THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

540 18. Music and Musical InstrumentsFigure 18.26. The modern flute.corresponding to the musical scale, either by the fingers directly or through actuationof keys. This system of keys and connecting shafts and levels constitutea mechanism that actuates valves that are basically disks that cover fingerholes.Springs are utilized to keep the valves in the unactuated position, which may beeither open or closed. This system renders it possible to open or close fingerholesthat are too far apart or are too large to be stopped by the fingers alone.The sound of the flute is generated in this manner: In Figure 18.27 an air streamfrom the lips impinges upon the embouchure of the flute. Resonant frequencies aregenerated by the air stream slipping back and forth between entering the flute bodyand flowing past the embouchure. A stream of air enters the blowhole (ϑ = 0 ◦ ),causing a pressure to build up to the extent that it stops air from entering (ϑ = 90 ◦ ).The excess pressure (ϑ = 180 ◦ ) then forces the air out of the blowhole until it stopsleaving the blowhole (ϑ = 270 ◦ ). The cycle then repeats itself.The piccolo can be considered a smaller version of the flute that operates oneoctave higher. The operational principle of the piccolo is fundamentally the sameFigure 18.27. The action of the flute: the directions of the arrows indicate airflow direction.