Noise and Odor Control Using proven methods of sound control in concert with a well-designed mechanical system and a sanitary environment, noise and odor control can be achieved. NOISE CONTROL The five areas of focus when controlling noise in veterinary facilities are absorption, isolation, dissipation, masking, and design of the HVAC system. A discussion of these areas of interest follows: Absorption The first line of defense in controlling noise is to absorb the noise as close to the source as possible. The more surface area of absorbent material you have, the better off you will be. Unfortunately, the typical absorbent material is not very cleanable or durable, so you are faced with a dilemma. How do you absorb sound while providing a clean, aseptic environment? In looking at materials to be used to absorb sound, you are looking for a material with a high Noise Reduction Coefficient (NRC) rating. The NRC rating quantifies the amount of noise a material absorbs. For example, a ceiling tile of .65 NRC means that it absorbs 65 percent of the reverberant noise that hits the tile. An NRC of 1.0 means it absorbs 100 percent. For the most part, you want to aim for materials with an NRC of approximately .75 to 1.0. In contrast, concrete block walls and concrete floors have an NRC of .00 to .1! The following materials can be used to absorb sound and are at least somewhat cleanable:
Isolation Given that you can’t absorb all the sound that is produced by the animals, the next goal is to isolate the sound before it spreads. The best way to do this is to build your facility without holes for the sound to escape and of sufficient density to eliminate the transmission of noise. In looking at the isolation of noise, there is a Sound Transmission Class (STC) rating that is used to describe how much noise passes through a given assembly. The STC rating is equivalent to the number of decibels of sound that the assembly screens out. For example, a wall with an STC of 45 means that it will screen out approximately 45 decibels of sound, or the equivalent of a normal person talking. To give some perspective, a dog barks in the range of 100 or more decibels. This means that to effectively screen out all sound from a run, you would need to build a wall with an STC of 100. While this is not feasible, it is also not necessary. The highest effective STC that can be gained in a normal wall is approximately 55 to 65. For the most part, this is workable, because of the remaining sound that escapes, approximately 35 decibels, will be masked by normal background sound. In addition to creating a wall that has enough mass to isolate the noise, it is also very important to eliminate any holes through the wall or any paths where noise can “flank” the wall. For example, a two-inch square opening through a wall can completely negate the sound isolation capabilities of the balance of the wall. Going a little further with this concept, you can also see that a window in a wall or a door in a wall with a gap around it can significantly reduce the total effectiveness of the wall. Another common mistake in building sound isolation walls is to not extend the walls above the ceiling. When walls are not tight to the roof deck, sound can escape by “flanking” up and over the ceiling and then dropping back into the adjacent room. A listing of typical assemblies and their STC follows:
The isolation abilities of a wall can be increased by increasing the mass of the wall, adding layers to the wall, breaking the way vibration can track through a wall or ceiling, and by filling any openings you might have. Dissipation Another way to control noise is to allow it to dissipate. In a larger room, noise can die off before it hits a wall and bounces back. In the outdoors where there are no walls, sound will die off at the inverse square of the distance. This means that theoretically the sound will die off to nothing in a very short distance. Inside, it is virtually impossible to create a space big enough for sound to die off naturally, but by increasing the height of a room and adding as much absorption as possible, you can move toward this goal. Masking Masking is your last resort if you cannot absorb, isolate, or dissipate the noise. The perception of a noise problem is very much based on the context within which people perceive the noise. It is hard to be bothered by noise from an adjacent space if the noise in the space in which you are located is high. This is why it is okay to have a dog kennel located adjacent next to a nightclub, but not a library. In your facility, Muzak or a sound system can do a lot to mask noise coming from the animal areas. Coincidentally, it has been proven that Muzak in the animal holding areas can actually calm the animals. HVAC System Considerations Ducts penetrating from one sound area to another can be a possible source of sound or noise leakage. A ceiling penetration with a diffuser or grille will also allow sound to migrate to another room in the same sound area. ODOR CONTROL Odor can be controlled through:
Odor control can be best accomplished by eliminating the source. Frequent cleaning of the runs and cage areas is the first and most obvious step in the control of odor. Locate water hose bibbs in convenient locations. When things are easy to use, the job gets done more efficiently. Floor drains with hinged covers or trenches located at the back of the runs are convenient ways to dispose of solid waste. Any odor should be contained within its own area. This can be accomplished through the use of positive and negative air pressure. Negative pressure areas will hold odors, and positive pressure areas will not allow odors to enter. You want your facility to have the areas of least odor in the client areas and contain the most odor in the ward and run areas. This can be accomplished by creating positive pressure in the client and staff areas and creating negative pressure in the animal areas. If you supply more outside air than you exhaust, it will create a positive pressure area. If you exhaust more air than you supply, it will create a negative pressure area. Outside air provides new, odorless air into the facility to help create an odor-free environment. Air-conditioning systems provide a ducted air supply with either duct return air or plenum (ceiling space) return air. In order to maintain pressure relationships, the air-conditioning system must have a ducted and well-balanced return air system. The pressure relationship between areas is critical to odor control. We recommend using an experienced person who can design an effective system. Here are some general criteria for pressure relationships:
Another way to control odor in your facility is to exhaust the unclean air. Exhaust fans should be provided for the following areas:
Lastly, there are a number of electronic deodorizer and disinfectant systems on the market. Generally, we don’t recommend them, because they can be expensive and are, depending on who you talk to, ineffective. Specific systems should be individually evaluated by seeing them and/or speaking to someone who already has the particular one you are interested in. |
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