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Any material that absorbs at least 50% of the sound energy that strikes it. The NRC is a measure of a sound absorber performance.


Property of a material or object to convert sound energy into heat rather than reflecting the sound energy.

Access Hook

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

Access Tile

A removable acoustical tile with special kerfing details.

Acoustical Material

Any material that affects the sound level or direction of travel of a sound wave.

Ambient Noise

The lowest background noise level in a space comprised of sound from sources near and far.

American National Standards Institute (ANSI)

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

American Society for Testing and Materials (ASTM)

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.


An electronic component that is used in sound system applications to increase the power of a low level Source Signal (microphone, CD player, etc.) into a high power Output Signal to drive the loudspeakers.


Variation of a sound wave from its mean value, which is experienced as the loudness of the sound.


In sound system applications, an analog electrical signal represents the sound in its exact continuous form (non-digitized). Likewise, an analog device is an electronic component that processes analog signals in their continuous form.

Articulation Class (AC)

A measure for rating the attenuation of reflected speech passing over the top of wall partitions or furniture into the adjoining workstations. A ceiling system with AC < 150 is low performance, whereas one with AC >180 is high performance.

Articulation Index (AI)

A measure for rating speech intelligibility. An AI < 0.05 is representative of very poor speech intelligibility, and an AI > 0.80 represents good speech intelligibility. The Speech Privacy Index (PI) is derived from the AI


Standard specification for zinc-coated (galvanized) carbon steel wire (aka hanger wire). For more information, visit


Standard specification for steel sheet, zinc-coated (galvanized) or zinc-iron alloy-coated (galvannealed) by the Hot Dip Process. For more information, visit


Environmental performance test method. For more information, visit


Test methods for strength properties of prefabricated architectural acoustical tile or lay-in ceiling panels. For more information, visit


Standard test method for sound absorption and sound absorption coefficients by the reverberation room method. For more information, visit


Standard test method for steadystate heat flux measurements and thermal transmission properties by means of the heat flow meter apparatus. For more information, visit


Test method for airflow resistance of acoustical materials. For more information, visit


Standard specification for metal suspension systems for acoustical tile and lay-in ceilings. For more information, visit


Standard practice for installation of metal ceiling suspension systems for acoustical tile and lay-in panel. For more information, visit


Standard specification for drywall furring products.For more information, visit


Standard test method for evaluating degree of rust. For more information, visit

ASTM D1037

Standard test method for evaluating properties of impact resistance. For more information, visit

ASTM D2486

Standard test method for scrub resistance of painted surfaces. For more information, visit

ASTM D3273

Standard test method for resistance to growth of mold on the surface of interior coatings in an environmental chamber. For more information, visit

ASTM D4828

Standard test method for practical washability of organic coatings. For more information, visit


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


Method for laboratory measurement of airborne sound transmission loss of building partitions. For more information, visit


Standard method for testing of water vapor transmission. For more information, visit


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


Standard test method for behavior of materials in a vertical tube furnace (aka combustibility test method; often used for Coast Guard applications). For more information, visit


Standard terminology relating to fire standards. For more information, visit


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


Standard practices for mounting specimens during sound absorption tests.For more information, visit

ASTM E1110

Standard specification for the determination of Articulation Class. For more information, visit

ASTM E1111

Standard specification for measuring the inter-zone attenuation of ceiling systems.For more information, visit

ASTM E1130

Standard test method for objective measurement of Speech Privacy in open offices using the Articulation Index. For more information, visit

ASTM E1179

Specification for Sound Sources Used for Testing Open Office Components and Systems. For more information, visit

ASTM E1264

Standard for the classification of acoustical ceiling products.  For more information, visit

ASTM E1375

Standard Test Method for Measuring the Interzone Attenuation of Furniture Panels Used as Acoustical Barriers. For more information, visit

ASTM E1376

Standard Test Method for Measuring the Interzone Attenuation of Sound Reflected by Wall Finishes and Furniture Panels. For more information, visit

ASTM E1414

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

ASTM E1477

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


Reduction in sound level (loudness) as a result of: 1. increased distance from sound source 2. partial sound absorption after reflection off a surface 3. sound passing through a barrier material. 

Audible Frequency Range

The range of frequencies which can be detected by an individual with normal hearing sensitivity. The range of audibility spans from 20Hz to 20 kHz for someone with perfect hearing, and is often reduced significantly at high frequency as a result of “hearing loss."

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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."


Any material or system that blocks or reduces the transmitted sound level as it passes through the material. A poor barrier material will provide a transmission loss TL < 10 dB, whereas a good material will have a TL > 20 dB for partial height barriers and TL > 50 dB for full height barriers, at the frequencies of interest. Both STC and CAC are measures of acoustical barrier performance.

Bevel Edge

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


Ceiling panels with Bioblock performance resist the growth of mold and mildew.


Health Zone ceiling panels with Bioblock Plus performance resist the growth of mold and mildew, and resist odor and stain causing bacterial growth.


