Sound & Hearing

Air Reed

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.