Agriculture Reference
In-Depth Information
arriving at the wall. The higher the coefficient,
the more absorbent the material. It depends on
the wave's angle of incidence, on the thickness
of the wall and the frequency of the wave.
Results obtained by the ENTPE are presented
in Fig. 17.12 for waves arriving normally on a
partition wall with a thickness of 20 cm. They
are compared with results obtained under the
same conditions for other commonly used
building materials (Fig. 17.13). The microstruc-
ture of hemp provides these materials with
excellent absorption, with coefficients ranging
from 0.4 to 0.9, depending on the frequency
under consideration. The intrinsic qualities of
these materials are underlined further by the
confidence of returning customers, who praise
the acoustic comfort of rooms constructed
from hemp concrete or where the walls have
been lined with a hemp plaster.
It should be noted that the acoustic prop-
erties are also dependent on the quality of the
connections between the different structural
elements (partition wall, floor, door and win-
dow frames, etc…).
1
0.9
0.8
Wall-10cm
0.7
Wall-20cm
0.6
Wall-30cm
0.5
5
0.4
Tile-10cm
0.3
Tile-20cm
0.2
0.1
0
100
1000
Frequency (Hz)
10000
Fig. 17.12.
Coefficient
α
for acoustic absorption for walls and tiles of different thicknesses (10, 20 and 30 cm).
1
0,8
0,6
0,4
0,2
0
100
600
1100
1600
HERTZ
Hemp concrete (24%)
Hemp concrete (33%)
Hemp concrete (35%)
Painted concrete
Bricks
Plyboart
Gypsum
Fig. 17.13.
Coefficient
α
for acoustic absorption in thirds of an octave for different building materials.
