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The
exhibit plays a note on a flute as a strobe clicks away. On a
nearby screen, the strobe makes a shadow of the flute. Near the
flute shadow, the shadow of the air stream tumbling into and out
of the flute orifice can be seen in slow motion. A Schlieren projection
system driven by the strobe makes this shadow picture of the air
oscillating in and out of the flute. The visitor can adjust the
strobe flash frequency. When the flash frequency exactly matches
that of the flute sound, the shadow of the air motion appears
to stand still. As the frequency of the strobe is changed away
from this frequency, the rhythmic air motion appears to speed
up.
This exhibit allows visitors to see the air as it spills rhythmically
across the orifice of a flute. They can also put their fingers
into or near the flute orifice and see the shadow of their finger
and its affect on the air flow at the same time that they hear
the effect of their finger on the sound. The flute uses the resonant
motion of air in a tube to amplify sound waves.
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