Did You Know?

A large meal will temporarily make your hearing less sharp.

STC Ratings Simply Put

Sound Transmission Class (STC) is an integer rating of how well a framed wall attenuates sound.

• Doubling the mass of a wall assembly does not double the STC

• An empty framed wall (steel studs and a layer of gypsum wallboard on each side) has an STC of approximately 35dB

• Adding an additional layer of gypsum wallboard (from two sheets to four sheets) increases the STC by about 5–6 points

• Adding cavity insulation increases the STC approximately 4–6 dB

• Fiberglass batts increase the STC to 39; Cellulose insulation increases the STC to 44

• Batt insulation must fit tight without gaps

• Batt thickness provides better sound control than batt density. Compressing a batt reduces STC and thermal efficiency

• Stud assembly must span from deck to ceiling

• Structurally decoupling the gypsum wallboard panels from each other, like using a staggered stud assembly

or a double stud wall) can yield an STC as high as 63 or more

•Also materials such as United Plastics Corporation's dB-3PRO along with gypsum wallboard and insullation may also improve STC ratings (Refer to manufacturer specifications)

How Loud is TOO LOUD

Standards set by OSHA (Occupational Safety and Health Administration) indicate that continued exposure to noise over 85 dBA will eventually harm hearing. According to OSHA, the exposure time allowed is cut in half for every 5 decibel increase. For example, if a sound is 95 dBA, then 4 hours of exposure, over time, will cause hearing loss, and exposure to sounds at 115 dBA for just 15 minutes a day, over time, will cause hearing loss. Other groups, such as NIOSH (National Institute for Occupational Safety and Health) calculate safe exposure time by decreasing time in half for every 3 decibel increase. The NHCA (National Hearing Conservation Association) is an excellent resource for more information about occupational hearing conservation programs.

Will this really control sound?

Resilient channel is a specially-formed, metal device that, when used to hang drywall (instead of attaching the drywall directly to the wall studs or ceiling joists), significantly reduces the sound transmission of the wall or ceiling system. The channel material is secured to the studs and drywall is secured to the channel - providing a break in sound transmission through the wall.

Resilient channel for sound control is not effective if attached to sheet materials, such as drywall. It is also important to use the right length screws, so they do not penetrate into the wood framing.

Just a few screws into the wood can undermine the resilient connection and substantially lower the STC and IIC ratings.

Did you know?

Resilient Channel was not originally designed to provide improved sound attenuation, but rather to avoid cracks in drywall? 

More and more States are adopting ordinances for dealing with sound

Here is an example of what one state is doing:

Table 1 - State noise guidelines.

State Department of Health and County Liquor Commission Maximum Permissible Noise Limits
Zoning Districts:	Daytime (7:00 am to 10:00 pm)	Nighttime (10:00 pm to 7:00 am)
Residential, Conservation, Preservation, Public/Open Space	55 dBA	45 dBA
Multi-Family Dwellings, Apartments, Business, Commercial, Hotel, Resort	60 dBA	50 dBA
Agriculture, Country, Industrial	70 dBA	70 dBA
County Land Use Commission Special Ordinance for Outdoor Amphitheater
Nearest Apartment/Hotel/Business (approximately 2000 feet away)	68 dBA	Prohibited

How does NOISE effect us in everyday life?

When unwanted sound created by human beings hits our ears and disturbs the environment, noise pollution is created. Chiefly, noise pollution comes from barking dogs, loud music, vehicles, aircraft and rail transport, air-conditioners, factories, amplified music and construction work.
Sources of noise: All transportation systems create noise pollution. With residences created adjacent to factories, they experience noise pollution and its adverse effects. Besides transportation noise, noise can come from factory appliances, power tools and audio entertainment systems.
Measures of noise: Noise pollution is measured in decibels. When noise is at 45 decibels, no human being can sleep, and at 120 decibels the ear is in pain and hearing begins to be damaged at 85 decibels.
Effects of noise pollution
Human health: Noise pollution disturbs our health and behavior in a number of ways including deafness causing lack of sleep, irritability, indigestion, heartburn, high blood pressure, ulcers, and heart disease. Just one noise explosion from a passing truck drastically alters our endocrinal, neurological, and cardiovascular functions in many individuals. If this is prolonged or frequent, the physiological disturbances become chronic and contribute to mental illness.
Annoyance: Sometimes, even low levels of noise are irritating and can be frustrating, and high volumes can be annoying. Natural sounds are less irritating than those we find uncontrollable but intermittent sounds such as a tap dripping water can be more irritating than the sound of falling rain.

