GreenStep Study Matrix 4: Acoustics

Question 1

NRC Definition

Answer 1

Noise Reduction Coefficient (NRC) is the average value that determines absorptive properties.

Question 2

NRC is addressed in which feature?

Answer 2

80- Sound Reducing Surfaces

Question 3

NRC is related to which room type or surface?

Answer 3

Ceilings:
Open Workspaces: minimum NRC of 0.9 for the entire surface area of the ceiling (excluding lights, skylights, diffusers, beams, joists and grilles).

Conference/Teleconference rooms: minimum NRC of 0.8 on at least 50% of the surface area of the ceiling (excluding lights, skylights, diffusers, beams, joists and grilles).

Vertical Surfaces:
Enclosed Offices/Conference/Teleconference rooms: minimum NRC of 0.8 on at least 25% of
the surface area of interior surrounding walls.

Open workspaces: minimum NRC of 0.8 on at least 25% of the surface area of the surrounding walls.

Partitioned office spaces: partitions reach at least 1.2 m [48 inches] and have a minimum NRC of 0.8.

Question 4

NC Definition

Answer 4

Noise Criteria (NC) define the sound pressure limits of the octave band spectra ranging from 63-8000 Hz. The noise criteria equals the lowest curve which is not exceeded in the spectrum.

Question 5

NC is addressed by which features?

Answer 5

75- Internally Generated Noise

89-Adaptable Spaces

Question 6

NC is related to which room type or surface?

Answer 6

75:
Open Office/Lobbies (Regular Occupancy)- Max NC 40
Enclosed Offices- Max NC 35
Conference Room/Breakout Room- Max NC 30
(25 Recommended)
89:
Privacy NC Mechanical Systems

Question 7

RT60 definition?

Answer 7

Reverberation Time (RT) is it takes for sound to decay. The most commonly used reverberation time is RT60, the time it takes for the sound level to decrease 60 decibels. Additional reverberation time measurements are RT20 and RT30, for decreases of 20 and 30 decibels, respectively.

Question 8

RT60 is addressed by which feature?

Answer 8

78- Reverberation Time

Question 9

RT60 is related to which room type or surface?

Answer 9

Conference Room= .6 seconds (RT60)

Open Workspaces= .5 seconds (RT60)

Question 10

STC is addressed by which feature?

Answer 10

81- Sound Barriers

Question 11

STC is related to which room type or surface?

Answer 11

• Enclosed Offices- Min STC 40 (w/ sound masking)
• Interior Partitions/Walls- Min STC 45 (w/ no sound masking)
• Conference Rooms/Teleconference Rooms- Min 53 on walls adjoining Private Offices, Conference Rooms, Teleconference Rooms