acoustical ceilings laura varjabedian | id206. acoustics understanding a·cous·tic noun the...

Acoustical CeilingsLaura Varjabedian | ID206

AcousticsUnderstanding

• a·cous·tic Noun

• the properties or qualities of a room or building that determine how sound is transmitted in it.

• All materials interact and influence the distribution of sound within a space, which is managed by understanding the way they absorb sound waves

• Ambient sounds: background, present on site or in location• Frequency: measure repetiviness, thought of I terms of pitch

(high-frequency vs low-frequency)

Factors• Echo: reflected sound delayed from original sound, perceived

separately • Flutter Echo: echoes that occur in rapid succession, common

between parallel walls• Reverberation: sound reflections as around bounces around a

space. Lengthen the duration of a sound (hard surfaces)• Focused Sound: the sound within large spaces where the

waves are distorted and focused around specific points. Must be managed with materials to affect its travel

Rating and Measuring• Privacy Index (PI)- measures speech intelligibility.

• PI less than 60% - offers no speech privacy, “poor”• 60-80%- speech is readily understood, “marginally effective”• 80-95%- speech is distracting, requires effort to be understood, “normal” • 95%+ best confidentiality

• Sound Transmission Class (STC): measures sound moving through partitions or barriers • Affected by: mass of materials, thickness, control of flanking and structure-borne paths• STC of 25-30 speech is fairly understood• 35-40- audible but not ineligible • 50- renders loud speech inaudible

• Impact Isolation Class: measure the amount of impact noise blocked by the surface • Measurement of 50 is adequate

• Speech Range Absorbtion (SRA): measures absorbtion of sounds specifically from speech

Ceilings and Sound • Ceilings are often the largest factor within a space to

absorb or reflect sound within an interior space • Sound quality is a combination of the sound absorbed

and the sound reflected • Sound absorption is measured in sabins• More or less, the sound that is not absorbed is reflected• Materials with low sound absorption can be used to

encourage the reflection of sound appropriately • Influenced by distance and time

Systems • Ceiling Attenuation Class (CAC)

• The ability of a ceiling system to block sound transmission

• CAC of 35 is considered a good performance, meaning the construction reduces sound by 35 decibels

• Sound Absorption Coefficient• The percentage of sound that will be absorbed by an

assembly• A rating of 75% means it absorbs 75% of the sound,

sending the other 25% back into the space

Acoustical Tile

• Designed to last (fewer size and finish options)• Installation can be more costly, maintenace is more difficult• Not easily accessible, within above-ceiling areas • Typically 12 x 12 in. with a thickness of ½, 5/8, or ¾ in. • Must consider… fire resistance, high light reflectance, durability, seismic conditions, humidity/ sag

resistance, antimicrobial resistance, recycled content• Articulation Class (AC): measures reflected speech noise that passes over top partitions (wall or

furniture) in adjoining work stations

• Concealed spline ceilings or concealed ceiling suspension systems• Comprised of• a supporting grid (completely concealed) • mineral fiber acoustical tiles (provide an uninterrupted ceiling plane)

• Can also be applied and installed directly on a substrate

Acoustical Tile

Fire Resistance & Fire Rating• Tested with roof or floor construction type by Underwriters Laboratories (UL)• Assigned ratings of 1,2,3, or 4 hours• Structural elements are determined upon existing and available conditions once these

conditions are met

• Tested by 3 ASTM tests• ASTM E 119 Standard Test Methods of Fire Tests of Building Construction and Materials

• Measures in hours the degree to which an assembly, in its entirety, withstands fire and high temps

• ASTM 3 84 Standard Test Methods of Surface Burnings Characteristics of Building Materials • Surface flame spread and smoke development

• Building codes usually requre acoustical ceiling tiles to habe a Class A fire rating

Sound Absorption & Isolation• In an open setting, improves amount of acoustic privacy between partial height rooms/

workspaces • In a closed setting, can improves transmission of sound between rooms

Edge Profiles

• Textures vary from fine to course • Typically white, most colors affect light reflectance of

ceiling

Textures & Colors

• Commonly square or beveled with kerfed (grooved or notched edge)• Squared appears more monolithic when installed, joints are

sometimes obvious• Beveled provide eased edge, slight shadow between tiles. Can

minimize damage during a removal process

Light Reflectance • Illuminance (quantity of light striking a surface) is measured in footcandles, or lux.• Acoustical tiles with high light reflectance (LR) provide greater levels of reflected light from the

ceiling place

Acoustical Panels • Composed of • Prefabricated ceiling units• Metal suspension system

• Commonly used where sound attenuation and accessibility to ceiling plenum space above is desired

• Largely a visual element, impacts the design as well as acoustics • Partitions, light fixtures, ceiling diffusers, sprinklers and other devices can be attached or

installed so the layout must be considered when designing for this type of space • Typically in square and rectangular dimensions ranging from 24 x 24 in. to 24 x 48 in, up to 60 x

60 in. • Thickness varies from 5/8, ¾, and 1 in.• The same considerations apply as in acoustical tiles, but because panels are larger, the

acoustical performance can be improved

Acoustic Panels

Acoustical Panels

Composition• Composition is similar to tiles, water felted, cast or molded, and

nodular, special cases with ceramic and mineral fiber composite• Perforated metal ceiling panels are durable, humidity resistant, and

low maintenance, offering good aesthetics acoustics.

• Square or tegular (reveal) shapes• Easily dropped into place in the suspension system and pushed up to

access ceiling plenum

Edge Detail

Installation• Varies depending on materials and wall intersections and

includes many details concerning the panel edge and suspension into the grid details.

CSI Section

And now for a short quiz! 1. What is the term for the properties that determine how sound is transmitted through a room or building?

Acoustics.

2. What is P.I.?

Privacy Index.

3. Part II: What does this do?

Measures speech intelligibility.

4. What are the two parts that make up Acoustical Tile?

1. Supporting grid2.Mineral Fiber Acoustic Tile

5. Between the two types of Acoustical Ceilings, which is easier to access/ manage?

Panels.