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

Brightness Ratio

Brightness ratio is a measure of the quality of a lighting installation. It is an important measure of indirect lighting. A good indirect lighting system has a ceiling brightness ratio of less than 10 to 1.

Broad Band Noise

Noise consisting of a large number of low, mid, and high frequency components, none of which is individually dominant. 


The upper ridge of the main 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)

;A measure for rating the performance of a ceiling system as a barrier to airborne sound transmission through a common plenum between adjacent closed spaces, such as private offices, and open spaces used for collaboration and focus areas. A ceiling system with a CAC < 25 is considered low performance, whereas one with CAC > 35 is high performance.

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.


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," or "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.

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A unit to measure the intensity, or loudness, of a sound  on a logarithimic scale from zero for the least perceptible sound to about 130 for the average pain level.


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

Demountable Partition / Rrelocatable 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.

Directivity Index

A measure for rating the directionality of a particular sound source in a specific direction relative to the level that would be radiated by a perfectly symmetrical sound source of the same power.

Double Web

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

Download Access System

Direct access is achieved by removing individual units by hand or may require 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.

Duty Classification

Load carrying capability of grid main beams (per ASTM C635) pounds per lineal 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 Joints

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 or rail 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 facings are typically used.


Fire resistant 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 E119.


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 E84 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 E1264:

Flame Spread Smoke ASTM E1264


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″.


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.


The repetition rate of a sound wave measured in cycles per second, which is usually expressed in Hertz (Hz). The audible frequency range for normal hearing individual spans from 20Hz to 20 kHz. Frequency is that characteristic of a sound which is perceived by a listener as the “pitch”.

Furniture Panels

The partial height sound screens used to enclose an open office cubicle. Three factors have acoustical importance: the NRC, STC and height of the panels, where panels < 48” are poor, and panels > 72” are very good.

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

Gasketed Grid

Ceiling suspension system that has a gasketing attached to the top side 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 gauge) galvanized, soft annealed steel wire, conforming to ASTM A 641M or A 641. Heavier gauge 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-copper 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 installations in which the quantities and weights of ceiling fixtures (lights, air diffusers, etc.) are greater than those for an ordinary commercial structure.

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 the western United States. Publishes the Uniform Building Code.

Illuminance Levels

 Illuminance is the quantity of light falling onto a surface. It is measured in footcandles or lux (metric measure). One footcandle 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 resistant 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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A tile edge detail with two kerfed sides and two cut sides. 


A tile edge detail with all four sides kerfed and cut.


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 C636.

Light Loss Factor (LLF)

Used to calculate illuminance loss after a given period of time and under given conditions, such as, expected lamp light depreciation, expected lamp burn out, room surface dirt accumulation and ballast performance factors.

Light Reflectance (LR)

Light reflectance is a fundamental property of a material. It is a measure of a material’s ability to reflect visible light. The measure of light reflectance is that fraction of the specified incident light striking a surface that is reflected by the surface. (Defined in ASTM E1477).

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 bearing member of a ceiling system.


The quantity of light reflecting (or emitting) from a surface in the direction of the viewer. It is measured in foot-lamberts or candela/m2 (metric measure). Luminance is a measure of brightness.

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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.

Masking Sound

Electronically generated background sound of a specified level and frequency content, that is introduced into occupied environments to provide masking of intrusive noises and to enhance speech privacy.

Mineral Wool

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


Cross tee end detail that 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 IBC Seismic Design Category C.

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NC40 Curve

This specific NC curve has been used for years as the basis of design for electronic masking sound systems. The NC 40 curve is typically “rolled down” below 100 Hz, and above 5 kHz.


Abbreviation for the National Fire Protection Association.

Noise Criterion / NC Curves

A family of noise rating curves specifying the level and frequency content of background noise which will have a varying degree of acceptability for occupied architectural spaces such as offices.

Noise Reduction Coefficient (NRC)

A measure for rating the overall sound absorption of a material when used in an enclosed architectural space where sound is reflected at many angles of incidence. A ceiling system with an NRC < .50 is low performance, an NRC > .70 is high performance. NRC is important in any space where reverberation time and noise levels are an issue.    

Nonspecular Surface

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

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Octave Band

This is a continuous band of frequencies which span a range such that the highest frequency in the band is twice the lowest frequency. The audio frequency range is separated into octave bands as a matter of convenience, and each band is individually specified by its center frequency, e.g. 63 Hz, 125 Hz, 250 Hz, 500 Hz 1 kHz, 2 kHz, 4 kHz, 8 kHz, and 16 kHz.

Open Plan Office

An office design which is characterized by the application of partial-height furniture panels to enclose a work area into a cubicle, and the layout of many such cubicles within a large open room.


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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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 a wall, door, window, roof or floor-ceiling assembly, that separates one space from another.


An improvement in the main beam bulb design from a rectangular shape to one that culminates to a point, or peak. Unique profile increases strength and stability of grid during installation.

Perimeter Trim

Right angle shaped grid components, either simple or stepped bends, installed around the ceiling perimter, flush to the abutting vertical surface to accommodate suspended ceiling tiles and grid.

