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IRT301 > Acoustics > Flashcards

Acoustics Flashcards

1
Q

3 ways sound attenuation is achieved in a metal stud partition:

A

Mass: adding more layers of wallboard
Absorption: using batt insulation within the stud cavity
Dampening: using resilient channels

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2
Q

What can compromise acoustic assemblies? How to fix it?

A

Openings - penetrations must be sealed with acoustic sealants

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3
Q

Strategies to help mitigate the transference of sound in partitions?

A

1) Running the partition slab to slab through ceiling or raised floor provides the highest le el of sound separation
2) Suspending a partition from the structural floor above down to the top of the ceiling grid is also effective(which is cheaper than a slab to slab wall)
3) Suspending sheet lead from the structural floor above down to the ceiling

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4
Q

db

A

decibels - measure intensity sound

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5
Q

htz

A

pitch of sound measured in number of cycles (vibrations per second

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6
Q

STC

A 
sound transmission class
Ability of a material of assembly to block sound
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7
Q

NRC

A

Noice Reduction Coefficient - the degree of sound absorption of a material
0= perfect reflection
1 = perfect absorption

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8
Q

IIC

A

Impact Insulation Class

Measure of an assembly’s resistance to the transmission of structure-borne or impact noise

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9
Q

OBC flame spread rating limitations for group D occupancy - walls

A

1) Combustible interior finish is permitted in a required noncombustible construction if said finish is less than 1mm thickness (paint, wall paper…)
2) Other wall finishes (not foamed plastic) are permitted if they are less than 25mm thick and has a flame-spread rating not more than 150

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10
Q

OBC flame spread rating limitations for group D occupancy - ceilings

A

Combustible ceiling finishes (other than foamed plastic) are permitted in a noncombustible construction if:

1) less than 25mm thick - excepted for fire-retardant treated wood battens
2) flame-spread rating less than 25 , exceptions: fire-retardant treated wood

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11
Q

Acoustical ceiling tiles fire rating?

A

Nearly all has a Class A rating

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12
Q

What means to have requirement for fire rated ceiling?

A

It means that the ceiling tiles are part of a complete floor/ceiling or roof/ceiling assembly that is rated

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13
Q

which parts of the suspended acoustic ceiling assembly must be rated?

A

Both the ceiling tiles and grid system, which includes hold-down clips to keep the panels in place and expansion slots to allow the grid to expand when subjected to heat.

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14
Q

In a rated ceiling are there any limit to number and size of openings?

A

Yes, there is a limit to the number and size of openings in the ceiling for items such as duct opening, lights and electrical boxes

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15
Q

What is the NRC of ceiling tiles?

A

Most tiles have a NRC of 50 or greater which make them good sound absorbers.

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16
Q

Which surface is the best to absorb sound in large open offices?

A

The ceiling

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17
Q

Which surfaces are usually used as sound absorbers in small offices?

A

Walls

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18
Q

CAC

A

Ceiling Attenuation class - ability of ceiling tiles to prevent sound from passing through the panel and the plenum into an adjacent space (although they are less able to prevent sound transmission)

19
Q

AC rating

A

Articulation Class - measurement of sound reflected from ceiling to adjacent workspaces in open office plans. Indicates how much or how little conversation one would be able to decipher

20
Q

Should paint be applied on acoustical ceiling tiles? Why?

A

No, painting destroys the acoustical value of the tiles

21
Q

Another method to achieve sound attenuation?

A

Laying blankets on top of the tile for a distance of 4’ on either side of the partition (not an ideal solution)

22
Q

Sound masking levels

A

Should be 45-48dB - random levels throughout a space are good

23
Q

Where Sound masking devices may be placed?

A

Within the plenum space or hung in open ceiling - remember to put them in closed offices as well

24
Q

Example of sound masking device for individual cubicles - what it does?

A

Herman Miller’s individual vocal privacy device (size of a clock radio) - multiplies your voice and sends your randomized voice out with your natural voice and the combination is impossible to decipher

25
Q

How workstations should be oriented so that speech is directed way from neighbours?

A

Workstations should be oriented so that occupants working in adjacent workstations should be seated so that they are facing away from each other.

