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An international IEEE standard for WLAN networks, operating at 2.4 GHz and providing 11 Mbps (where IEEE stands for Institute of Electrical and Electronics Engineers, Inc.).


In acoustics, the energy of sound waves being taken in (entering) the surface of any material rather than being bounced off or reflected. Materials are rated in terms of their ability to absorb sounds.

Access Hook

Used in concealed tee system to support the last row of tile to be installed in a 4'x4' module that also allows access to the plenum above. Also called Saddle Spline.

Access Point (AP)

A transceiver or radio component in a wireless LAN that acts as the transfer point between wired and wireless signal, and vice versa. The AP is connected to antennas as well as to the wired LAN system.

Access Tile

A removable acoustical tile, with special kerfing details.

Acoustical Materials

Materials which have absorption coefficients.

American National Standards Institute (ANSI)

An independent organization of trade associations, technical societies, professional groups and consumer organizations formerly know as the United States of America Standards Institute (USASI or ASI), and previously as the American Standards Association (ASA).

American Society for Testing Materials

A nonprofit organization that establishes standard tests and specifications for construction materials such tests, and specifications usually are referred to by the abbreviation ASTM followed by a numerical designation.


The maximum variation of any wave from its mean value. Increasing any sound wave's amplitude increases its loudness.


A wireless system component that converts wired electrical energy to wireless radio waves, and directs them through the air in some pattern.

Articulation Class (AC)

Rates the listener's ability to understand the spoken work within a space, expressed as a decimal with 1.0 being perfectly understandable. The privacy index is derived from the A1 calculation. Lower A1 ratings (less than 0.2) indicate that adjacent spoken words are less intelligible, therefore less distracting. The sum of the weighted sound attenuations in a series of 15 test bands. Note: AC has replaced Noise Isolation Class (NIC) as the accepted industry standard performance value. NIC is based on hearing sensitivity rather than discernment of actual speech, which is the primary concern in open office layouts prevalent in acoustical design work. Verify the rating methodolgy with manufacturer's published data.

Articulation Index (AI)

Measure of speech intelligibility in a room. A numerical value ranging from 0 to 1. In an open-plan office, an AI of 0.1 is low, indicating that little, if any, of a conversation will be intelligible on the other side of a screen. An AI of 0.6 would make for poor speech privacy.

ASTM A 641

Standard specification for zinc-coated (galvanized) carbon steel wire (hanger wire).

ASTM A 653

Standard specification for steel sheet, zinc-coated (galvanized), or zinc-iron alloy coated by the hot dip process.

ASTM B 117

Environmental performance test method.

ASTM C 208

Standard specification for insulating board (cellulosic fiber), structural and decorative.

ASTM C 209

Standard methods of testing insulating board (cellulosic fiber), structural and decorative.

ASTM C 367

Test methods for strength properties of prefabricated architectural acoustical tile or lay-in ceiling panels.

ASTM C 423

Standard test method for sound absorption and sound absorption coefficients by the reverberation room method.

ASTM C 518

Standard test method for steady-state heat flux measurements and thermal transmission properties by means of the heat flow meter apparatus.

ASTM C 522

Test method for airflow resistance of acoustical materials.

ASTM C 635

Standard specification for metal suspension systems for acoustical tile and lay-in ceilings.

ASTM C 636

Standard practice for installation of metal ceiling suspension systems for acoustical tile and lay-in panel.

ASTM C 645

Standard specification for drywall furring products.

ASTM D 3273

Standard test method for resistance to growth of mold on the surface of interior coatings in an environmental chamber.

ASTM E 119

Standard methods of fire tests of building construction and material (hourly fire resistance rating test for an entire assembly).

ASTM E 1264

Standard for the classification of acoustical ceiling products.

ASTM E 136

Standard test method for behavior of materials in a vertical tube furnace (combustibility test method) (often used for Coast Guard applications).

ASTM E 1414

Standard test method for airborne sound attenuation between rooms sharing a common ceiling plenum (previously known as ASTM E 413).

ASTM E 1477

Standard test method for luminous reflectance factor of acoustical material by use of integrating-sphere reflectometers (previously known as ASTM C 523).

ASTM E 176

Standard terminology relating to fire standards.

ASTM E 336

Standard test method for measurement of airborne sound insulation in buildings.

ASTM E 580

Standard practice for application of ceiling suspension systems for acoustical tile and lay-in panels in areas requiring seismic restraint.

