Acoustics

Question 1

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

Answer 1

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

Question 2

What can compromise acoustic assemblies? How to fix it?

Answer 2

Openings - penetrations must be sealed with acoustic sealants

Question 3

Strategies to help mitigate the transference of sound in partitions?

Answer 3

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

Question 4

db

Answer 4

decibels - measure intensity sound

Question 5

htz

Answer 5

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

Question 6

STC

Answer 6

sound transmission class
Ability of a material of assembly to block sound

Question 7

NRC

Answer 7

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

Question 8

IIC

Answer 8

Impact Insulation Class

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

Question 9

OBC flame spread rating limitations for group D occupancy - walls

Answer 9

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

Question 10

OBC flame spread rating limitations for group D occupancy - ceilings

Answer 10

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

Question 11

Acoustical ceiling tiles fire rating?

Answer 11

Nearly all has a Class A rating

Question 12

What means to have requirement for fire rated ceiling?

Answer 12

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

Question 13

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

Answer 13

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.

Question 14

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

Answer 14

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

Question 15

What is the NRC of ceiling tiles?

Answer 15

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

Question 16

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

Answer 16

The ceiling

Question 17

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

Answer 17

Walls

Question 18

CAC

Answer 18

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)

Question 19

AC rating

Answer 19

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

Question 20

Should paint be applied on acoustical ceiling tiles? Why?

Answer 20

No, painting destroys the acoustical value of the tiles

Question 21

Another method to achieve sound attenuation?

Answer 21

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

Question 22

Sound masking levels

Answer 22

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

Question 23

Where Sound masking devices may be placed?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Examples of modifications to noise causing behaviour?

Answer 26

Use meeting rooms instead of bullpens | Reduce volume of telephone rings

Question 27

Examples of actions to ABSORB sound? 5 items

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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)

Question 30

What is the ABC's of acoustics?

Answer 30

Absorb Block Cover

Question 31

What does sound masking (cover) do?

Answer 31

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

Question 32

Waves of sound configuration related to frequency?

Answer 32

Long wave length - low frequency | Short wave length - high frequency

Question 33

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

Answer 33

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

Question 34

Range of human hearing in hertz?

Answer 34

About 80 to 10,000 hertz

Question 35

What is ambient or background noise level?

Answer 35

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

Question 36

Acoustics principles - 3

Answer 36

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

Question 37

What happens to sound when it reaches a surface?

Answer 37

Partially reflected Partially absorbed Partially transmitted

Question 38

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

Answer 38

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

Question 39

Methods for achieving sound control between rooms

Answer 39

Space planning: | Construction: floor to wall assemblies

Question 40

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

Answer 40

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

Question 41

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

Answer 41

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

Question 42

Sound Isolation Minimum requirements:

Answer 42

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)

Question 43

Tips for sound attenuation planning

Answer 43

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 ($$$)