26
Q

Examples of modifications to noise causing behaviour?

A

Use meeting rooms instead of bullpens

Reduce volume of telephone rings

27
Q

Examples of actions to ABSORB sound? 5 items

A

1) Adding absorptive ceiling tiles
Invest in good acoustic tile and ensure consistent coverage throughout your facility
2) Limit lighting system’s impact on the ceilings performance (select indirect system that incorporates a minimum of fixtures)
3) Minimize use of hard materials (glass/metals)
4) Use Absorptive workstation partitions
5) Install soft flooring

28
Q

Examples of actions to BLOCK sound in open plans? 3 items

A

1) Locate noisy office machines and high-activity areas (such as call centres) in remote or isolated areas.
2) Maximize distance between employees and minimize direct paths of sound transmission (seating employees facing away from each others.
3) Use taller partitions (60-65 inches - 1.5 to 1.65m) that extend beyond seated head height

29
Q

Example of action to COVER sound transmission, what it does?

A

1) Install a sound masking system - series of loudspeakers installed in a grid-like pattern in the ceiling (Distribute a comfortable background sound - designed to mask the frequencies in speech and cover unwanted noises)

30
Q

What is the ABC’s of acoustics?

A

Absorb
Block
Cover

31
Q

What does sound masking (cover) do?

A

1) Noise control - reduces the dynamic range (noises beneath the masking are imperceptible and the impact of those above is lessened)
2) Speech privacy - reduces the distance from which speech can be noticeable or intelligible
3) Acoustic consistency

32
Q

Waves of sound configuration related to frequency?

A

Long wave length - low frequency

Short wave length - high frequency

33
Q

What does uncontrolled noise and lack of speech do in an work place?

A

Negatively affect concentration, slowing task performance, increasing error and threatening the continuity of creative thought.
Impacts comfort, stress levels and morale

34
Q

Range of human hearing in hertz?

A

About 80 to 10,000 hertz

35
Q

What is ambient or background noise level?

A

Is the totality of all sounds within the room when the room in unoccupied

36
Q

Acoustics principles - 3

A

Reflection - sound is redirected from hard surfaces with little attenuation
Absorption - the degree of absorption in dependent on the material chosen
Difussion - Scatters sound, reduces echoing and evens background noise

37
Q

What happens to sound when it reaches a surface?

A

Partially reflected
Partially absorbed
Partially transmitted

38
Q

Methods for achieving sound control within a room - large office?

A

Suspended Acoustic Tiles - NRC .60 together or not with other ceiling treatments - most effective
Acoustic wall tiles or panels

39
Q

Methods for achieving sound control between rooms

A

Space planning:

Construction: floor to wall assemblies

40
Q

Space planning strategies to control sound transmission between rooms - 5 items

A

1-Zone activities of similar noise level and use
2-Use utility spaces as buffers
3-Use closets and bookshelves to separate activities and to keep furniture away from common walls
4-Offset doors
5-Minimize area of partition between rooms and add absorption to quiet room

41
Q

Effect of Barrier STC Ratings (25, 30, 35, 42-45, 46-50) on Hearing?

A

STC25 - Normal speech can be clearly heard through the barrier
STC30: Loud speech can be heard and understood fairly well
STC35: Loud speech is not intelligible but can be heard
STC42-45: Loud speech can only be faintly heard, and normal speech cannot be heard
STC46-50: Loud speech is not audible and loud sounds other than speech can only be heard faintly, if at all

42
Q

Sound Isolation Minimum requirements:

A

STC 50-55 - where confidential privacy requirements (doctor’s suites, executive areas, personnel office, large conference rooms)
STC 45-50 - normal privacy requirements (offices, regular conference rooms for group meetings)
STC 40-45 - Normal privacy (large general business offices, computer workstation areas, banking floors)

43
Q

Tips for sound attenuation planning

A

Insulation is cheaper than layers of GWB
Use the smallest size metal stud possible
If you use a rated wall in a location that doesn’t need a rating, don’t use type X or Fire Code C GBW ($$$)

IRT301 (5 decks)

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