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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).

noise in and around a home

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.

Table 1: Generally Required and Suggested Minimum STC and IIC for Occupant Satisfaction For Various Structural Elements.

Structural Element

Generally Required STC

Suggested Minimum STC

Suggested Minimum IIC

Party walls or floors



- -

Bare party floors




Carpeted party floors




Elevator shafts



- -

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.


Area Problem Cause

Walls, Floors & Ceiling

Sound / noise intrusion from an adjoining apartment

A deficiency in the party wall

Kitchen, bathroom and entertainment sounds and noises are clearly audible in the "quiet" areas of home or a neighboring apartment

Poor layout:  Noisy rooms are beside quiet rooms.

Insufficient sound and noise reduction, even through the wood-stud wall contains sound-absorbing material.

Drywall directly attached to the wood studs on both sides of the wall.

Unknown design or construction error. Existing wall cannot be disturbed.

Mounting drywall on resilient metal furring does not sufficiently reduce sound and noise transmission.

Drywall screws that are too long, "short-circuiting" the resilient metal furring.

Resilient metal furring between two layers of drywall, forming a small air space with a solid connection of the inner layer to the studs

Sound and noise leaking close to the floor wall junction.

No sealant under the sole plate

Sealant not effective because of debris under the sole plates.

Improper seal between the drywall and bottom wall plate or bottom metal track.

Sound and noise leaking through electrical receptacles.

Unsealed, back-to-back electrical receptacles

Concrete block wall not providing sufficient sound proofing or noise reduction.

Concrete blocks are porous and will let some sound pass through.

No seal at the foot of a block wall finished with drywall

Drywall too close to concrete blocks.

Poured concrete wall does not provide adequate sound proofing or noise reduction.

Holes or honeycomb penetrations in the structure

Holes or honeycomb penetrations in the structure and no seal at the foot of the drywall.

Poor sound proofing or noise reduction from a lightweight floor system.

Ceiling directly attached to the floor joists.

Poor sealing at edges of ceiling

Flooring with acoustic ceiling not providing enough sound proofing or noise reduction from storey above.

No effective sound barrier in ceiling

Flooring not providing enough insulation form impact sound and noise.

Upper layer not heavy enough or no direct absorbing of impacts.

Floating flooring not providing expected sound proofing or noise reduction.

Floor contacting structure at edges

Flanking Sound

Good wall design but poor sound proofing and noise reduction

Flanking transmission along the top layer of a concrete floor.

Flanking transmission along the top layer of a wood floor.

Transmission through the floor into the common cavity underneath.

Flanking transmission through the attic space.

Flanking transmissions along single continuous layers of drywall on walls at right angles to the party wall or floor.

Excessive sound and noise transmission through the flooring, especially footstep and impact sound.

Flanking transmission down the walls

Excessive sound and noise transmission between bathrooms.

Drywall behind bathtubs is not extended completely to the floor.

Bathroom cabinets are mounted back-to-back on a common wall.

Sound and noise leaks around pipes

Plumbing Noise

Plumbing sounds and noises heard all over the house or apartment and in adjoining rooms.

Pipes rigidly connected to walls.

Turbulence caused by high water-pressure and an excessive number of elbows and bends.

Turbulence from noisy valves and fixtures

Bath, shower and toilet sounds and noises heard in neighboring rooms or apartments

Waste pipes installed close to quiet areas.

Bathtub, shower or toilet rigidly attached to building structure,

A noisy toilet solidly connected to the floor.

Loud banging when, faucets are closed, dishwasher, clothes washing machine valves operate

Water hammer-shock waves generated when valves close to rapidly.

External Sounds & Noise

Outdoor sound and noise penetration into the home

Windows left open to provide ventilation. At noisy sites, windows must be closed for acceptable sound and noise reduction.

Sound and noise leaks around windows or doors

Sound and noise transmitted through an inadequate window

Sound and noise transmitted through an inadequate door.

Sound and noise transmitted through an exterior wall.

Sound and noise transmitted through the roof or ceiling

Outdoor Appliances

Sound and noise annoys neighbors

Sound and noise from an appliance is a quiet neighborhood

Appliance in a poor location

Poor location or noisy appliance

Indoor Appliances

Sound and noise from a forced-air furnace

The fan or combustion systems for some modern high-efficiency furnaces are noisy.

Ducts creak or bang when furnace cycles on and off

Expansion and contraction

Noisy appliances (dishwasher, washing machine)

Load noise generation, poor location, poor insulation

Noisy ventilation equipment

Fan equipment

Ducts carry sound

Ventilation equipment connected directly to the building's structure.