Rattle and roar
Rattling trucks, roaring jets, squeaking chalk, and creaking doors don’t
make music. They make sounds we don’t want to hear. These unwanted
sounds are called noise.
Noise is hard to stop. Like other sounds, it travels through air and
through solid things—even walls. And it bounces off floors, ceilings,
or any smooth, hard surface. This makes noisy places even noisier!
But some materials actually .\”soak up” noise. They absorb sound waves
and keep them from traveling. These materials are called insulators (IHN
suh [lay]{.smallcaps} tuhrz) because they are sound-stoppers.
Inside a building, rugs and curtains soak up sound. The soft threads and
tiny air
Noisy airplane engines don’t bother this airport worker. He wears
insulated earmuffs that soak up the sound.
spaces in the material help trap the vibrations. Special ceiling tile
can trap sound vibrations, too. The tile is full of tiny holes, like a
sponge. When sound waves strike the tile, they bounce around inside the
holes until they get weaker and die away.
Walls filled with insulators absorb sound in the same way. A thick,
spongy layer inside the wall traps vibrations and keeps most of the
sound from passing through.
People who work with airplanes and other heavy machines can’t use rugs,
curtains, or special walls and ceilings to soak up the sound—so they
wear their insulators! Special helmets and earmuffs cover their ears
while they are working. The sound-absorbing material shuts out most of
the noise that could bother them or hurt their ears.