Here Are A Few Examples Of Sounds Effects on Education and Healthcare

Noise Levels In Education

Cognitive development is impaired when homes or schools are near sources of noise such as highways and airports.

Noise affects learning, reading, problem solving, motivation, school performance, and social and emotional development.

Children who live in noisy environments have been shown to have elevated blood pressures and elevated levels of stress-induced hormones.

 American National Standards Institute calls for a maximum ambient noise level of 35 dB.

 Many classrooms currently do not meet the recommendations of this standard, but at least one state, Connecticut, has already adopted the use of ANSI S12.60 for its schools.

Noise Levels In Healthcare

Excessive noise, and its effect on rest, are high on the list of complaints made by patients on post-discharge patient satisfaction surveys.

Excessive noise in health care settings can induce headaches, cause irritability, prolong wound healing and increase sensitivity to pain.

Noise levels in hospitals are twice what they were a few decades ago. They're approaching the level of harm, and they're definitely at the level of stress.

Health care is noisier than ever. Worldwide, the sound levels inside hospitals average 72 decibels during the day and 60 decibels at night — far exceeding the standard of 40 decibels or less, set by the World Health Organization.

 Did you know ... ? Tapping on the top of an incubator is equivalent to the sounds of heavy traffic during rush hour!

In her 1859 book "Notes on Nursing," Florence Nightingale railed against unnecessary noise, calling it "the most cruel absence of care."

Noise Mitigation or Abatement It's a Constant Concern

Architectural solutions

Main article: Architectural acoustics

Beyond the interior acoustics cited above under aircraft noise, there has been a steady trend to design quieter buildings with regard to sources within and without the structure itself.^{[citation needed]} In the case of construction of new (or remodeled) apartments, condominiums, hospitals and hotels, many states and cities have stringent building codes with requirements of acoustical analysis, in order to protect building occupants. With regard to exterior noise, the codes usually require measurement of the exterior acoustic environment in order to determine the performance standard required for exterior building skin design. The architect can work with the acoustical scientist to arrive at the best cost-effective means of creating a quiet interior (normally 45 dBA). The most important elements of design of the building skin are usually: glazing (glass thickness, double pane design etc.), roof material, caulking standards, chimney baffles, exterior door design, mail slots, attic ventilation ports and mounting of through the wall air conditioners.
Regarding sound generated inside the building, there are two principal types of transmission. Firstly, airborne sound travels through walls or floor and ceiling assemblies and can emanate from either human activities in adjacent living spaces or from mechanical noise within the building systems. Human activities might include voice, amplified sound systems or animal noise. Mechanical systems are elevator systems, boilers, refrigeration or air conditioning systems, generators and trash compactors. Since many of these sounds are inherently loud, the principal design element is to require the wall or ceiling assembly to meet certain performance standards^[7] (typically Sound transmission class of 50), which allows considerable attenuation of the sound level reaching occupants.
The second type of interior sound is called Impact Insulation Class (IIC) transmission. This effect arises not from airborne transmission, but rather from transmission of sound through the building itself. The most common perception of IIC noise is from footfall of occupants in living spaces above. This type of noise is more difficult to abate, but consideration must be given to isolating the floor assembly above or hanging the lower ceiling on resilient channel.
Both of the above transmission effects may emanate either from building occupants or from building mechanical systems such as elevators, plumbing systems or heating, ventilating and air conditioning units. In some cases it is merely necessary to specify the best available quieting technology in selecting such building hardware. In other cases shock mounting of systems to control vibration may be in order. In the case of plumbing systems there are specific protocols developed, especially for water supply lines, to create isolation clamping of pipes within building walls. In the case of central air systems, it is important to baffle any ducts that could transmit sound between different building areas.
Designing special purpose rooms has more exotic challenges, since these rooms may have requirements for unusual features such as concert performance, sound studio recording, lecture halls. In these cases reverberation and reflection must be analyzed in order to not only quiet the rooms but prevent echo effects from occurring. In these situations special sound baffles and sound absorptive lining materials may be specified to dampen unwanted effects.

