The experiment itself is quite simple. We let
the computer play a single note for some minutes.
For this purpose the free ‘Audacity’ digital audio
editor may be used (available for free download at
http://audacity.sourceforge.net/). Then one should
place a funnel above the loudspeaker and measure
the sound level: first, near the lower edge and then
near the upper one (figure 1). This operation should
be reiterated for every funnel. Then, a graph of the
sound amplification Lp as a function of the ratio of
log (S )
S
1
2
(or, for round edges log ( ) R
R
1
2
) should be built
and equation (12b) (or (12c) correspondingly) fitted.
(c) A small loudspeaker connected to a computer.
The area of the loudspeaker should be
of the same order of magnitude as the funnels’
lower edges.