ASTM E 795

Standard practices for mounting specimens during sound absorption tests.


Test method for surface burning characteristics of building materials (25-foot tunnel test for smoke and flame spread on an individual product, not an assembly).


Method for laboratory measurement of airborne sound transmission loss of building partitions.


Standard method for testing of water vapor transmission.


Abbreviation for American Society for Testing Materials.


In acoustics, the diluting or holding back of the energy of sound waves as they pass through a material. Materials are rated for their ability to prevent sounds from traveling through them.

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Backloaded Insulation

Thermal/acoustical insulation placed above the ceiling suspension system, laid across the horizontal grid members above the acoustical panels or tile. Also referred to as "backloading."


The bandwidth of an antenna is the range of radio frequencies it can transmit or receive efficiently. The bandwidth of the communication device, such as an access point, is the range of frequencies used by or allocated to the communication device. Bandwidth is sometimes also used to describe the throughput of an information network. Networks with higher data rates have higher throughput and may be said to have more bandwidth. Higher information content typically demands more bandwidth.

Bevel Edge

An acoustical tile is considered bevel edge material when the face of the tile turns up at the edge at approximately 45 degrees for 1/8" to 1/4" around the perimeter of the tile.


Added feature of HumiGuard™ Plus ceilings; a fungicide treatment to inhibit or retard growth of mold or mildew on products' painted surfaces.


A Special Interest Group, comprised of leaders in the telecommunications, computing, and network industries, that is developing a new standard for short range wireless communications between devices, such as between PDAs and laptop computers or between mobile phones and vending machines. Bluetooth uses the same frequency band (2.4 GHz) as 802.11b wireless networks.


Building Officials and Code Administrators - Publishes the National Building Code every three years, with yearly supplements. Most commonly referred to in the northeast United States.

Border Cut

Cut made on both ceiling panel and grid at the perimeter of the installation.

Breather Spline

Spline used to link tiles in a concealed tee installation and to prevent air infiltration.


The upper ridge of the runner or cross tee with a rectangular, triangular or round configuration. Adds structural load strength to the component.

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The rolled covering on the flange of a T-Bar. T-Bars come with an aluminum or steel cap and in many colors.

Ceiling Attenuation Class (CAC)

Rates a ceiling's efficiency as a barrier to airborne sound transmission between adjacent closed offices. Shown as a minimum value, previously expressed as CSTC (Ceiling Sound Transmission Class). A single-figure rating derived from the normalized ceiling attenuation values in accordance with classification ASTM E 413, except that the resultant rating shall be designated ceiling attenuation class. (Defined in ASTM E 1414.) An acoustical unit with a high CAC may have a low NRC.

Ceiling Sound Transmission

In a suspended ceiling construction, the transmission of sound between adjoining rooms by way of the path consisting of the ceiling of each room and the continuous plenum over, and common to, both rooms.

Ceiling Suspension System

A system of metal members designed to support a suspended ceiling, typically an acoustical ceiling. Also may be designed to accommodate lighting fixtures or air diffusers.


Refers to frequencies in the 800 MHz band in which some mobile phones operate.


Ceiling Interior Systems Construction Association (guide for basic installation of ceiling products).

Clean Room

An assembly room for precision products whose quality would be affected by dust, lint or airborne pathogens; usually has smooth room surfaces to prevent dust collection; air precipitators or filters keep dust, lint, etc. to a specified minimum level.


Several clip designs are available to suit applications such as fire resistance, wind uplift and impact. Fire-resistance rated designs have exact requirements, including the mandatory use of hold-down clips for acoustical panels or tiles weighing less than 4.9 kg/m2 (1.0 pound per square foot). For rooms with significant air pressure differential from adjacent spaces, retention clips may be necessary to retain panels in place. Maintaining air pressure values may also require perimeter panel seals, typically a closed cell foam gasket with adhesive on one side.

Concealed Mounting System

Tile suspension system using T-Bars and splines, which fit into kerfs cut into tile edges. Unlike exposed-grid systems, concealed mounting systems are not visible from below the ceiling, inverted tee, "H and T", "Z" profile grids are common for these applications with provisions for full plenum access usually incorporated into the grid design.

Cross Runner

The secondary or cross beams of a mechanical ceiling suspension system, usually supporting only the acoustical tile. In some suspension systems, however, the cross runners also provide support for lighting fixtures, air diffusers, and other cross runners.

