Noise Curtains and Absorption Materials

Noise curtains and absorption materials are designed to reduce noise exposure by absorbing sound.

Description:

Noise curtains and absorption materials are engineering controls that can reduce noise exposure. Noise curtains and absorption materials are constructed of soft, porous, low-density materials such as foam and fiberglass and may be supported by frames constructed of high gauge steel, aluminum or zinc. These products reduce noise by blocking or absorbing sound.

Through the use of specially designed noise curtains and sound absorbing materials, noise levels and exposures can be reduced. However, sound pressure levels may still be above the OSHA Permissible Exposure Limit (PEL) and workers may need to wear hearing protection for more than intermittent visits.

The ability of a material or product to block sound at a specific frequency is its transmission loss (TL). Transmission loss ranges from 0 dB, for materials that provide no reduction in sound engery, to greater than 70 decibels (dB) for materials that provide the greatest reduction in sound energy. Tranmission loss is generally measured at frequencies of 125, 250, 500, 1,000, 2,000 and 4,000 Hertz (Hz). Sound transmission class (STC) is a single-number rating used to describe the ability of a material to act as a sound barrier for sounds from 125 to 4,000 Hz.  In addition to blocking sound energy, most barriers and enclosures will also absorb sound. The fraction of sound energy that is absorbed is called the sound absorption coefficient. A particular material’s noise reduction coefficient (NRC) is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz. An NRC of 0 means the surface is a perfect reflector of sound and an NRC of 1.0 means the surface is a perfect absorber of sound. It is possible to have an NRC above 1.0.

Singer Safety Noise Curtains

 

 

 

 

 

 

 

 

 

Model

Cost

Weight (pounds)

Transmission Loss (dBA)

½ #

$280-$380

26-38

6-12

¾ #

$300-$400

34-40

10-16
  • Panel Types: single-sided (1 inch thick quilted fiberglass material), double-sided (2 inches thick quilted fiberglass material)
  • Construction Material: zinc framing, vinyl, fiberglass
  • Sound Absorption Material: SOUND STOPPER (vinyl, fiberglass)
  • Panel Dimensions: 8 feet by 4 feet
  • Optional panel framing available

(SOUND STOPPER is a specially designed absorption material produced by Singer)

 

Singer Safety Absorption Foams. Photo shows top layer of convoluted foam (CAF), middle section of aluminized foam (AMF) and a bottom layer of standard foam (SAF).

 

 

 

 

 

 

 

Model

Cost (per square foot)

Density (pounds per cubic foot)

Aluminized Mylar Foam (also reflects light and heat, keeps out dirt, dust and grease)

$3.78

1.8-2.2

Convoluted Acoustic Foam (absorbs sound more effectively)

$4.00

0.5-4.0

Standard Acoustic Foam (flat foam on both sides)

$3.21

0.5-4.0
  • Transmission Loss: 4-7 dBA
  • Sound Absorption Material: foam
  • Dimensions: 54 inches by 10 feet per roll by 1 inch thick (convoluted foam is sold 4 sheets per box at 54 inches by 27 inches by 1-3 inches thick)

 

dB Engineering Noise Curtains

 

 

 

 

 

 

 

 

 

  • Cost: approximately $600 per panel
  • Weight: 1.3-2.6 pounds per square foot
  • Sound Absorption Material: quilted fiberglass
  • Panel Dimensions: 8 feet by 4 feet
  • Optional framing available

Absorption Coefficients

Product

 Frequency (Hz)

125

250

500

1000

2000

4000

NRC*

BBC Products 1”

0.12

0.47

0.85

0.84

0.64

0.62

0.70

BBC Products 2”

0.07

0.27

0.96

1.13

1.08

0.99

0.85

BSC Products 2”

0.19

0.99

0.96

0.80

0.57

0.33

0.85

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

Sound Transmission Loss (dB)

Product

Thickness (inches)

 Frequency (Hz)

125

250

500

1000

2000

4000

STC*

BBC-13-2”

2

13

20

29

40

50

55

32

BBC-13

1

11

16

24

30

35

35

27

BBC-25-2B

2

19

22

28

40

56

61

33

BSC-25

2

12

16

27

40

44

43

29

BSC-31

2

12

16

23

33

38

39

27

BSC-25-RP

2.5

19

20

28

42

56

62

31

*STC is a single-number rating of a material’s ability to act as a barrier for sounds from 125 to 4,000 Hz.