Pink Noise

Noise having equal energy per octave band; typically used as the source signal for tuning a masking sound system.

Plan View

An architectural drawing showing the layout of a space e.g. open office, as would be viewed looking vertically down into the space.


The ceiling plenum is the volume defined by the area above the back of the ceiling tile, and below the bottom of the structural slab above. Within this plenum is usually found a combination of HVAC ducts, electrical and electronic conduits, water pipes, traditional masking sound speakers, etc.

Privacy Index (PI)

A measure for rating the speech privacy performance of an architectural space (or lack of speech intelligibility) where the PI is calculated from the Articulation Index (AI) according to the following: PI = (1 – AI) * 100%. A privacy level of PI > 95% represents confidential speech privacy, a PI between 95 – 80% represent normal or non-intrusive privacy, and PI < 80% is poor privacy.

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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 in this catalog were determined by the ASTM C 518 test method. Values are reported at a mean temperature of 75° F (24° C), and as the inverse of BTU/hr • sf • °F (imperial units), and Watts/m2 • °C (metric units).


The persistence of sound in an enclosed space after the source of the sound has stopped. The level of the reverberant sound within a room is dependent on both the volume of the room and the amount of sound absorption installed within the room, such that large hard-surfaced rooms are "louder" than small well-treated rooms.

Reverberation Time

Time required for a sound to decay to a value one millionth of its original intensity or to drop 60 dB. For example,  an RT60 < 1 sec. is beneficial for good speech intelligibility, whereas RT60 > 2.5 sec is appropriate for symphony music.

Room Criterion / RC Curves

A family of noise rating curves specifying the level and frequency content of background noise from HVAC equipment which will have a varying degree of acceptability for occupied architectural spaces such as offices.

Rotary Stitching

Process by which two vertical layers (double web) of steel are stitched or bonded together to form a 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′ and 2′ x 4′ panels look like 12″ x 12″ tile.


For applications where cleanliness is a priority, tiles may require cleaning beyond normal maintenance procedures. Ceilings with special facing material such as vinyl film offer superior performance. Metal ceilings may also be used for these applications. The accepted test procedure is the Scrubbability Test ASTM D2486.

Section View

An architectural drawing showing the vertical layout of a space e.g. open office, as would be viewed looking horizontally across the space.

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.

Shadow Molding

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

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 E84 test of its surface burning characteristics.

Sound Spectrum

A graphical representation of sound, showing the level of the sound as a function of frequency over the audio frequency range.

Sound Transmission Class (STC)

A measure for rating the performance of a wall system as a barrier to airborne sound transmission between adjacent closed spaces, such as offices. A wally system with an STC < 35 is considered low performance, whereas one with an STC > 55 is high performance. STC is the wall equivalent of CAC.

Sound Transmission Loss (TL)

The number of sound decibels that are stopped by a wall, structure, or other material at a given frequency as measured in  1/3 octave bands. The TL in 1/3 OB’s is used to calculate the STC.

Speech Privacy Level

Several layers of speech privacy are defined in the ASTM standards including: 1) Confidential privacy - speech sounds can be heard but not understood, 2) Normal or non-intrusive privacy – speech can be occasionally heard and understood but is generally non-intrusive, 3) Poor privacy – most nearby conversations can be heard and understood.

Speech Weighting Factors

These are the Articulation Index weighting factors presented in ANSI S3.5 (1969). These factors represent the frequency dependency of speech intelligibility being based on the vowels at low frequency carrying less intelligibility than the consonants at high frequency.


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

Provides a tee to tee lock. 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)


Main beam end detail that is a staked-on clip to splice main beams together. This clip provides a strong, secure connection that is easy to remove and relocate.

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.

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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 °C (60 to 85 °F) 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. 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.

Transformer Tap

Refers to the power setting available on a step-down transformer (e.g. 1 watt, 2 watt, 4 watt, etc.) used in high voltage distributed sound systems (e.g. 70v, 50v, and 25v amplifier systems). The transformer is usually located on the loudspeaker.

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UBC 25-2

Uniform Building Code (seismic standard).

UL 580

Wind uplift test (Class 15 – 15 lbs/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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An edge design that provides downward accessibility. The Vector edge detail provides a thin 1/4″ reveal resulting in a clean upscale visual.

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For applications where cleanliness is important, acoustical units may require cleaning beyond normal maintenance procedures. Some acoustical panels with special surfaces offer superior wash resistance without compromising panel finish integrity. The accepted test procedure is the Washability Test ASTM D4828.

Watt (W)

The SI unit of power, equivalent to one joule per second; The power handling capability of amplifiers (output power) and loudspeakers (input power) is given in watts. Power in watts is related to the combination of the driving voltage and the current handling capabilities of the devices.

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.

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Cross tee and detail that is staked on and provides a secure lock connection; tee to tee stab insertion, easy to remove, reuse and relocate.  Meets IBC Seismic Design Category DEF.

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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.

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