Goodwin's High End


Room Soundproofing

An existing room will resist soundproofing efforts, making a good result both difficult and expensive. However, in new construction, you have a wonderful opportunity to create a quiet room for your enjoyment of music and perhaps movie soundtracks.

Even in a room with walls three feet thick, a small hole for an electrical wire will create an air leak. Sound will escape, thereby bypassing all the soundproofing efforts. Only great attention to detail in the design and construction of the room will result in a high level of sound isolation. During construction, a knowledgeable consultant should inspect the room at various stages to catch any potential problems. Remember: your contractor and subcontractors are not necessarily accustomed to constructing rooms with soundproofing in mind.

Key Point: Sound travels through the path of least resistance.

If you build extra thick walls, floor, and ceiling, less sound will travel in and out of your room. Going a step further, you can build a concrete slab on grade and then erect an exterior and interior shell on top of it. The interior walls and ceiling then don't touch the exterior shell, creating an entire "room within a room." Just as dual pane thermal window insulate against heat transmission, this construction will insulate against sound transmission. If you need an even higher level of soundproofing, we can design an isolated floor for your room. The floor and the interior shell of the room then "float" on the slab, isolating the room from floor-borne noise transmission.

An excessively soundproofed room can have another problem, however. If the walls, ceiling, and floor are too rigid or too massive, they will keep retain all of the speaker's bass in the room. Such a room will require much more extensive acoustic treatment to achieve a neutral tonal balance. So ideally you want the proper amount of mass that is not too rigid and does not act as a resonator.

With the basic sound isolation design complete, careful attention should turn to everything that penetrates the inner shell: doors, windows, electrical boxes, pipes, ducts, and so forth. Anything, no matter how large or small, that needs a hole cut in a wall, floor, or ceiling can create a flanking path for sound. We can specify special doors, windows, and skylights to mitigate sound transmission through these paths. Liberal and fastidious application of special acoustical caulk will both seal the room and provide anti-resonant sound isolation. This acoustical caulk remains pliable to provide a permanent air seal.

HVAC ducting provides a direct path for air to move in and out of the room. Designing bends in the ductwork, wrapping the exterior of the duct, and lining its interior will improve the soundproofing somewhat. "Home runs" of the ductwork back to the furnace or air handler will help. We can design a still air box with a great deal of sound absorbent material. Flexible ductwork junctions will isolate the ducts from the vibration of compressors, fans, and burners. Vibration generating equipment can be physically mounted on isolating rubber mounts.

Different construction techniques obviously yield varying amounts of sound isolation. Sound isolation is quantified by Sound Transmission Constant, or STC, as measured in decibels. For example, an STC of 60db would represent a high degree of soundproofing, whereas an STC of 30 would represent relatively little soundproofing. But if you have a wall that has an STC rating of 60 and a door with an STC rating of 30, you are wasting your money building the wall so well. It is important to have a balanced design and then to build it correctly. Because decibel scale is logarithmic, a difference of 30 db (60-30 = 30) represents a factor of 1000 a great difference indeed.

Typical residential doors and windows can leak a tremendous amount of sound. With careful planning, the doors and windows can be ordered with special materials so that they will create an airtight seal when closed. With high quality seals, proper installation, and perfect adjustment, these doors and windows will greatly enhance the soundproofing.

Glass such as windows, skylights, and sliding doors poses another challenge. Glass both resonates and reflects sound. Sometimes the glass can be eliminated without a loss of visual appeal. But natural light and fresh air can be wonderful. We can custom design your windows, skylights, and glass doors with extra thick specialty glass selected for its acoustical properties.

Soundproofing makes your room quieter for listening and allows you to listen without disturbing others, but to be effective it requires a comprehensive approach and diligent construction.

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