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 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 of the
Whiting School of
Engineering 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
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 The 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 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,
Busch-Vishniac is a professor of
engineering. West is a research professor in the
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
around the world have risen from 57 decibels to 72;
nighttime levels have jumped from 42 decibels to 60. All
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
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 acoustics experts
obtained modest reductions by making two small changes in
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
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 antibacterial fabric, then attached these
sound-absorbers to the ceiling and walls of a cancer unit
at the 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
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 the hospital. "They understood this as a patient
safety issue. Their expertise is what made the whole
Although these tactics were successful, West cautioned
that "the majority of hospital noise problems, particularly
involving the air handling systems, are not that easy to
fix." He and Busch-Vishniac said that 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
Funding for this research was provided by the Center
for Quality Improvements and Patient Safety of The Johns