Acoustics experts say medical sound pollution is widely recognized, rarely addressed

Nov 21 2005

Announcements blare from overhead speakers. Electronic devices beep. Heating and cooling systems rumble. Employees and visitors speak loudly.

This sound snapshot, researchers say, comes not from a factory or a sports stadium but from a typical hospital. In a new study, Johns Hopkins University acoustical engineers found that hospital noise levels internationally have grown steadily over the past five decades, disturbing patients and staff members, raising the risk of medical errors and hindering efforts to modernize hospitals with speech recognition systems. Some studies even indicate that excessive noise can slow the pace of healing and contribute to stress and burnout among hospital workers.

During a two-year research project, acoustics experts Ilene Busch-Vishniac and James E. West learned that hospital noise is among the top complaints of both patients and hospital staff members, but that little is being done to address the problem. The researchers found that scientific studies of hospital noise were scarce, and that most had been conducted by medical personnel, not acoustical engineers.

"That told us this problem was important enough that the doctors and nurses were willing to step outside their comfort zone to make some noise measurements, even though they didn't always know how to analyze the data correctly," Busch-Vishniac said. "Acoustical engineers needed to get involved, and it was long overdue. We believe that funding is needed to broaden fundamental research in this area."

Added West: "People have been complaining about hospital noise for years, but little has been done about the problem."

In 2003, when Stephanie L. Reel, vice president and chief information officer for Johns Hopkins Medicine, called their attention to noise levels in the pediatric intensive care unit at Johns Hopkins Hospital, Busch-Vishniac and West agreed to investigate. The researchers surveyed the handful of published reports on hospital noise from the past half-century and made their own sound measurements in several patient areas at Johns Hopkins. The Baltimore hospital, which provided financial and staff support, also allowed Busch-Vishniac and West to test two techniques that helped reduce noise in some patient areas.

What made their work so different from past research was that it partnered the medical professionals and the acoustical engineers, first to characterize the hospital sound environment and then to find ways to lessen the impact of sound.

"This study focused on a very real challenge," Reel said. "A noisy intensive care unit introduces patient, family and staff dissatisfaction. It has also been reported that noise can contribute to lapses in short-term memory, which could then introduce safety concerns. Ilene and Jim recognized the importance of this issue and worked with us to address the immediate needs of this pediatric intensive care unit. They also gave us terrific recommendations for the new clinical buildings that will be constructed over the next few years."

The researchers believe their findings have important implications for hospitals worldwide. West and Busch-Vishniac presented their conclusions at the annual meeting of the Acoustical Society of America, held recently in Minneapolis. A paper based on their work will appear in an upcoming issue of the Journal of the Acoustical Society of America. West and Busch-Vishniac are both past presidents of the society. At Johns Hopkins University, Busch-Vishniac is a professor of mechanical engineering. West is a research professor in the Department of Electrical and Computer Engineering. He also is a member of the National Academy of Engineering.

Following are some highlights from their study:

• Since 1960, average daytime hospital sound levels around the world have risen from 57 decibels to 72; nighttime levels have jumped from 42 decibels to 60. All of these figures exceed the World Health Organization's 1995 hospital noise guidelines, which suggest that sound levels in patient rooms should not exceed 35 decibels. The measurements vary little among different types of hospitals, indicating the problem is pervasive.

• Much of hospital noise falls in the human speech frequency range, making oral communication more difficult. This can force doctors and nurses to speak even louder to be heard, further boosting the noise level. Sound congestion could lead to a misunderstanding of spoken orders for tests and medication, the researchers said. In addition, many hospitals are moving to more automated systems, in which equipment responds to voice commands. But amid a clutter of sound in the human voice frequencies, voice recognition software does not work well.
• In many hospital units, noise does not take a break at sunset. Measurements made by Busch-Vishniac and West indicated that noise levels remain high around the clock. This was attributed partly to hospital ventilation systems that run at powerful settings and to a proliferation of alarm-laden electronic devices.

Can anything be done to reduce hospital noise? Although the problem is complex, the Johns Hopkins acoustics experts obtained modest reductions by making two small changes in patient areas.

In the pediatric intensive care ward, hospital personnel were paged an average of every five minutes via overhead loudspeakers. Busch-Vishniac and West introduced the staff to small hands-free personal communicators, worn on a lanyard. The communicators operate like cell phones, and each staff member can be signaled directly and quietly. This system cut the frequency of overhead pages to about once an hour. The system was initially used during a two-month trial run, but staff members were so pleased by the results that the hospital purchased the system for that unit.

The researchers also found that acoustical ceiling tiles, a common sound-absorbing furnishing, are often absent from patient areas because they can provide a hiding place for infectious organisms. To address this concern, Busch-Vishniac and West wrapped fiberglass insulation inside an anti-bacterial fabric, then attached these sound-absorbers to the ceiling and walls of a cancer unit at Johns Hopkins Hospital. This measure suppressed some sounds that previously bounced around the room. "Our treatment reduced the reverberation time by almost a factor of three," West said.

Hospital staff members were pleased by the reduction in noise. "We could not have done this without their expertise as acoustical engineers," said Sharon Krumm, administrator and director of nursing for the Kimmel Cancer Center at Johns Hopkins Hospital. "They understood this as a patient safety issue. Their expertise is what made the whole outcome possible."

Although these tactics were successful, West cautioned that "the majority of hospital noise problems, particularly involving the air handlings systems, are not that easy to fix." He and Busch-Vishniac said long-range solutions will require that skilled acoustics experts and architects work closely together to reduce noise problems when planning future hospitals and renovations of existing medical centers.