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In a 2-year study conducted at Johns Hopkins Hospital in Baltimore, Md., acoustical engineers found that hospital noise is a top complaint of both staff and patients, but that little has been done to study the problem or lower the volume. Highlights of their study, which they presented at a meeting of the Acoustical Society of America, include the following:


* Average daytime hospital sound levels around the world have risen from 57 decibels to 72 decibels since 1960. Under World Health Organization guidelines, sound levels in patient rooms shouldn't exceed 35 decibels.

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* Worldwide, nighttime noise has jumped from 42 decibels to 60 decibels. Loud ventilation systems and equipment alarms contribute to the nighttime hubbub.


* Much hospital noise falls within the frequency range for human speech, making speech harder to hear and understand. To make themselves heard, people speak louder, adding to the din. The increasing use of automated systems that respond to voice commands also adds to the problem.



By making two small improvements, the researchers lowered noise levels in several patient care areas. In the pediatric intensive care unit, they discovered that staff members were paged an average of once every 5 minutes. After the researchers introduced hands-free personal communicators worn on a lanyard, the frequency of overhead pages dropped to about once an hour.


Researchers also found that many patient care areas lack sound-absorbing acoustical ceiling tiles, mainly because of infection control concerns. To address this shortcoming, they wrapped fiberglass insulation in antibacterial fabric and attached the insulation to ceilings and walls in an oncology unit. This improvement reduced sound reverberation by almost a factor of three.


Despite these successes, the researchers say that many noise problems, especially those involving loud ventilation systems, aren't easy to fix. They recommend that hospitals involve acoustics experts in renovations and the design of new facilities.