Cross Tee

Tee that is inserted into the main runner to form different module sizes.

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Data Transmission Rates

The speed at which data is transferred over a communications line measured in bits per second.

DBA (A-weighted decibel)

A single-number measurement based on the decibel but weighted to approximate the response of the human ear with respect to frequencies.

Decibel (dB)

A unit to express differences in power. In acoustics, equal to ten times the logarithm of the ratio of one sound and lower-intensity reference sound. One decibel indicates a difference of about 26% and is about the smallest change the ear can detect. The dB level is a logarithm quantity; the maximum normal level is approximately 120dB


Bending or deviation from a stratight line or course. Used here as the standard by which allowable load for suspension system components is measured.

Demountable Partition, Relocatable Partition

A nonload-bearing partition of dry construction, assembled from prefabricated components which can be installed, removed, and then reinstalled at a different location; may be full height from floor to ceiling, or partial height.

Distributed Antenna System (DAS)

A network of components that input a radio frequency (wireless) signal, convert it to wired media, transport it throughout a facility, and then re-convert it back to a wireless signal. A DAS is used to bring radio frequency coverage inside a facility for mobile users.


The technique of using more than one antenna to ensure that the received signal strength is always maximized.

Double Web

Indicates two-layers of material in the construction of the vertical web of main runners and cross tees.

Downward Access System

Direct access is achieved by removing individual units with an access clip or key. Multiple panels designed as end- or side-pivoting units can also be used. The number of permissible access openings are fewer with an end-pivot design. Downward access may be desirable if tight plenum clearance is a problem. In fire-rated designs, the amount of each access area and pan size is governed by testing criteria.

Dual Band

Refers to an antenna, communication device, or other RF hardware that works at two different frequencies (or bands).

Duty Classification

Load carrying capability of grid components in pounds per linear foot (Light: 5 lbs., Intermediate: 12 lbs., Heavy: 16 lbs.).

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A plating process that deposits a coating of zinc on a cold rolled steel substrate. Thickness or weight of coating can be varied and is typically categorized as heavy-electro through standard-electro or "flash" electrogalvanized. Process providing rust resistance for metal.

Environmental Systems

Grid systems that are made of base materials that withstand a variety of moist and corrosive conditions.

Expansion Joint

Area of a fire-rated component designed and punched to provide thermal expansion relief for that component. Due to expansion of steel when heated, this expansion control is necessary to keep the fire membrane intact.

Exposed Grid System

Structural suspension system for lay-in ceiling panels. Factory-painted supporting members are exposed to view. Exposed tee surfaces may be continuous or have an integral reveal. Reveals are typically formed as channel profiles extending down from the tee leg. Bolt-slot type reveal designs can accommodate partition attachment. The choice may be restricted by appropriate tee width for panel selected and limitations on available panel edge details for the chosen grid profile.

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Fiberglass Panels

Processed from a molten state into fibrous glass strands, then formed into board stock. The manufacturing process requires a separate dimensionally stable facing material laminated to the fiberglass core to provide texture and pattern. Fiberglass, vinyl and polyester facing are typically used.

Fire Guard Grid

Fire resistance rated grid.

Fire Rated

Refers to the UL fire resistance rating of an assembly.

Fire Resistance

The property of acting as a barrier to fire. Acoustical ceiling systems form a membrane to contain fire within a room. Fire-rated assemblies (including ceiling panels, suspension system, light fixtures and diffusers, and structural components) are given ratings of one, two, three, or four hours as tested per ASTM E 119.


Method of imparting a set of ragged depressions into the face of acoustical tile or panels during manufacture for appearance and acoustical performance.

Fixture Weight

Individual weight of mechanical services supported by ceiling grid members.

Flame Spread Index

A numerical designation, applied to a building material, which is a comparative measure of the ability of the material to resist flaming combustion over its surface the rate of flame travel, as measured under the applicable ASTM E 84 test, in which a selected species of untreated lumber has a designated value of 100, and noncombustible inorganic reinforced cement board has a value of 0.

Flame Spread Rating

A single number measurement of the flame spread across the surface of a material. Defined by ASTM E 84 commonly known as the 25-foot tunnel test, the number is obtained by comparing with red oak flooring. The following classes are defined under ASTM E 1264:

Flame Spread Rating Smoke Rating ASTM E 1264 Class
0-25 0-50 A
26-75 - B
76-200 - C


Horizontal surface on the face of the tee, visible from below the ceiling. The part of the grid to which the color cap is applied. Most grid system flanges are either 15/16" or 9/16".

