PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Sound Absorption of Brazilian wooden panels and their use asBuilding ComponentsRodrigo SCOCZYNSKI RIBEIRO1; Márcio Henrique AVELAR GOMES2; Rosemara Santos Deniz
AMARILLA3, Fernando Jun Hattori TERASHIMA4, Luis Henrique SANTANA5, Rodrigo Eduardo
CATAI6, Adalberto MATOSKI7
1 ,2,3,5,6,74

Federal University of Technology, Brazil

Pontifícia Universidade Católica do Paraná

ABSTRACTIn this study, the normal incidence sound absorption coefficients were obtained from three types of woodenpanels (with different thicknesses of them): Oriented Strand Boards (OSB); Medium Density Fiberboards(MDF) and Wood-wool cement boards (WWCB). The panels were manufactured according industrial
processes, using Brazilian woods and reaching lower levels of CO2 eq emissions in its Life-cycle Assessment
when compared to the conventional building techniques for vertical sealings in Brazil. The panels are used in
the furniture market, but the results show that the material can be used in order to improve the soundabsorption of a room as an acoustic panel, a ceiling or other type of building element.
Keywords: Wooden panels, sound absorption.

1. INTRODUCTION
The built environment, which includes buildings and infrastructure, involves large quantities ofmaterial and energy consumption and is an essential component of the economic and socialdevelopment (17). The construction industry is responsible for considerable natural resources
diminution and generates a substantial amount of wastes (16).
The reduction of CO 2 emissions in the construction sector is a key element for the achievement ofenergy conservation and emission-reduction goals worldwide (27).
Life cycle assessment (LCA) is a technique regulated by ISO 14040 (19) and ISO 14044 (20) thatcompiles the inputs and outputs of a product or service quantifying its carbon footprint . The LCA takes
a comprehensive and systemic approach to environmental evaluation, and because of that, the interest
in incorporating LCA methods into building construction is increasing, supporting decisions forselection of environmentally preferable products, as well as for evalua tion and optimization ofconstruction processes (1,7). The life cycle impact assessment (LCIA) is the first step of the LCAcalculation process and the output of it is the carbon footprint.
According to Caro (8) “carbon footprint is an easy-to-apply tool for monitoring andquantifying greenhouse gas emissions, as well as checking mitigation/reduction programs at different
scale. It is able to capture the total amount of greenhouse gas emissions directly and indirectly caused
by a country, an activity or accumulated over the life stages of a product”. Its unity is the CO2 eq(carbon dioxide equivalent).
Huang et al. (17) described that the three main pivotal opportunities to reduce the carbon emissionsof a construction sector are the use of low embodied carbon material and services at life cycle
1

rodrigosribeiro@utfpr.edu.br/rsco.ribeiro@gmail.com

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perspective; the energy efficiency increasing of construction machines and the promotion of therenewable energy use.
In Brazilian typical buildings, Evangelista et al. (13) described the concrete, steel and ceramic tiles
as the highest environmental impact materials, with repercussions for the structure, masonry andcoating subsystems. Crippa et al. (9) predicted a carbon footprint about 335 kg CO 2 eq/m³ (50.3 kg
CO2 eq/0.15m of thickness) for a sealing built with clay brick and plaster undercoat and about 302 kg
CO2 eq/m³ (45.3 kg CO 2 eq/0.15m of thickness) for a sealing built with concrete block and plaster
undercoat. These sealing systems are commonly built in Brazilian buildings.
Estokova et al. (12) related that vertical bearing walls and partition walls represented 28.3% of thecarbon footprint estimated for twenty conventional masonry houses built in central Europe. It is only
behind the foundations, which had 57.8% of representative in the carbon footprint.
This research aims to analyze the sound absorption properties of some wood panels, made from
Brazilian woods, suggesting their use as building elements in Brazilian construction sector as acousticpanels, floors, ceilings or coating subsystems in order to improve the sound absorption of a room.
Three different types of wooden panels will be tested in order to achieve their sound abso rption
coefficients: Oriented Strand Boards (OSB), Medium Density Fiberboards (MDF) and Wood Wool
Cement Boards (WWCB). By nature, wood is made of carbon that is captured from the atmosphere
during tree growth. The effects of substitution and sequestration are why the carbon impact of wood
products is favorable (5).
Their carbon footprint (cradle-to-gate) is shown in Table 01. The presented value per m³ for
WWCB was calculated considering a thickness of 25mm (4.85 KgCO 2eq/0.025m).
Table 1 – LCIA of different panels
Type of panel

