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Sounds Control Specifications

Terms and Definitions

Sound A pressure variation in air that creates an auditory effect.
Noise Unwanted sound, sound without particular value.
Decibel (dB) Unit of sound or noise measurement versus frequency.
Sound Transmission Class (STC) Rating system used to measure the transmission loss (decibel reduction) of various materials. Testing method is ASTM E 90 that compares the transmission loss for the material at the 500Hz range.
Transmission Loss (TL) The reduction of sound passing through materials when tested in accordance to ASTM E 90.
Noise Reduction (NR) This is the actual difference in sound between two areas. The NR is determined by the transmission loss of the material between the two areas.
Noise Reduction Coefficient (NRC) Rating system that measures the ability of materials to absorb sound.

 
 

Design

Starrco prefabricated offices can be extremely effective in dealing with noise problems within a working environment. Listed below are some items to consider when designing for noise control:

  • OSHA requires manufacturing facilities with noise levels at 90 dB and above to limit the amount of time workers are exposed to the noise.
  • The noise reduction capabilities of an office are only as good as its weakest point. If possible, have doors and windows facing away from the noise source. Noise will attack the weakest point of the office. The noise reduction panels making up the office should be approximately equal. In other words, upgrading the walls to sound control panels will not be acoustically effective unless the doors, windows, ceiling, etc., have also been upgraded.

 

Products

Starrco offers modular wall panels with three different constructions. The STC ratings for each available panel construction are shown below. Also shown are the STC ratings for some of the common components of our Prefabricated offices:

Panel Types SP SC DL
SS3000 3″ Thick Panels 22 33 28*
SS3500 3″ Thick Panels 22 33 28*
3068 Pre-Finished Wood Door 26 26
3068 20 gauge Steel Door 30
Window w/1I4″ Tempered Safety Glass 28
Window w/1I4″ Laminated Safety Glass 34
2′ x 4′ Mineral Fiber Ceiling Tile 35-39

 
Please keep in mind the STC ratings are a result of laboratory testing. The actual sound reduction experienced in the field will be less. The amount of reduction achieved depends upon the type and frequency level of the noise source and the quality of the installation.
*Remember, the STC rating represents the decibel reduction at a single frequency level. The 3″ thick panels have superior sound control capabilities at the higher frequency levels.
The chart shown below shows the correlation between some common noise sources and decibel levels. This can help to give some perspective to how loud a particular decibel level may be:

Decibel Level Sound Source
170 Jet Engine
150 Prop. Engine
140 Pain Threshold
130 Jack Hammer
110 Punch Press
90 Busy City Street
70 Business Office
60 Normal Speech
50 Business Office (Private)
40 Library Room
20 Quiet Speech (Whisper)
0 Hearing Threshold

 
As previously mentioned OSHA limits the amount of time workers may be exposed to noise levels of 90 dB or greater. Pre-Engineered “break-rooms” located on the production floor can help meet exposure requirements while maximizing the available productive time of workers In an area.


 

OSHA Standards

Allowable Work Hours Decibel Level
8 90
6 92
4 95
3 97
2 100
1.5 102
1 105
0.5 110
0.25 115