Flanking Sound Path

A sound transmission path, such as a structural path, that bypasses a transmission barrier.


The average illumination resulting when one lumen of light falls on one square foot of surface. Total lumens on surface divided by area of surface equals footcandles.


1 a: Cycles per unit of time. b: The number of times an electromagnetic wave goes through a complete cycle in one second, measured in Hertz (Hz) : the frequencies of audiblespeech lie in the range of 400-2000 Hz.

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The increase in signal strength. For antennas, the gain is a comparative number based on an ideal antenna. For a given power level, higher gain typically indicates more directional radiation pattern.


A generic term used to describe a sheet or coil of steel coated with zinc applied in an electrogalvanizing or dipping process.

Gasket Grid

Ceiling suspension system that has foam rubber gasketing attached to the topside of the flanges. Used in clean room ceilings to seal the panels to the grid.


Thickness of the steel used to make a grid member. May be expressed by a number designation (26 GA.) or in thousandths of an inch (0.013).


Structural system of main beams, cross tees, and associated hardware which hangs from the deck above and supports lay-in, concealed or surface attached ceiling panels.

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Hanger Wires

Wire employed to suspend the acoustical ceiling from the existing structure. The standard material is 2.05 mm (12 guage) galvanized, soft annealed steel wire, conforming to ASTM A 641M or A 641. Heavier guage wire is available for higher load carrying installations or situations where hanger wire spacing exceeds 1200 mm (4 feet) on center. Stainless steel wire and nickel-coppper alloy wire are frequently used in severe environment designs. Seismic designs or exterior installations subject to wind uplift may require supplemental bracing or substantial hanger devices such as metal straps, rods, or structural angles.

Heavy-Duty Systems

Primarily used for commercial structures in which the quantities and weights of ceiling fixtures (lights, air diffusers, etc.) are greater than those for an ordinary commercial structure.

Hertz (Hz)

One cycle per second.

Hold Down Clip

Mechanical fastener that snaps over the bulb of a grid system to hold ceiling panels in place.

Hook Tee

Cross tee with an end tab that hooks through the rout hole and rests on the vertical web of the main runner.

Hot Dipped Galvanized

Process to coat steel to offer environmental resistance to corrosion. Cold rolled steel is submerged (dipped) into a molten zinc bath. A heavy coating of zinc is applied to the steel substrate. Zinc coating thickness varies and is designated by a "G" series, such as G-60 or G-90.

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Organization based in Sacramento, California, that sets seismic standards primarily for western United States. Publishes the Uniform Building Code.

Illuminance Levels

Illuminance is the quantity of light falling onto a surface. It is measured in foot candles or lux (metric measure). One foot candle is approximately 10 lux.

Impact Resistance

In certain applications, such as gymnasiums, locker rooms, classrooms, corridors, and institutional settings, acoustical ceiling assemblies may be subjected to impact from objects. Impact resistance assemblies with acoustical lay-in panels typically require retention clips to keep panels in place upon direct impact.

Integral Splice

Connects the mains or tees together and is formed from the base metal of the components.

Intermediate-Duty Systems

These are used primarily for ordinary commercial structures where some ceiling loads, due to light fixtures and air diffusers, are anticipated.

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Kerfed two sides, cut two sides.


Kerfed and cut on all four sides.


Groove in the edge of ceiling tile, which accommodates and hides a suspension member.

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L/360, Span/360

The distance between support points of a suspension system member divided by 360. The result of this mathematical equation is the maximum amount of deflection that is allowed under ASTM C 636.


Local Area Network. Also referred to as Ethernet. See also: PAN, WAN, WLAN.

Light Loss Factor (LLF)

Used to calculate illuminance loss after a given period of time and under given conditions, like dirt accumulation and heat buildup in the fixture.

Light Reflectance (LR)

Light reflectance of a surface is its property or reflecting light. The measure of light reflectance is that fraction of the specified incident light, which is reflected by the surface. (Defined in ASTM E 1477).

Light-Duty Systems

Used primarily for residential and light commercial structures where ceiling loads other than acoustical tile or lay-in panels are not anticipated.


