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Preparation:
A home-made drum with a balloon
membrane as visual aid.
Material:
Cassette-recorder, microphone,
several old loudspeakers, tools, scissors, tape with different sounds (for
example thunder, rain, storm...), different magnets, small items made of iron
(for example paper clips), Orff instruments, a box for storing the parts of
the loudspeakers.
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Steps:
The children listen to the sounds
on the tape and think about how the sounds come out of the tape-recorder.
The children examine the old
loudspeakers: They take them apart and discover the membrane, the magnet, the
centering spider and the coil of copper wire.
Experiment 1: The children build a drum. They use a balloon
and see how its skin vibrates when it is being pulled and how it makes a
sound this is how the membrane vibrates in the loudspeaker and makes
sounds!
Experiment 2: The children play with the magnets. They look
for things that they attract or repel.
Experiment 3: The children cut out the centring spider and
see the coil made of copper wire. They discover that it can be rolled up and
unwound and that it is made of metal.
The individual parts of the
loudspeaker are collected in a box for a Technology Exposition".
The children try to imitate
sounds from nature by playing Orff instruments and they record those on a
tape.
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Technical Explanation:
The casing serves as a soundbox for the loudspeaker.
Parts of loudspeaker are: a membrane, a big magnet
and a copper wire coil that is coiled around a so-called swinging coil base. An
electric current flows through the coil and since it is surrounded by a big
magnet (which is also called cup magnet" because it is hollow in the
middle and therefore looks like a cup), it keeps on moving between the poles.
This motion also makes the membrane move: This produces sounds that sound
different depending on the electric impluse.
The ringed fabric is the
centring spider", which makes the coil stay in the exact middle of the
magnetic field.
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