Share thisThis is a phrase we are hearing more and more. The reason usually relates to excessive room noise. All too frequently, and especially in new construction, we are running into rooms or laboratories that present problems with normal conversations. Typically, this results from ventilation systems. In our attempts to ensure adequate fresh air and acceptable indoor environmental quality while reducing construction costs, the heating, ventilating and air conditioning (HVAC) system struggles with the air flows. The ducts often end up undersized for the volumes handled and can lead to vibration and noise that interferes with speech and communication. This situation can be especially problematic in animal care facilities where we are scrubbing or filtering the air supply with high efficiency particulate air (HEPA) filters and trying to balance flows in ventilated rack systems. The more advanced the air supply and filtering system becomes the more potential for these types of problems. Add this to the noise induced by our normal work activities and we likely have conditions that can make every day hearing difficult.
Excess noise is not a good thing. Background noise from HVAC systems or other building activities can become insidious. It can make conversation difficult, affect concentration, distract workers, and increase fatigue not to mention the potential adverse affects on the research animals. How do we know if the noise is excessive? One rule of thumb is if normal conversation or talking on the telephone is difficult or impossible. A better way is to have the area assessed by someone knowledgeable about sound, its measurement techniques, and data interpretation, such as an industrial hygienist or acoustical engineer. The National Institute of Health Office of Research Facilities recommends a maximum noise level of NC-45 in operating rooms, research laboratories, and research animal housing areas for reasonable speech communication.1NC-45 refers to a balanced noise criterion curve which is a set of octave band sound pressure levels used to characterize the noise in a space. (More on NC curves later.) It is important to keep in mind that the NIH recommendation is for worker conversation.
NIH goes on to say that when evaluating noise in research animal housing areas you should consider both the people and the animals in these spaces. Most recent research in this area recommends that noise levels should be species specific for animal housing spaces, but it is hard to find what those levels should be as this is a relatively new area of research. Animals and animal care activities produce noise inherently during normal functioning of the facility. For this reason, noise control should appear high on the list throughout facility design as well as operation. The National Research Council states that assessment of potential effects of noise on animals consider intensity, frequency, rapidity of onset, duration, vibration, hearing range, noise exposure history, and sound-effect susceptibility of the species, stock or strain.2NRC recommends separation of human and animal areas to minimize disturbances to both. In addition, noisy animals such as dogs, swine, and primates should be housed well away from quieter animals such as rodents, rabbits, and cats.