Casio vl 1 service manual

Page 2

2. THE ABC's OF SOUND

2-1. What is the sound?

A gong is a good example of how sound occurs

(see Fig. 2-1).

When a gong is struck, the metal first bulges outward,
compressing the air molecules nearby and giving them
energy, The molecules compressed by the gang bump
against others and set in motion a wave which travels
through the air. When these waves reach the eardrum,
we recognize it as a sound.

Instruments that use electricity to magnify their
sound waves are called electric musical instruments.
An electric guitar is a good example. Instruments
whose sound waves originate with electrical impulses;
as with a synthesizer, are called electronic musical
instruments.

2-2. The three basic properties of sound and the envelope

The three basic properties of any pure sound are its
pitch, its timbre and its volume. Its other important
characteristic is the envelope. which shows how the
amplitude changes between the time of attack and its
release.

When a sounds vibrations are converted into electron-

ic signals, the curve can be read from an oscilloscope

(Fig. 22).

Sometimes the length of a sound is considered one
of its basic properties as well

(A) PITCH
Pitch is simply the rate at which vibrations are
produced, This is called frequency. In the Fig. 2-3,
the frequency of wave b, is double that of wave a.
When the frequency doubles, the sound raises one
octave in pitch
Notes expressed in lrequency (No. of Hz) raise an
octave as the frequency doubles.

(Bi VOLUME
Volume depends upon the strength. or amplitude,
of the vibrations producing the sound. If the
vibration IS strong, with a wide wave, the sound
will be loud. If the vibration is gentle, with a
narrow wave, the sound will be solt. (Fig 24),

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