Noise Polllution Another Man-made Problem and Only Getting Worse

noise pollution

noise pollution, human-created noise harmful to health or welfare. Transportation vehicles are the worst offenders, with aircraft, railroad stock, trucks, buses, automobiles, and motorcycles all producing excessive noise. Construction equipment, e.g., jackhammers and bulldozers, also produce substantial noise pollution.

Noise intensity is measured in decibel units. The decibel scale is logarithmic; each 10-decibel increase represents a tenfold increase in noise intensity. Human perception of loudness also conforms to a logarithmic scale; a 10-decibel increase is perceived as roughly a doubling of loudness. Thus, 30 decibels is 10 times more intense than 20 decibels and sounds twice as loud; 40 decibels is 100 times more intense than 20 and sounds 4 times as loud; 80 decibels is 1 million times more intense than 20 and sounds 64 times as loud. Distance diminishes the effective decibel level reaching the ear. Thus, moderate auto traffic at a distance of 100 ft (30 m) rates about 50 decibels. To a driver with a car window open or a pedestrian on the sidewalk, the same traffic rates about 70 decibels; that is, it sounds 4 times louder. At a distance of 2,000 ft (600 m), the noise of a jet takeoff reaches about 110 decibels—approximately the same as an automobile horn only 3 ft (1 m) away.

Subjected to 45 decibels of noise, the average person cannot sleep. At 120 decibels the ear registers pain, but hearing damage begins at a much lower level, about 85 decibels. The duration of the exposure is also important. There is evidence that among young Americans hearing sensitivity is decreasing year by year because of exposure to noise, including excessively amplified music. Apart from hearing loss, such noise can cause lack of sleep, irritability, heartburn, indigestion, ulcers, high blood pressure, and possibly heart disease. One burst of noise, as from a passing truck, is known to alter endocrine, neurological, and cardiovascular functions in many individuals; prolonged or frequent exposure to such noise tends to make the physiological disturbances chronic. In addition, noise-induced stress creates severe tension in daily living and contributes to mental illness.

Noise is recognized as a controllable pollutant that can yield to abatement technology. In the United States the Noise Control Act of 1972 empowered the Environmental Protection Agency to determine the limits of noise required to protect public health and welfare; to set noise emission standards for major sources of noise in the environment, including transportation equipment and facilities, construction equipment, and electrical machinery; and to recommend regulations for controlling aircraft noise and sonic booms. Also in the 1970s, the Occupational Safety and Health Administration began to try to reduce workplace noise. Funding for these efforts and similar local efforts was severely cut in the early 1980s, and enforcement became negligible.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved.

Read more: noise pollution — Infoplease.com http://www.infoplease.com/ce6/sci/A0835810.html#ixzz1oMyBMgZu

A Brief Histroy of Resilient Channel

History of Resilient Channel:

Resilient Channel was originally brought to the mass market decades ago by USG (United States Gypsum). The product was trademarked as RC-1, and tested extensively at Riverbank Acoustic Laboratories. Today many installers, architects and material retailers refer to any channel with one “leg” as RC-1. It’s important to note that USG hasn’t dealt with the original resilient channel design for years and years. Since then, many manufacturers have made a “resilient channel” and informally referred to previous USG test data for acoustic performance. This is entirely misleading and quite unfortunate. Resilient channel available today has many profiles, mil thicknesses and performance characteristics, so it really not possible to simply predict how any given piece of “resilient channel” will perform. Additionally any 1 or 2 legged resilient channel is not specified by the Steel Stud Manufacturers Association (SSMA). So there are no standards for its construction or use.

