Introduction To Sound Proofing & Noise Control

Sound and noise - whether it originates inside or out - is an unwelcome intruder in any home. It devalues privacy and indeed the worth of the building itself. Unwanted sound and noise has many sources: noisy plumbing and neighbors' stereos are two examples.

Materials used in construction help reduce sound and noise in two distinct ways; they can absorb sound waves or they can act as barriers against their transmission. Sound-absorbing materials such as carpets and acoustic ceiling tiles, can effectively muffle sound and noise generated in a room. To reduce sound and noise transmission between rooms or stories, sound-absorbing materials in the cavity of the barrier walls or floors will do the best job. The common thermal insulations (cellulose fiber, mineral fiber, and some open cell foams are good sound absorbers for barrier cavities, while closed-cell foams such as polystyrene and polyurethane generally are not.

Drywall, plywood, concrete and glass are good sound barriers.

The decibel is the standard measure of loudness. The Sound Transmission Class (STC) indicates the average sound/noise reduction in decibels for sounds passing through walls or floors. The higher the STC, the greater the sound and noise reduction. For example, an STC60 wall would let 10 times less sound through than an STC 50 wall. The ear would perceive this as half the sound coming through, so the STC 60 wall is perceived as being twice as good as the STC 50 wall.

Floors receive a similar rating, called the Impact Insulation Class (IIC).

Most building codes require a minimum STC of 50 for common walls and floors. Builders should provide a STC 55 to ensure good acoustic privacy. Where exceptional sound isolation is desired, STC 60 is a more appropriate goal. Table 1 gives both the generally required and some suggested minimum STC and ICC values.

This section is an introduction to sound and noise control. It deals mainly with common lightweight or porous constructions - wood - or steel frame, or concrete block - since these can easily provide very good sound and noise control but are also easily spoiled by small oversights or errors.

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