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# Sound Transmission through Massive Walls or Floors

## Sound transmission and attenuation in building elements like massive concrete walls or floors.

The sound transmission through a massive wall or floor depends primarily on the mass of the construction.

Mean attenuation through a massive construction is indicated in the diagram below:

Note! - more mass - more attenuation!

The attenuation for a specific frequency can be calculated by adding the value in the table below to the mean value indicated in the chart above.

Frequency
(Hz)
631252505001000200040008000
Attenuation Correction
(dB)
-13 -9 -5 -1 3 7 11 15

Note! - higher frequency - more attenuation!

### Example - A Concrete Floor and Sound Attenuation

The mass m of a concrete floor with density 2300 kg/m3 and thickness 0.2 m can be calculated as

m = (2300 kg/m3) (0.2 m)

= 460 kg/m2

From the chart above the mean sound attenuation for the floor can be estimated to

52 db

The attenuation dL at 250 Hz can be calculated as

dL = (52 db) + (- 5 dB)

= 47 dB

The attenuation at 2000 Hz can be calculated as

dL = (52 db) + (7 dB)

= 59 dB

### Sound Transmission Loss - or Attenuation - for some typical Building Elements

Building ElementSound Transmission Loss
Attenuation
- STC Rating1) -
(dB)
Privacy
230 mm brickwork, plastered both sides 55 Shouting not audible
Standard 38- by 89-mm (nominal 2- by 4-in) wood studs with resilient channels nailed horizontally to both sides with 20-mm (5/8-in) gypsum wallboard screwed to channels on each side 50 Shouting barely audible
230 mm brickwork, plastered one side 48
115 mm brickwork, plastered both sides 47
100 mm timber studs, plasterboard both sides, quilt in cavity 46 Loud speech barely audible
6 mm double glazing, 100 mm air gap 44
75 mm clinker concrete block, plastered both sides 44
115 mm brickwork, plastered one side 43
Two layers of 20-mm (5/8-in) gypsum wallboard nailed to both sides of standard 38- by 89-mm (nominal 2- by 4-in) studs 40 Loud speech audible but not intelligible
75 mm timber suds, plasterboard both sides 36 Loud speech audible and fairly understandable
6 mm single glazing 29 Normal speech audible but not intelligible
one layer plasterboard 25 Normal speech easily understood

1) STC - Sound transmission class is the USA rating used to characterize airborne noise insulation. A wall system with higher STC rating is more effective in preventing the transmission of sound.

## Related Topics

• Acoustics - Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.
• Noise and Attenuation - Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.

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