Sound Control

Below find detailed information concerning each of the following topics:

 

Design considerations

Sound travels in all directions and is deflected off of hard surfaces. All office components (walls and roof) as well as the surrounding environment must be considered in your design...
  • Group noisy equipment together in the same area.
  • Choose equipment that generates less noise.
  • Consider enclosing the noisy equipment with partitions.
  • Consider the travel of the sound and the acoustical
    properties of the area.
  • Locate your office away from the noisy areas.
  • Choose an area that is isolated and protected.
  • Design the office with doors or windows facing away
    from the noise source.
  • Design the office with matching sound deadening components.
  • Place closets or store rooms etc. on the walls closest
    to the noise source.
  • It is usually less expensive to avoid noise problems than to correct them

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Sound Intensity

A comparison table of relational sound intensities. Measured in decibel units (db).

  Noise
Source		 Decibel
Level		 Intensity /
Energy Units
 
Jet Aircraft
140
100,000,000,000,000
 
Pain threshold
130
10,000,000,000,000
 
 
120
1,000,000,000,000
   
110
100,000,000,000
 
Heavy Manufacturing
100
10,000,000,000
 
Medium Manufacturing
90
1,000,000,000
 
Light Manufacturing
80
100,000,000
 
Warehouse
70
10,000,000
 
Normal Speech
60
1,000,000
 
Quiet Office
50
100,000
 
Private Office
40
10,000
   
30
1,000
 
Empty Theater
20
100
   
10
10
 
Hearing Threshold
0
1

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OSHA regulations

Manufacturing plants with noise levels above 90 decibels are required by OSHA to minimize the working time in those areas and to provide ear plug protection. Installing sound controlled rooms will maximize the productive time in an area.

OSHA Standards:

  Decibel level Allowed Work Shift
 
90dB
 8 Hours
 
92dB
6 Hours
 
95dB
4 Hours
 
97dB
3 Hours
 
100dB
2 Hours
 
102dB
1.5 Hours
 
105dB
1 Hour
 
110dB
30 Minutes
 
115dB
15 Minutes

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sound definitions.

ATTENUATION -
Reduction or lessening.

TRANSMISSION LOSS (TL) -
This refers to attenuation of sound passing through construction when tested according to ASTM E90. The actual TL graph provides the best rating method. Sound transmission through walls varies with the frequency, weight or mass and stiffness of the construction. Theoretically the transmission loss varies at the rate of 6 dB per doubling (or halving) of the weight and varies 5 dB for each doubling of the air space (minimum effective space is 2").

NOISE REDUCTION -
The actual difference in the sound pressure level between two spaces being considered. It is what the ear hears and what we are interested in. It is dependent on the TL of the walls and the sound absorption present.

SOUND TRANSMISSION CLASS (STC) -
Testing method is ASTM E90 - Airborne Sound Transmission Loss. This is a rating system which compares the transmission loss test curve for a construction with a "standard contour" which reflects known subjective response to the TL performance. The contour is fitted to the test curve of the construction, and the relative vertical position of the contour determines the sound transmission class. This is used for ranking materials. The standard curve fitted to the actual TL can not have a deficiency of more than 8 decibels. The inherent problem with this ranking standard is that building materials commonly have coincidence points at one particular frequency showing a deficiency of 8 or more points. The cause of the deficiency is usually unexplainable. The results are a drop in the STC value which lowers the ranking. It is possible for a material to have a lower STC value than another and attenuate sound better in 17 of the 18 testing frequencies. For this reason we strongly suggest the use of the actual TL data when determining the appropriate material to use for any application and a field measurement for the applicable noise frequencies.

SOUND FREQUENCY -
Octave band frequencies measured in cycles per second or Hertz (Hz).

OCTAVE -
a frequency ratio of 2:1. For example from middle C (261hz) to one octave higher 522 or one octave lower 130.

SOUND ABSORPTION COEFFICIENT -
This is the ratio of sound absorbing effectiveness (at a specific frequency) of one square foot of material compared to one square foot of perfectly absorptive material. It is expressed in a decimal value and is usually measured at 125, 250, 500, 1000, 2000 and 4000 cycles.

