This article presents the results of a noise survey at Johns Hopkins Hospital in Baltimore, MD. Results include equivalent sound pressure levels (L(eq)) as a function of location, frequency, and time of day. At all locations and all times of day, the L(eq) indicate that a serious problem exists. No location is in compliance with current World Health Organization Guidelines, and a review of objective data indicates that this is true of hospitals throughout the world. Average equivalent sound levels are in the 50-60 dB(A) range for 1 min, 1/2, and 24 h averaging time periods. The spectra are generally flat over the 63-2000 Hz octave bands, with higher sound levels at lower frequencies, and a gradual roll off above 2000 Hz. Many units exhibit little if any reduction of sound levels in the nighttime. Data gathered at various hospitals over the last 45 years indicate a trend of increasing noise levels during daytime and nighttime hours. The implications of these results are significant for patients, visitors, and hospital staff.

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Most microelectromechanical systems (MEMS) designed today use macroscopic power supplies, thereby placing limits on the functionality of MEMS in many a pplications. An alternative to this approach is to design MEMS with integral, microscopic, distributed power supplies. This paper examines the feasibility of creating micropower supplies by considering three functions common to MEMS power systems: capture energy, store energy, a n d drive actuation. Of these, only the capture energy function is highly dependent on the speci c application. For each of the three functions, a table is presented which compares various means of performing the function. This information makes it possible to determine what design alternatives are feasible for creation of a micro power supply for any speci c application of MEMS. We use smart bearings with active surface features as an example application, and develop a design for a micro power supply suitable for this work.

Very little reliable information exists on the sound levels present in an operating room environment. To remedy this situation, sound pressure levels of the operating rooms in Johns Hopkins Hospital were monitored before, during, and after operations. The data were analyzed to determine background sound levels, average equivalent sound levels L(eq), frequency distribution, and peak sound pressure levels L(peak). Each surgery was matched to the period of noise it produced permitting the association of sound levels with particular types of surgeries and the determination of various sound measures for classes of surgery (e.g., orthopedic, neurological, etc.). Averaging over many surgeries, orthopedic surgery was found to have the highest L(eq) at approximately 66 dB(A). Neurosurgery, urology, cardiology, and gastrointestinal surgery followed closely, ranging from 62 to 65 dB(A). By considering the L(peak) along with the L(eq) values, a pattern emerges for the various surgical divisions. Gastrointestinal and thoracic surgery are relatively quiet among the surgical divisions. Neurosurgery and orthopedics have sustained high sound levels. Cardiology surgery has a more moderate average sound level but includes brief periods of extremely high peak sound levels. For neurosurgery and orthopedic surgery, peak levels exceeded 100 dB over 40% of the time. The highest peak levels routinely seen during surgery were well in excess of 120 dB.

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