Casio CZ-5000 - Page 20

Every
day,
we
hear
a
great
variety
of
sounds.
Voices,
the
noise
of
car
engines,
doors
opening
and
closing,
footsteps,
rain
...
and
music.
In
other
words,
we
live
our
lives
surrounded
by
sound.
We
can’t
see
sound,
so how can we describe it?
Physics
tells
us
that
“Sound
is
vibration”.
Taking
the
sound
of
a
bell
as
an
example,
we
will
try
to
pursue
the
basics
of
sound
as
it
is
produced
and
as
it
is
heard.
When
kinetic
(motive)
energy
is
applied
to
a
bell
with
a
bel!
hammer
as
shown
in
figure
1,
a
‘‘deformation”’
of
the
bell
occurs
causing
energy
to
work
trying
to
restore
the
bell
to
its
original
state.
A
periodic
repetition
of
deformation
and
restoration
commences.
This
is
called
vibration.
This
vibration
causes
pressure
changes
in
the
air.
These
are
called
compressional
waves.
They
are
similar
to
the
ripples
that
occurs
when
a
stone
is
thrown
into
water.
These
compressional
waves
are
transmitted
to
the
human
ear
where
thev
cause
the
eardrum
to
vibrate.
These
vibrations
are
picked
up
by
nerves
so
we
hear
them
as
“sound”’.
If
the
vibrating
body
differs,
so
will
the
vibrations,
meaning
that
we
also
hear
a
different
kind
of
sound.
Outer
space,
where
there
ts
no
air,
is
a
world
altogether without sound.
| paca Vibrational (Eardrum) |
|
ere
|
—-
|
YD)YINNNYMDIGL
———-
Sounas
vibration
oF
the
a
Compressiona!l
waves
|
(fig. 1) i
“74 Wave Forms
—
Seeing
Sounds
With
Our
Eyes
———
As
explained
above,
sounds
cannot
actually
be
seen
since
they
are
vibrations
of
the
air.
However,
you
will
often
hear
expressions
such
as
“the
wave
form
is
different”
or
“this
is
almost
a
pure
sine
wave”
concerning
sounds.
What
is
meant
by
‘‘sound
waves’’?
Condensed |
Pressure
changes
=
(high
atmospheric
pressure)
™
yy
a)
Ey
-
dense
|
dense
i
dense
ite
Rarefied
2
!
ow
atmospheric
=
1
cycle
—=
non-dense non-dense
pressure}
Let’s
consider
the
mechanism
of
a
microphone
which
is
used
as
a
means
for
picking
up
sound.
A
microphone
converts
sound
into
electrical
signals
which
can
be
then
transmitted
to
an
amplifier
and
speakers.
As
shown
in
the
illustration,
these
electrical
signals
are
simple
conversions
of
the
vibrations
of
the
air
(the
changes
in
atmospheric
pressure)
into
electrical
G
and
©.
When
these
changes
are
presented
graphically,
they
can
be
interpreted
as
‘“‘wave
and
displays
then
as
waveforms
on
a
television
screen.
If
we
use
this
kind
of
a
device,
we
can
see
sounds
with
our
own
eyes.
What
we
see
are
‘‘waveforms’’.
These
waveforms
differ
greatly
according
to
the
sound
and
have
various
charac-
teristics.
These
points
will
be
explained
later
on
in
the
Appendix.
If
be
lex
We nc
talkin:
and Ic
variet®
“volu:
are de
. |.
las
When
is loc
Wher
diffe:
wave