How Acoustic Barriers Reduce Sound

Anyone who's ever shared a wall with someone else has probably wondered if the walls were intentionally thin, or the neighbors intentionally loud. Often the assumption is that the walls between dwellings simply need to be thicker to muffle sound. The fact is that the design of the wall, not the size, can be a contributing factor in transmitting sound from one side to the other.

Consider how walls are constructed in most multi-family housing units. Basically, they are made of gypsum board firmly attached to both sides of a wood frame. When sound waves hit one side of the wall it causes the gypsum board on that side to vibrate. Since the gypsum board is rigidly connected to the frame, the vibration is transmitted right through the framing to the gypsum board on the other side. Those same vibrations travelling through the wall frame can also send sound throughout adjacent floors and ceilings. Noises will radiate through the structure because there's almost nothing there to cushion or absorb the sound waves.

In order to significantly dampen those approaching sound waves, United Plastics Corporation’s dB-3 Pro can be installed between one of the gypsum walls and the frame. The United Plastics Corporation dB-3 Pro, which is made of 100% post-industrial materials  acts as a shock absorber in this system, muffling vibrations coming from either side of the wall. United Plastics Corporation’s dB-3 Pro is an improvement over the resilient channel system’s that are routinely used to improve the sound ratings for walls and are especially effective in floor/ceiling constructions.

Resilient channels typically add 3 to 5 Sound Transmission Class (STC) points to an otherwise identical wall or ceiling, whereas United Plastics Corporation’s dB-3 Pro up’s the ante by adding between 3-5 Sound Transmissions Class (STC) points per layer. This can most often is more than enough to meet the STC and Impact Insulation Class (IIC) ratings required by the project design goals or local codes. In California, the building code specifies minimum lab tested ratings of STC 50 and IIC 50 for partitions in multi-family dwellings.

In fact, the IIC 50 rating required by the building code is easily achieve using the dB-3 Pro wall material when hung in the ceiling in a multi-family project. Unless the floors are completely carpeted (which is rare for kitchens and bathrooms), it is very difficult to achieve IIC 50 ratings without using resilient channels and batt insulation in the floor-ceiling construction

Just what is the difference between Structure-borne and Air-borne noise?

	The noise given off by a particular source can usually be categorised into one of the following forms: Structure-borne noiseThis is the sound generated from a vibrating source or impact event. The acoustic energy created by these vibrations is transmitted into the structure of a building (e.g. floors, walls, pipe-work etc,) or into mechanical elements (e.g. metal frames, panel work, supports etc.) This energy travels through solid structures and is released as air-borne noise at different locations within the building or mechanical system. Air-borne noise This is the sound that travels through the air and into the surrounding environment. In closed environments such as rooms and enclosures, air-borne sound may reverberate and increase the levels of noise both in and outside the contained space. Most forms of noise will contain contributions from both air-borne and structure-borne sound. Although measures can be taken to limit structure-borne components, such as by isolation and damping, air-borne sound can be treated with the use of absorbing materials. ArmaSound RD has an extremely high absorption performance per unit thickness, offering a solution for the most demanding applications.
	By way of example, someone who is hammering a nail into a wall (See diagram) will create structural noise, causing vibration of the surrounding structure. However, they will create a significant amount of air-borne noise, which will be clearly heard in the room where the action is taking place. As the noise travels, it may also change forms. I.e. Structure-borne noise may eventually cause sympathetic vibrations in other structures and release airborne sound. In this example, the structure borne components of the noise may travel towards the light fitting that’s in the same room causing it to shake and release audible clatter. Airborne noise may also change into structure-borne and back to air-borne. This process is often called ‘transmission’ of sound energy. Once again, in the example above, the air-borne components of the noise may travel into the far wall, and then out through the other side and into an adjoining room.