites, imaging equipment and areas with analysis microscopes require low levels of floor vibration.

    Facilities with rooftop helipads should take special care to address how vibrations from helicopters affect building occupants and functions, particularly surgery suites.

    Magnetic resonance imaging technology introduces another source of vibration. Today most clinics have an MRI, and hospitals have several.

    MRIs are loud acoustically and vibrationally. They are sensitive to ambient floor vibration and are capable of increasing the floor vibration due to their own operation.

    Working with the structural engineer, acousticians can perform a finite element analysis model on the proposed floor to determine if it is optimal for MRI use. Modifications to the design, if needed, can be coordinated with the structural engineer.

    To contain the noise, walls and ceilings can be designed specifically for the MRI.

    Mechanical equipment such as fans, chillers, pumps and compressors also produces noise and vibration. The location of this equipment can reduce its impact on the hospital, as can proper vibration-isolation procedures.

    Training tips

    Beyond what acousticians bring to the table, staff education and behavior modification are important in the effort to reduce background noise in hospitals. Here are a few suggestions for hospitals to follow:

    — Noise is most successfully controlled at its source. Staff should be trained to maintain low voice levels at all times.

    — Ongoing education about reduced noise levels in NICUs should include low vocal efforts; use of quiet medical equipment, cabinets and drawers; muted pagers and cell phones; and control of the hospital's overhead paging system so it is not audible in the NICU.

    — At nursing stations, encourage the use of phones with headsets.

    — Close patient room doors. This can go a long way toward controlling noise from hallways and nursing stations. To ease patient concern, let them know that they are being monitored 24/7 even though their door is closed.

    — Turn off the overhead paging system at night, and limit use of the paging system to areas other than patient rooms and hallways. A personnel locator or pager system should be considered to permit quiet communication among staff.

    — Purchase medical equipment or modify existing equipment to enable volume control of alarms and other sounds associated with medical equipment.

    — In patient rooms, use pillow speakers for TVs, radios and intercom communication.

    Controlling background noise in hospitals is an ongoing collaborative goal. It begins with the design team in the early stages of the building development, and evolves into a hospital-wide culture of providing a quiet and healing environment for patients.

    Basel H. Jurdy is a principal of Yantis Acoustical Design in Seattle.

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