| Application
note # 2 |
Sample
Champion
|
Examples
of reflections on a surface
When
selecting the anechoical part of an Impulse Response, the reflected
wave must be recognized and rejected from the analysis. The
reflected impulses have the same shape of the anechoical
wave, but have been "filtered" by the
surface and have lower amplitudes.
In
every case (and especially when reflected waves are very low),
the localization of the first reflection must be confirmed with
physical arguments:
The
time t between the "anechoical
" impulse and the first
reflection is:
t=(S2-S1)/c
where
S1 is represented in the figure with the red path, S2 with the
green path and c is the sound speed (with Sample Champion
the exact value of c, depending from air temperature,
can be read inside the measurement geometrical setup window).
 Here
are 2 examples of reflections:
The
first is a reflection against an absorbing surface, the second
against a reflective material.
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