Page 46 - January 2006

Echoes from Minneapolis
What Do We Know About Noise in Hospitals?
James E. West and Ilene J. Busch-Vishniac
The importance of noise in health care has been rec- ognized for years but little work has been done to charac- terize and reduce hospital noise even though it routinely ranks among the top complaints of hospital patients, vis- itors and staff. There are a small number of hospital noise surveys in the scientific literature. This body of literature suggests that a significant problem exists, and that it is generally getting worse rather than better, even in new construction.
Noise in hospitals is important for a number of rea- sons in addition to the obvious issue of annoyance. There is evidence that the high sound levels in the hospital con- tribute to stress and burn-out in hospital staff. Further, there is some evidence that noise negatively affects the speed of wound healing. Additionally, there is legitimate concern that hospital noise could negatively affect speech communication and cause increased numbers of medical errors.
We reviewed the literature carefully to enable us to answer the following basic questions: Is there any indica- tion that hospital noise levels are changing over time? Do hospital noise levels vary dramatically from hospital to hospital? Do hospital noise levels vary significantly with type of unit?
Fig. 1. A-weighted equivalent sound pressure levels measured in hospitals during the day as a function of the year of study publication
The graph below shows the results of our compila- tion of existing noise studies by showing the A-weighted equivalent sound level as a function of the year of publi- cation of the study. A-weighting corrects for the pitch response characteristics of humans, and equivalent sound pressure levels are the sound levels that would be produced if time-varying sound instead had a constant level producing the same total sound energy.
There are three interesting points raised by this liter- ature survey. First, not one published result shows a hos- pital which complies with established standards for hos- pital noise. These standards were developed to define maximum noise levels commensurate with health care purposes. Most of the data, particularly that which is recent, shows sound levels 20-40 dB(A) higher, i.e. 2 – 4 orders of magnitude more energetic than the standards suggest. Second, there is a clear trend for rising hospital noise levels consistently since 1960. A straight line fit to the data (included in the figure) shows an increase, on average, of 0.38 dB per year for daytime levels. Thus, the situation has been steadily worsening. Third, the figure shows remarkably little variation given that the results are for widely different sorts of hospitals (major research facilities to community hospitals) located throughout the
44 Acoustics Today, January 2006