Noise levels in the Neonatal or Newborn Intensive Care Units of many hospitals are considered to be excessive. In some facilities, the sound levels are greatly in excess of the recommended levels. The highest nursery sound levels are typically found in crowded, multi-bed, Level III NICU’s.
While some newer NICU’s have private rooms, most NICU’s are multi-bed nurseries. It is simpler to achieve low noise levels in private rooms; however, acoustics is usually not factored into the decision making process when determining the format for a new NICU. Many other factors, such as floor area utilization, staffing requirements, ability of care givers to respond quickly, and encouraging family at the bedside take precedence. Regardless, the fact is that more patients in a room results in more noise in the room. And Level III NICU’s have more noisy medical equipment and more alarms. To achieve the lowest possible levels in multi-bed nurseries, many aspects of the design must be considered, including location of phones and hand wash stations, type of security door hardware and location of secured doors, partition acoustic ratings, and the sound attenuation incorporated into the HVAC system. To many designers, the most obvious consideration is the ceiling type. How much sound absorption should be provided by the ceiling?
The ASHE/FGI 2010 Guidelines for the Design and Construction of Health Care Facilities states that 80% of ceiling area in a NICU should have a Noise Reduction Coefficient (NRC) of 0.95 or higher or that the entire ceiling area should have an NRC of 0.85 or higher. This is a high NRC. The majority of acoustical ceiling tiles have an NRC in the range of 0.50 to 0.70. The 2010 Guidelines for the Design and Construction of Health Care Facilities also calls for the ceiling to have a Ceiling Attenuation Class (CAC) of 29 or higher and rightly states that there are very few acoustical ceiling tiles that have both a minimum CAC of 29 and an NRC of 0.95. Designers have very limited options for NICU ceilings. However, I disagree with the blanket requirement to use tiles with a minimum CAC of 29. CAC is a measure of how much sound is blocked by a ceiling tile. If wall partitions between the nursery and adjacent rooms are only partial height (extend to just above the ceiling rather than to the underside of the deck above) then tiles with a higher CAC will reduce the amount of noise transferred over the top of the partitions. If there is loud mechanical equipment in the ceiling void above the NICU then tiles with a high CAC will reduce the amount of mechanical noise transmitted through the ceiling. However, a thorough acoustical review of the project can determine which walls need to be full height and how they should be constructed. It will also estimate the amount of noise that will be created by mechanical equipment in the ceiling void. By conducting a thorough acoustical review, it may sometimes be possible to eliminate the CAC requirement.
In addition to these acoustical ceiling requirements, the 2010 Guide also suggests that sound absorbing wall panels be placed on two perpendicular walls or along the top of all walls. In suggesting this wall treatment rather than requiring it, the Guide appears to recognize that there is limited wall area in a multi-bed NICU which can be finished with acoustical wall panels.
The use of sound absorbing finishes is of obvious importance to the acoustical environment. Perhaps of less obvious importance is the patient density in multi-bed nurseries. The Guide calls for a minimum distance of 8 feet between infants. If the baby and family are only eight feet from the adjacent baby and family then the type of acoustical ceiling tile above them will have limited impact on the sound transmitted from one to the other. To reduce this “direct sound,” patient density can be reduced so that there is more distance between infants. Also, partial height partitions or sliding dividers can be used so that noise does not have a direct ine of travel between beds. Eliminating the direct line of travel increases the effectiveness of the sound absorbing room finishes.
Using sound absorbing finishes, decreasing patient density, and using sound barriers between beds are important factors in determining the NICU soundscape. In future blog entries I will discuss the many other NICU noise sources and means of attenuation.
Whether you’re located in Chicago or elsewhere, if you are designing a new NICU or need an acoustical expert to help assess noise in an existing NICU, you can contact me at Soundscape Engineering (http://www.SoundscapeEngineering.com).