Quantity ofmaterial, m³

Kg CO2 eq

SourceOSB

1.00

127.0(15)

MDF

1.00

199.0(24)

WWCB

1.00

194.0(30)

Aiming in the acoustical properties, it is well known that the reverberation time (RT) in a room canbe detrimental to speech intelligibility (21). The RT can be increased or decreased according to thebuilding materials absorption properties. From the materials perspective, sound absorbing porous
materials perform an important role in the room acoustics (11), and the reverberation time can bereached by adding or suppressing absorption areas, as the descriptions of the pioneering work ofSabine (26), who developed a model based on the statistical theory of sound field – it considers thesame density of sound energy at any point of a room, with the same probability of incidence at anydirections. This model could be used in a room with known volume and sound absorption coefficients.
Different models were developed through the years, improving the Sabine’s model, as shown in
the research of Nowoświat et al. (22). The sound absorbing properties of the material is expressed by
the sound absorption coefficient α as a function of a sound frequency band. The “α” values ranges from0 to 1.00 referring to a total reflection situation to total absorption situation (11).

2. MATERIALS AND METHODSThe OSB is a multi-layer panel made from strands, with strips of wood with a length greater than
50mm and a thickness less than 2mm, glued with a synthetic resin. The strands in the outer layers areparallel and aligned to the length of the panel. The strands in the center layer of layers can be randomly
oriented (or aligned) generally perpendicular to the outer layers ( 14). At most, Brazilian OSB are
manufactured with pine wood particles obtained from dedicated forests mainly from Pinus elliottii andPinus taeda (loblolly pine) (15). These species are not native and reforestation programs provide them.
Ferro et al. (15) discussed the environmental aspects of the OSB production through its Life -CycleAssessment.
According to Piekarski et al. (24), the MDF “is an engineered wood product, made by breaking
down softwood into wood fibers and combining them with wax and resin to form panels by applying
high temperature and pressure”. The same research gives its Life-Cycle Assessment according to theBrazilian way of production. The MDF is primarily used as furniture, in joinery industry and in2960

interior architecture design.
The Brazilian WWCB is also produced from dedicated forests (as the OSB and the MDF). As thedescribed by de la Grée GD et al. (10), the WWCB is produced by the following sequence: the stored
wood logs are cut into in small blocks (about 25cm in length), so that shredded to wood-wool in superfine straw (width≤1mm), fine straw (1-3mm in width) or thick straw (width ≥ 3mm). Then, thewood-wool is dipped in a solution to accelerate the compatibility at wood -wool-cement paste interface
and are afterwards pressed do decrease water content. The wet wood wool moisture content withcement powder are fed into a continuous mixer. After that, the mixture is transported to a distribution
machine which spreads the mixture in layers into the molds which will be pressured by a hydraulicpress. After the setting of cement, the boards are taken from the molds for further curing, and a processof storage starts. Finally, the plates can be painted, stacked and placked. An example of the LCA for aWWCB is described in Thinkstep et al. (30).
It was tested different thickness of the panels, as shown in Table 02. 100 samples were measure
which means that 10 samples were set for each type of panels.
Table 2 – List of samples
Density
Type of panel

Thickness, mm

approximately,
g/cm3

Number ofHow issamples

referenced

Indicatedletter inFigure 1

MDF

9.00

0.55

10

MDF – 9mm

c

MDF

12.00

0.55

10

MDF – 12mm

bMDF

15.00

0.55

10

MDF – 15mm

aOSB

8.00

0,52

10

OSB – 8mm

fOSB

12.00

0,5210OSB – 12mm

eOSB

25.00

0,5210OSB – 25mm

d17.000.40

1025.00

0.40

1050.00

0.40

1025.00

0.4610WWCB withthick straws
WWCB withthick straws
WWCB withthick straws
WWCB withsuper fine

WWCB – TKS
17mm
WWCB – TKS
25mm
WWCB – TKS
50mm
WWCB – SFSstraws

25mm

jigh

The Figure 1 shows the different types of panels tested in this research.