 

Kinetics Noise Control Curtains

 

 

 

 

 

 

 

Model

Cost

Weight (pounds per square foot)

Dimensions (LxWxH)

KNC

$700-$1,300 per Panel

0.5-2.5

4 feet x 8 or 10 feet x 1 or 2 inches
  • Construction Material: foam, fiberglass, steel, aluminum
  • Absorption Material: foam, fiberglass
  • Optional Framing Available

Absorption Coefficients

 

Frequency (Hz)

Product

125

250

500

1000

2000

4000

NRC*

Q1-1” Quilt

0.12

0.47

0.85

0.84

0.64

0.62

0.70

Q2-2” Quilt

0.08

0.33

0.79

1.02

1.04

1.02

0.80

Q4-4” Quilt

0.30

0.83

1.16

1.18

1.10

1.07

1.10

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz

Sound Transmission Loss (dB)

 

Frequency (Hz)

Product

125

250

500

1000

2000

4000

STC*

KNC-50RB

12

13

16

22

27

32

21

KNC-100RB

13

17

21

28

33

40

26

KNC-50RBQ

6

12

17

27

38

46

23

KNC-100RBQ

10

16

22

30

42

49

27

KNC-50BQQ

7

12

18

31

46

50

24

KNC-100BQQ

11

16

28

41

50

53

29

KNC-200BQQ

16

20

30

40

51

55

33

KNC-50C

8

13

17

22

27

31

20

KNC-100C

4

19

23

28

33

37

26

*STC is a single-number rating of a material’s ability to act as a barrier for sounds from 125 to 4,000 Hz.

 

Industrial Noise Control Noise Curtains

 

 

 

 

 

 

 

 

 

 

  • Cost: $7-10 per square foot
  • Weight: 1.25 to 1.5 pounds per square foot
  • Construction Material: vinyl
  • Absorption Material: Flexi-Sorb
  • Dimensions: 54 inches by custom length by 1 or 2 inches thick
  • Optional framing available

Absorption Coefficients

 

Frequency (Hz)

Product

125

250

500

1000

2000

4000

NRC*

W111P

0.39

0.59

0.87

0.84

0.73

0.59

0.75

W211P

0.53

0.77

0.88

0.77

0.71

0.63

0.80

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

Sound Transmission Loss (dB)

 

Frequency (Hz)

Product

125

250

500

1000

2000

4000

STC*

W111P

17

18

23

28

35

40

28

W211P

18

19

24

29

36

41

29

*STC is a single-number rating of a material’s ability to act as a barrier for sounds from 125 to 4,000 Hz.

 

SONEX Absorption Foams

 

 

 

 

 

 

 

 

 

Model

Cost Per Box

Weight (pounds per cubic foot)

Dimensions per Sheet (inches)

Sheets Per Box

SONEX Classic Urethane

$250-$300

0.7-2.0

24x48x2-4

4-8

SONEX Value Line

$210-$280

0.7

24 x 48 x 1.4-2.4

4-8

SONEX One Unpainted Foam

$200-$530

0.7

24x48x1-3

4-12

SONEX Pyramids*

$220-$360

0.7-2.0

24x24x2-4

4-14

*Open Cell Melamine

  • Construction Material: foam, various coatings
  • Absorption Material: foam

SONEX Classic Absorption Coefficients

 

Frequency (Hz)

Thickness

125

250

500

1000

2000

4000

NRC*

2 inches

0.09

0.29

0.64

0.97

1.05

0.97

0.75

3 inches

0.15

0.42

0.99

1.14

1.10

1.10

0.90

4 inches

0.19

0.59

1.14

1.16

1.11

1.15

1.00

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

SONEX Value Line Absorption Coefficients

 

Frequency (Hz)

Thickness

125

250

500

1000

2000

4000

NRC*

35 millimeters

0.08

0.29

0.73

0.94

0.97

0.89

0.75

53 millimeters

0.17

0.55

1.07

1.15

1.08

1.10

0.85

60 millimeters

0.19

0.62

1.15

1.21

1.14

1.20

1.05

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

SONEX One Absorption Coefficients

 

Frequency (Hz)

Thickness

125

250

500

1000

2000

4000

NRC*

1 inch

0.11

0.17

0.40

0.72

0.79

0.91

0.50

2 inches

0.17

0.30

0.90

1.03

1.08

1.06

0.80

3 inches

0.09

0.71

1.20

1.18

1.12

1.09

1.05

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

SONEX Pyramids Absorption Coefficients

 

Frequency (Hz)

Thickness

125

250

500

1000

2000

4000

NRC*

2 inches

0.07

0.25

0.60

0.94

0.97

1.08

0.70

3 inches

0.09

0.37

0.81

1.01

1.03

1.07

0.80

4 inches

0.18

0.44

0.96

1.14

1.18

1.19

0.95

*NRC is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz.

Risks Addressed:

Over time, exposure to noise levels at or above 85 decibels can lead to permanent hearing loss. The NIOSH Recommended Exposure Limit (REL) for occupational noise is 85 decibels on an A-weighted scale as an 8-hour time weighted average. OSHA limits noise exposure to 90 decibels, also on an A-weighted scale and as an 8-hour time weighted average (U.S. Department of Health and Human Services, 1998). A-weighting is an adjustment that gives lower frequencies less weight or significance than higher frequencies. An A-weighted sound level more closely resembles the human ear’s response to noise.