Amount of force (weight) that is applied to a lineal foot of any load of any load-bearing member of a ceiling system.

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Main Beam, Main Runner, Main Tee

Primary or main beams of the type of ceiling suspension system in which the structural members are mechanically locked together. Provide direct support for cross runners and may support lighting fixtures and air diffusers, as well as the acoustical tile. Supported by hanger wires attached directly to the existing structure or installed perpendicular to carrying channels and supported by specially designed sheet metal or wire clips attached to the carrying channels. Typically a 12' piece located 4' on center. Also referred to as "H" runners and "Z" bars.


Million (Mega) bits per second.

Mineral Wood

A man-made wool-like material of fine inorganic fibers made from slag, used as loose fill or formed into blanket, batt, clock, board, or slab shapes for thermal and acoustical insulation.


Cross tee end detail is a "hook" insertion contrasted with the XL that is "stab" insertion. The ML end detail is quick and easy to install; however, it does not meet most seismic requirements greater than Zone 2.

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Noise Isolation Class (NIC)

A single-number rating of the sound-isolating performance of a building element. Used in place of when flanking sound paths cannot be isolated to establish the Field Sound Transmission Class (FSTC).

Noise Isolation Class Prime (NICP)

A single-number rating of the acoustical performance of any screen-ceiling combination. It is a measure of speech privacy, with higher numbers indicating greater privacy. Determined by plotting the functional interzone attenuation of the screen-ceiling combination against frequency.

Noise Reduction Coefficient (NRC)

Average sound absorption coefficient measured at four frequencies: 250, 500, 1,000 and 2,000 Hz expressed to the nearest integral multiple of 0.05. Rates of ability of a ceiling or wall panel or other construction to absorb sound. NRC is the fraction of sound energy, averaged over all angles of direction and from low to high sound frequencies that is absorbed and not reflected.

Nonspecular Surface

Describes a surface which is diffuse. Meaning it reflects light in equal amounts in all directions. This is important because a non-specular ceiling's brightness will be the same regardless of viewing position. Typically, nonspecular (diffuse) surfaces are less glossy and produce less offensive flare.

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Open Plan Office

An office in which acoustical screens, most commonly 60-inches high, are used in place of ceiling-high partitions. Ceilings used in open plan offices must have different acoustical properties than those used in closed offices.


Offset on the end of some cross tees that rests on top of the supporting member's flange. Increases stability and moves cut edge of tee out of the visible plane of the ceiling.

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Personal Area Network. Term often used in reference to Bluetooth technologies under development that will enable short-range communications among wireless devices.


Any lay-in acoustical board that is designed for use with an exposed mounting system.


A dividing wall within a building; may be load-bearing or nonload-bearing. In sound transmission considerations, any building component (or a combination of components), such as wall, door, window, roof or floor-ceiling assembly, that separates one space from another.

Perimeter Trim

Components of right angle shape, either simple or compound (stepped) bends, set at the suspension grid perimeter, flush to the abutting vertical surface.


Refers to "Personal Communication Systems" and to specific frequencies in the 1900 MHz band at which some mobile phones operate

Pin Perforation

A method of improving the acoustical performance of a ceiling tile or panel by punching holes in its surface during manufacture.


In suspended ceiling construction, the space between the suspended ceiling and the main structure above.

Plenum Barrier

Vertical surface framed from the structure above the finished ceiling and sealed to prevent the passage of air or sound.


The orientation of the electromagnetic waves; can be linear (vertical or horizontal) and circular.

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R Factor

A number measuring a material's resistance to heat flow. R stands for resistance, the inverse of conductivity. Values reported on this website were determined by the ASTM C 518 test method. Values are reported at a mean temperature of 75 degrees Fahrenheit (24 degrees Celsius), and as the inverse of BTU/hr-sf-*F (Imperial units), and Watts/m2-*C (metric units).

Radio Frequency(RF)

The area (or band) of the electromagnetic spectrum where most radio communication takes place, typically from 100 KHz to 100 GHz


A base station set up to extend the range of mobile communication by "repeating" everything it hears on its receiver frequency over its transmit frequency. For an in-building wireless system, a repeater generally consists of an external, high-gain antenna combined with a bi-directional signal amplifier. This repeater is then connected to a DAS.


Persistance of reflected sound in a room after its source has stopped emitting sound.