Figure 1 – Samples
An impedance tube (manufactured by SCS ControlSys, model 9020 B/K, with 98±2mm diameter)2961

was used and the measurements were performed with the Transfer Function Method (28), providing
the normal incidence sound absorption coefficient (αN). A noise generator – Brüel & Kjær Type
3160-A-042 (6 channels) – and two array microphones with preamplifiers - Brüel & Kjær Type 4935 –controlled by a PULSE TM completed the instrument set for measurements. The guidelines of ASTM
C384-04 (4) and ISO 10534–2 (18) were applied.
After the measurements (10 samples per type of panel), a confidence interval (95% confidencelevel) was established with a t-distribution for each frequency between 100Hz and 2000Hz. A new
average was calculated with the values into the confidence interval,
All the graphs and calculations were performed in the “R” software (25).
The Noise Reduction Coefficient was calculated according ASTM C423-17 (5), defined as “Roundthe average of the sound absorption coefficients for 250, 500, 1000, and 2000 Hz to the nearest
multiple of 0.05”.

3. RESULTS AND DISCUSSIONSThe Figures 2 to 6 present de normal incidence sound absorption coefficient for each type of panel.
The plotted curves consider the new averages after the confidences intervals treatments.

Figure 2 – αN for OSB – 8mm and OSB – 12mm

Figure 3 – α N for OSB – 25mm and MDF – 9mm2962

Figure 4 – αN for MDF – 12mm and MDF – 15mm

Figure 5 – α N for WWCB – TKS 17mm and WWCB – TKS 25mm

Figure 6 – αN for WWCB – SFS 25mm and WWCB – TKS 50mm
Figures 7,8 and 9 show the sound absorption coefficients for different thicknesses of the OSB, MDF

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and WWCB, respectively.

Figure 7– α N for different thicknesses of OSB

Figure 8– αN for different thicknesses of MDF

Figure 9– αN for different thicknesses of WWCB
Table 03 shows the NRC of the panels.

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Table 3 – NRC of the panels
TypeNRC

MDF

MDF

MDF

OSB

OSB

OSB

9mm

12mm

15mm

8mm

12mm

25mm

0.10

0.10

0.10

0.100.100.15

WWCB

WWCB

WWCB

WWCB

TKS

TKS

TKS

SFS

17mm

25mm

50mm

25mm

0.20

0.25

0.45

0.30

Palomar et al. (23) measured the normal incidence sound absorption coefficient for different
compositions of lime-cement mortar obtaining the maximum value of 0.113 for a mortar with 1.59
g/cm³ of density, 96±2mm diameter and 40±2mm thick. If compared to the NRC values in Table 3 it
could be concluded that the wood panels have better sound absorption coefficients than Brazilian
commonly coating system.
The WWCB performed the best values for sound absorption and could be strongly recommended toacoustic treatments in order to decrease reverberation times. The WWCP – TKS 50mm has a αN about
0.80 at 1kHz, which is a considerable value. The WWCB – TKS 25mm got higher coefficients thanWWCB – SFS 25mm for frequencies above 450Hz, which means that the thick straws provide betterabsorption than the super fine straws. The highest α N for MDF panels at low-frequency range is theMDF – 9mm (thinnest one). For the OSB, the highest values are those measured for the thickest one(OSB – 25mm).
Comparing the measured values of WWCB – SFS 25mm with other α N values for a similar material(25 mm thick WWCB with 1.0 mm strand width and density of 0.448 g/cm3 ) from the research ofBotterman et al. (6) a similarity between the curves can be observed. The same occurs with the MDF –9mm compared with the results of a 9mm thick MDF described by Wassilieff (31). For the OSB,
comparing the measured results with those related by Smardzewski et al. (29) for an OSB with 17.5mm
thick it could be noted that the plotted curve has the same design, but different values.

4. CONCLUSION
The study presented the normal incidence sound absorption coefficients obtained from three types
of wooden panels (with different thicknesses of them): Oriented Strand Boards (OSB), Medium
Density Fiberboards (MDF) and Wood-wool cement boards (WWCB). The panels described in thisresearch can be used as ceilings, floors or part of internal vertical sealings instead of plaster orlime-cement mortar, which are widely used in Brazilian buildings. The OSB and the WWCP can also
be used as a partition or façade wall in light steel framing or wood framing construction techniques. In
both situations the levels of carbon footprint of buildings should be decreased because their lower
level of carbon footprint (described in Table 1) when compared to Brazilian typical construction
materials. Also, they have higher sound absorption coefficients than the lime-cement mortar, and they
can be used in order to improve the acoustic conditions of a room.

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