NOISE REDUCTION COEFFICIENT (NRC) -
This is the average sound absorption of the 4 center frequencies, 250, 500, 1000 and 2000 rounded to the nearest .05.

REVERBERATION -
The persistence of sound after the source has stopped. High speed multiple reflections within a space.

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Isolation Criteria

General Sound Isolation Criteria is determined by:

  • Location
  • Use
  • Minimum STC (see below for definition of STC)

Isolation Criteria Table

  Location Use Minimum STC
 
Light duty warehouse (70dB)
Executive Offices
20
    Normal Offices 15
    General Offices 10
    Shop 5
 
Light manufacturing (80dB)
Executive Offices
30
    Normal Offices 25
    General Offices 20
    Shop 15
 
Medium manufacturing
Executive Offices
40
    Normal Offices 35
    General Offices 30
    Shop 25
 
Heavy manufacturing
Executive Offices
50
    Normal Offices 45
    General Offices 40
    Shop 35

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sound Transmission Values (stc)

Below is a Sound Transmission Class (STC) Value list of National Partitions' Standard Components.

STC Value of Standard Components

  Material STC Value
 
3/16" Tempered Glass
25
 
1/4" Laminated Glass
35
 
1/2" Insulated Glass
32
 
Hollow Core Door
25
 
Solid Core Door
35
 
3/16" Hardboard Wall Panel
25
 
5/8" Gypsum Wall Panel
35
 
SOUND SILENCER Wall Panel
45
 
Roof Deck with Mineral Tile Ceiling
35
 
SINGLE SHEET - 18 Gage Steel
30
 
SINGLE SHEET - .025 Aluminum
19
 
SINGLE SHEET - Plywood 1/4"
22
 
SINGLE SHEET - Lead 1/16"
34

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sound Frequency

Below, find a list of common sound frequencies.

Common Sound Frequencies

  item Range
 
Span of Human Hearing
0 - 20000 Hz
 
Speech interference range
550 - 5000 Hz
 
Span of AM radio
200 - 5000 Hz
 
Female Voice
600 - 800 Hz
 
Musical "A" Note
440 Hz
 
Musical "High C" Note
4186 Hz
 
Pedal of Pipe Organ
10-20 Hz

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Standard Products

Below, find decibel transmission loss levels for our standard products across a spectrum of sound frequencies.

Glass:

    Tempered Glass - 3/16"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Laminated Glass - 1/2"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Laminated Glass - 1/4"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Laminated Glass - 1/4" --space-- Tempered Glass 3/16"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41

 

Panels:

    Hardboard-HC-Hb Panel 1/8"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Hardboard-HC-Hb Panel 3/16"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Gypsum-HC-Gyp Panel - 5/8"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Steel--Foam--Steel Panel - 26ga.
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Steel--Foam--Gypsum - 5/8"
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Steel--Gypsum--Foam--Gypsum--Steel - 26ga.
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Steel--Gypsum--Stud/FG--Gypsum--Steel - 26ga.
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41
    Aluminum--Foam--Gypsum Panel - .024a.
  Hz
100
 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k
   
23
25
 25 24 28 26 29 31 33 34 34 35 34 30 27 32 37 41

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recommendations

The following illustrations represent the actual transmission loss for the listed products, and shows the recommended STC value for a typical shop office in various environments. The target value is 65 dB. The frequencies have been simplified into 3 major categories (low, mid range and high) rather than the tested 18 frequencies, this will make it easier to choose the proper product without knowing the exact frequencies of a particular area.

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Acoustical Design

Below, find some common considerations for acoustical design:

  • Use absorptive materials on surfaces that may cause objectionable reflection.
  • Seal all holes and openings in walls.
  • Make use of shapes to deflect noise.

The recommended NRC value for most rooms is .65 - .75, special consideration (over .75) should be given to the following rooms:

  • Computer Rooms
  • Accounting Rooms
  • Class Rooms
  • Kitchens

 

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