Reverberation Time

Time required for a sound to decay to a value one millionth of its original intensity or to drop 60 decibels.

Rotary Stitching

Process by which two vertical layers of steel are stitched or bonded together to form more homogeneous component exhibiting increased column strength, torsional strength, and overall handleability. Armstrong is the only grid manufacturer to employ this technology.

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Process of cutting grooves into the face of acoustical panels creating a different geometric visual with decorative and some acoustical benefit. Scoring often mimics the suspension grid, camouflaging it and making 2' x 2' panels look like 12" x 12" tile.


For applications where cleanliness is a priority, acoustical units may require cleaning beyond normal maintenance procedures. Acoustical panels with special facing materials such as Mylar or vinyl film offer superior scrubbability without compromising panel finish integrity. Metal ceilings may also be used for scrubbable applications. The accepted test procedure is the Gardner Scrubbability Test ASTM D 2486.

Seismic Compression/Tension

The capability of a grid member connection to carry a mean ultimate test load in compression/tension.

Seismic Load

The force produced on a structural mass owing to its acceleration, induced by an earthquake.

Semi-Concealed Installation System

Installation system in which tile kerfs are shallow enough to leave gaps between the tiles in one direction, exposing the grid on two sides. Usually an inverted grid. Two opposing panel edges are fabricated for a concealed grid profile.

Service Provider

Also referred to as wireless operators or "carriers," Service Providers sell minutes of use (MOU) on their wireless networks.

Shadow Molding

A W-shaped molding that will produce a reveal or space between the ceiling and the wall when fastened to the wall.

Site Survey

A comprehensive facility study, typically performed by a radio frequency engineer, employed by a systems integrator. The goal of the site survey is to create an accurate wireless system design/layout and budgetary quote.

Slotted Systems

Either bolt-slot or screw-slot systems, both of which offer a dimensional look to an otherwise flush ceiling using 9/16" exposed components. Typically feature a 1/8" or 1/4" groove that runs down the center of the components.

Smoke Developed

The ratio of the smoke emitted by a burning material to the smoke emitted by the red oak standard material.

Smoke Developed Rating

A relative numerical classification of a building material as determined by an ASTM E 84 test of its surface burning characteristics.

Sound Attenuation

The reduction in the intensity or in the sound pressure level of sound, which is transmitted from one point to another.

Sound Leaks

Cracks under doors, openings in a wall pipe or wiring holes, etc., which allow sound to escape through a structure from one room to another.

Sound Transmission Class (STC)

A single-number rating of a structure's efficiency as a barrier to airborne sound at 16 speech frequencies from 125 to 4000 Hz. (See ASTM procedure E 1414 for rating method.) Rates the ability of a wall or other construction to block sound: STC is a decibel measure of the difference between the sound energy striking the panel or construction on one side and the sound energy transmitted from the other side. This includes sound from all angles of direction, and from low and high sound frequencies.

Sound Transmission Loss

The amount of sound lost as the sound travels through a material. Acoustical ceiling assemblies are rated in terms of Sound Transmission Classifications. An STC value of 20-25 would indicate that even low speech would be audible in an adjoining room. An STC value of 50-60, on the other hand, would indicate that loud sound would be heard only faintly or not at all.

Special Environments

Clean rooms, meat processing plants, and kitchens are examples of special environments. United States Department of Agriculture (USDA), Food and Drug Administration (FDA), or other federal, state, or municipal regulations may apply in these situations. For example, USDA acceptance is mandatory where ceiling assemblies are installed in meat or poultry processing areas to ensure that ceiling components do not contain any prohibited chemicals that will contaminate meat or poultry, and ceiling components must be cleanable and able to resist abuse. FDA approval covers food handling areas such as commercial or school kitchens and also requires limitations on, or exclusion of certain chemicals in ceiling components.

Speech Range Absorption

The average of the absorption coefficients at 500, 1000, 2000, and 4000 Hertz.


A strip of metal or fiber inserted in the kerfs of adjacent acoustical tile to form a concealed mechanical joint seal.

Square Edge

Edge design for acoustical panels which, when viewed in profile, forms a rectangle. Though they are the simplest and least expensive to manufacture, square-cut acoustical panels do the least to hide the suspension grid.

Stab End Detail

Designed to be inserted with a forward motion.

Stabilizer Bar

U-shaped channel, either 24' long or 48' long, designed to maintain cross tee spacing at the perimeter. Used in seismic installations to help prevent cross tees and panels from falling from the suspension system during an earthquake.

