Oscillations
and Waves > Instruments > Air Columns
DCS#
3D30.21
RESONANT
FREQUENCIES
OF CONES
APPARATUS
brass phonograph horn
202-07-C
HP audio generator
202-08-G
microphone on a stick
202-06-C
speaker
202-07-F
DESCRIPTION
This cone has resonant
frequencies of
about 200, 400, 600, ... Hz.
p(x,t) = A/x sin kx cos ωt
By
setting the audio generator to
800 Hz,
inserting the microphone on a rod through the narrow end of the cone
and
moving it along the axis, you can see the three internal pressure
nodes,
the increasing amplitude of the antinodes as you move toward the
vertex,
and the approach to a pressure antinode at the vertex of the cone.
Set the
audio generator to the
fundamental
frequency, and pressure increases monotonically as the microphone is
inserted.
