Direct the air jet toward the holes
of the
rotating disk. Different rows of holes produce notes of different
frequencies.
Siren disk demonstrates how pitch and
intervals
are related to vibration frequency. One can show that changing
the
motor speed changes the pitch (frequency) but not the intervals
(frequency
ratios).
NOTES
Set motor frequency to 11 Hz.
There are two siren disks with
chucks.
The smaller one has concentric rings of 5, 10, 15, ... 45 holes for the
harmonic overtone series. The larger one has rings of 24, 27, 30,
32, 36, 40, 45, 48 holes and produces one octave of a major scale.
There is also a nozzle with two outlets for playing chords.
One can play tunes like "Finlandia,"
"No Place
Like Home," etc., confined to one octave above tonic, with no
accidentals.