The American Conference of Governmental Industrial Hygienists (ACGIH) assigned noise a Threshold Limit Value (TLV) of 85 dBA as an 8-hour time weighted average. Exposure to 88 dBA is limited to 4 hour, exposure to 91 dBA is limited to 2 hours, exposure to 94 dBA is limited to 1 hour and so on. (ACGIH, 2013).

TLVs for Noise

 

Duration per Day

Sound Level dBA

Hours

24

80

16

82

8

85

4

88

2

91

1

94

Minutes

30

97

15

100

7.50

103

3.75

106

1.88

109

0.94

112


Noise exposure has also been associated with temporary hearing loss, decreased perception of noisiness and masking, increased stress, fatigue, disturbance of sleep and decreased concentration and mental performance (Osada, 1988). Noise-induced hearing loss starts in the higher frequencies (3,000 to 6,000 Hz) and slowly develops from chronic exposure to excessive sound. Sound must exert a shearing force on the hair cells lining in order to be perceived, and if the force is too strong, cell damage and cell death can occur (Berger et al., 2003).

How Risks are Reduced:

These materials are primarily designed to absorb noise but they also block or reflect noise to varying degrees. Through the use of specially designed absorption materials, which may be mounted on high gauge steel, aluminum or zinc frames, sound is absorbed when it reaches the noise curtain or absorption material. Noise reduction increases with thickness of the material, especially at frequencies above 500 Hz (Berger, 2003). Absorption materials are designed to reduce sound energy, as opposed to reflecting it, reducing noise exposures for workers and bystanders on both sides of curtains and enclosures.

While there is little published sampling data on these specific products, there are studies indicating that exposure to noise can be significantly reduced through the use of noise curtains and absorption materials. Using noise control techniques will reduce exposure to hazardous levels of noise and reduce environmental or community noise. The extent that they reduce noise exposure is expected to be significant. The extent of the reduction is dependent on the type of material used, the method of noise reduction (absorption versus reflection), the level of noise in the environment, the absorption properties, the proximity to the noise source, and the properties and size of the room or work area.

A study was performed to determine the effectiveness of absorption foams, particularly the SONEX foam. After construction of a plexiglass enclosure with the foam panels installed on the walls and ceiling, sound was introduced at different frequencies to determine how much sound was absorbed by the foam. Researchers found that the foam did not absorb noise at frequencies of 125 and 250 hertz. However, the foam effectively reduced noise levels by 18-28 dBA at frequencies between 500 and 4,000 hertz (Wertel, 2000).

Industrial hygienists use sound level meters or noise dosimeters to determine noise levels and recommend the use of quieter techniques to prevent hearing loss and reduce the risk of accidents. Proper maintenance and retrofitting existing equipment can decrease excess sound as well (Suter, 2002).

One manufacturer, Industrial Noise Control, states that its Noise Control Curtains can obtain a transmission loss of 21-30 dBA.

Another firm, dB Engineering, claims that its noise curtains can obtain a transmission loss of 29-31 dBA.

Effects on Productivity:

Lower noise levels are expected to reduce stress and fatigue, and increase the concentration and mental performance of workers. Improved worker health, comfort and concentration may lead to greater productivity. Reduced sound levels can also lower the risk of accidents as communication among workers is easier and more effective. The number of noise-related complaints received, particularly from the impacted community may be reduced, thereby increasing productivity.

Additional Considerations:

The use of diesel and especially gas-powered equipment poses the risk of carbon monoxide exposure, especially in enclosures and areas where airflow is reduced. Steps to control exposure are important because the gas is invisible, odorless and tasteless. Poisoning by carbon monoxide can occur quickly indoors or in enclosures, but working outdoors does not ensure operators won’t be overcome. Small, inexpensive personal monitors should be worn by the operator to warn of unacceptable exposures. Equipment should not be left idling to cut down on carbon monoxide and to conserve fuel.

As is the case with any construction equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.

Contributors:

Andrew Kingston, Michael R. Cooper, Bruce Lippy - The Lippy Group, LLC

Hazards Addressed:

  • Heavy Equipment
    • Operate stationary equipment

Availability

dB Engineering Noise Control
To obtain information, visit www.noisecurtains.com or contact 1-800-666-6473

Kinetics Noise Control
To obtain information, visit http://kineticsnoise.com or contact 1-877-457-2695

Industrial Noise Control
To obtain information, visit http://www.industrialnoisecontrol.com or contact 1-800-954-1998

SONEX Noise Control
To obtain information, visit http://www.sonex-online.com or contact 1-360-221-7818

Singer Saftey Noise Control
To obtain information, visit http://www.singersafety.com or contact 1-888-739-1045

Return on Investment

To calculate the return on investment (ROI) for your specific application, please visit our Return on Investment Calculator. While a specific ROI example has not been developed for this particular solution, the ROI Calculator provides a useful tool and guidance on how to generate your own on investment analysis.