Stiffening Brace

Used to prevent uplift of grid caused by wind pressure in exterior applications.


Dimples impressed in grid members to knit the webs together. (See rotary stitching.)

Surface Burning Characteristics

Published flame spread and smoke developed indices for acoustical units measure surface burning behavior (characteristics) during exposure to fire. Test methods provide data in comparison with noncombustible cement board and untreated red oak lumber when exposed to fire under similar conditions. Nationally accepted equivalent test methods are ASTM E 84, NFPA 255, and UL 723.

Suspension System

A metal grid suspended from hanger rods or wires, consisting of main beams and cross tees, clips, splines and other hardware which supports lay-in acoustical panels or tiles. The completed ceiling forms a barrier to sound, heat, and fire. It also absorbs in-room sound and hides ductwork and wiring in the plenum.

System Integrator

System integrators provide engineering design, layout, and installation of wireless systems. System Integrators may often be authorized resellers of various system hardware providers (see "System Provider").

System Provider

A system provider manufactures and sells components of or a complete wireless system. Their customers are system integrators or service providers.

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Any metal member of "T" cross section used in ceiling suspension systems.


A functional edge detail. Tegular suspended ceiling panels have a rabbeted/reveal edge design that allows them to extend below the supporting grid, making the grid less conspicuous.

Temperature and Relative Humidity (RH) Resistance

Temperature and humidity affect acoustical panel and tile dimensional and planar stability. Standard acoustical panels and tiles are designed for installation within the normal occupancy condition range of 15 to 29 degrees Celsius (60-85 degrees Farenheit) and maximum 70 percent RH. When the in-service use temperature and RH are expected to exceed these ranges, consider the use of acoustical units specifically designed for these applications, like HumiGuard ceilings. Anticipate lower overlaid thermal/acoustic insulation (commonly referred to as "backloading") limits for these designs.

Thermal Resistance

Where thermal resistance is required for an acoustical ceiling assembly, provide adequate ventilation to avoid high humidity conditions in the ceiling plenum that could damage assembly components. Thermal insulation above the ceiling plane may place the dew point within the ceiling plenum, increasing the potential for damage to ceiling components due to condensation. When in doubt, consult a professional engineer for venting recommendations. Note: Thermal insulation overlaid on the back of suspended ceilings may cause panel deflection and limit access to the ceiling plenum. Verify limitations with manufacturer. Caution: Most tested fire-resistance-rated acoustical ceiling assemblies prohibit the use of overlaid insulation. Adding this component runs the risk of voiding acceptability of the tested assembly.


Acoustical ceiling board, usually 12" x 12", which is stapled, cemented, or suspended by a concealed grid system. Edges are often kerfed and cut back.

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UBC 25-2

Uniform Building Code (seismic standard)

UL 580

Wind uplift test (Class 15 = 15/lbx./sf; Class 90 = 90/lbs./sf.).

UL Label

An identification affixed to a building material or component, with the authorization of Underwriters' Laboratories, Inc., indicating that the labeled product: (a) has a rating based on the performance tests of such products; (b) is from a production lot found by examination to be made from materials and by processes essentially identical to those of representative products which have been subjected to appropriate fire, electrical hazard, or other tests for safety; and (c) is subject to the reexamination service of UL.


Underwriters' Laboratories, Inc.

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Wide Area Network


For applications where cleanliness is important, acoustical units may require cleaning beyond normal maintenance procedures. Acoustical panels with special surfaces such as DUNE, ULTIMA, OPTIMA, and VPO coatings offer superior wash resistance without compromising panel finsih integrity. The accepted test procedure is the Gardner Washability Test ASTM D 4213.

Wind Uplift

Resistance to wind uplift forces may be necessary for exterior ceiling and soffit designs. A substantial hanger system design, incorporating rods or straps, plus acoustical unit retention clips, is commonly required. Verify code requirements for wind uplift force resistance and manufacturer's recommendations for ceiling installations based on these values.


Wireless Local Area Network

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Z-Bar Concealed

Metal strips which are attached to a 1-1/2" carrying channel, one foot on center and at right angles to the channel. Also called Zee runners.

Z-Bar Exposed

A Z-Bar clipped to 1-1/2" channels to support acoustical tile on the exposed bottom painted flange of the "Z."

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