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irt301 test ii > WEEK 7 > Flashcards

WEEK 7 Flashcards

1
Q

Sound travels in _______

A

waves

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2
Q

Long wavelength = ______

A

low frequency

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3
Q

short wavelength = _______

A

high frequency

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4
Q

What is sound wave frequency measured in?

A

hertz (Hz)

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5
Q

Human ear is more sensitive to: ______, ________ and ______.

A

low frequencies; high and middle frequencies; all frequencies

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6
Q

What is ambient or background noise level?

A

It is the totality of all sounds within the room when the room is unoccupied

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7
Q

What are the ABC’s of Acoustics?

A

Absorb - materials, Block - Space Planning and Cover - Sound Masking

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8
Q

Reflection

A

Sound is redirected from hard surfaces with little attenuation

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9
Q

Absorption

A

The degree of absorption is dependent on the material chosen

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10
Q

Diffusion

A

Scatters sound, reduces echoing and evens background noise

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11
Q

What does NRC stand for?

A

Noise Reduction Coefficient; the degree of sound absorption of a material

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12
Q

What does a NRC of 1 mean?

A

Surface absorbs 100% of the sound (perfect absorption)

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13
Q

What does a NRC of 0 mean?

A

Surface absorbs 0% of the sound (perfect reflection)

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14
Q

What is the NRC of Gypsum board walls?

A

0.05

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15
Q

What is the NRC of 5/8”

suspended acoustic tile?

A

0.60

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16
Q

What is the NRC of 1” suspended acoustic tile?

A

0.90

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17
Q

What are the different ways for blocking sound through space planning?

A

zone activities of similar noise level and use, use utility spaces as buffers; use closets and bookshelves to separate activities and to keep furniture away from common walls; offset doors; minimize area of partition between rooms ad add absorption to quiet room

18
Q

What does STC Rating stand for?

A

Sound Transmission Class: ability of a material of assembly to block sound

19
Q

What does STC Rating 25 mean?

A

Normal speech can be clearly heard through the barrier

20
Q

What does STC Rating 30 mean?

A

Loud speech can be heard and understood fairly well

21
Q

What does STC Rating 35 mean?

A

Loud speech is not intelligible but can be heard

22
Q

What does STC Rating 42-45 mean?

A

Loud speech can only be faintly heard, and normal speech cannot be heard

23
Q

What does STC Rating 46-50 mean?

A

Loud speech is not audible and loud sounds other than speech and only be heard faintly, if at all

24
Q

Where is an STC Rating of 50-55 used in?

A

Executive areas, doctors’ suites, personnel offices, large conference rooms to satisfy confidential privacy requirements

25
Q

Where is an STC Rating of 45-50 used in?

A

Normal offices, regular conference rooms for group meetings to satisfy normal privacy requirements

26
Q

Where is an STC Rating of 40-45 used in?

A

Large general business offices, computer workstation areas, banking floors for normal privacy

27
Q

Tips for Acoustical Paritions

A
  • insulation is cheaper than layers of GWB
  • use the smallest size metal stud possible
  • expensive if you use a type X or Fire Code C GWB in a rated wall that is in a location that doesn’t need a rating
28
Q

Slab to ______ partitions provide the best sound, but are _______.

A

Slab; expensive

29
Q

Sound is produced __________.

A

when an object vibrates

30
Q

Sound attenuation is achieved in a metal stud partition by:

A
  • adding more layers of wallboard (mass)
  • using resilient channels (dampening)
  • using batt insulation within the stud cavity (absorption); or
  • a combination of these elements
31
Q

Compromise of acoustic assemblies occurs _______ and penetrations must be sealed with _________.

A

in openings; acoustic sealants

32
Q

Partition strategies to help mitigate the transference of sound:

A
  • running the partition slab to slab through the ceiling or raise floor provides the highest level of sound separation
  • 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) or
  • suspending sheet lead from the structural floor above down to the ceiling
33
Q

db

A

decibels; unit of measurement for the intensity of sound

34
Q

IIC

A

Impact Insulation Class: measure of an assembly’s resistance to the transmission of structure-borne or impact noise

35
Q

A ceiling tile must meet _____________.

A

the particular flame spread rating limitations for the particular occupancy groun (Ex. Residential - D occupancy)

36
Q

Nearly all acoustical ceiling tiles have _________

A

a Class A rating

37
Q

What happens if a fire rated ceiling is require?

A

The ceiling tiles are part of a complete floor/ceiling or roof/ceiling assembly that is rated

38
Q

Both the ceiling tiles and ________ must be rated, _______________.

A

grid system; which includes hold-down clops to keep the panels in place and expansion slot to allow the grid to expand when subjected to heat

39
Q

In a rated ceiling, there is a ______________.

A

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

40
Q

Are ceiling tiles good reflectors of absorbers?

A

Absorbers; measured in NRC; most tiles have a NRC of 50 or greater

41
Q

What is the difference between large open offices or small offices with regards to absorbing sound?

A

In large open offices, the ceiling is the best surface to absorb sound while in small offices, walls are used to absorb sound.

42
Q

CAC

A

Ceiling Attenuation class; ceiling tiles are less able to prevent sound transmissions

irt301 test ii (3 decks)

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