Determination of the Impedance of Vegetated Roofs with a Double- Layer Miki Model
Invited paper
Eindhoven University of Technology
Tuesday 2 june, 2015, 16:40 - 17:00
0.8 Rome (118)
Abstract:
Vegetated roof systems on the top of buildings can act as absorbers for
traffic noise
mitigation. Recent research explains the properties of vegetated roofs
that are
important for their sound absorptive and scattering properties. Although
it has been
identified that the substratum is the major contributor to the acoustic
absorption of a
vegetated roof, coverage of this substratum by plants may have a
significant effect on
the acoustic absorption. Short-range acoustic propagation experiments
have previously
been used for in-situ measurements to determine the acoustic impedance
of surfaces as
forest floors, grasslands, and gravel. However, it is still less
practical to estimate
the impedance of a non-locally reacting layer of leaves on substratum
using the
proposed method. The Miki model provides a satisfactory prediction of
the fundamental
acoustic properties of soils, plants, and their combinations with the
advantage of
computational simplicity. Here, the double-layer Miki model is examined
based on the
short-range acoustic propagation method over substratum (with and
without layer of
leaves) in the laboratory, and considered through in-situ outdoor
measurements over
green roofs. In addition, the application of the double-layer Miki model
on the
prediction of the non-locally reacting surface impedance is evaluated by
a comparison
with other impedance models.