INTRODUCTION TO SYNTHESIZERS - hol.gr

The essence of sound
In order to fully understand how synthesizers work, we must first understand the physics behind the
phenomena we perceive as "sound". So, what is a sound?
The air surrounding us consists of gas-particles. If you force a number of these particles to move, they will
create a wave traveling from one particle through the next, in all directions away from the source. It's just like
when you throw a stone into a pond - the water particles will create ripples or waves, moving away from the
center.
Sound-waves are also initiated from a source, like a car engine, a slamming door or a finger plucking a guitar
string. These ripples, or vibrations travel through the air and reach our ears, where they will set our eardrums
into motion. This motion is in turn perceived by our brains and interpreted as a "sound".
Of course there are many different sounds. Any non-deaf person can hear the difference between a barking dog
and a singing voice. But how can we do that?
A sound-wave has three main properties. These properties are:
• timbre
• pitch
• volume
Timbre
The tonal color or timbre is probably the most important factor for the character of a sound.
Let's illustrate it with an example: say that you play and hold a single note on the accordion. Most of us will
instantly recognize the sound as being an accordion.
If you now play the same note on the flute, you will probably hear the difference. Even if both instruments play
the very same note and at the same volume, you can easily distinguish between the two sounds. That is
because they have different timbres - different sound colors.
We already mentioned that the sound is just a vibration in the air. Now, if you make this vibration visible, for
instance by using an instrument called an oscilloscope, you will see that different timbres have different
waveforms. This may sound very technical indeed, but the word "waveform" is so commonly used in synthesizer
related text, that you should be familiar with it. We can just say that different waveforms simply "sound"
different.
So, what does such a sound-wave look like? Let's look at an example!
(Click on the loudspeaker icon to listen to the waves!)
A simple sound-wave
This is a very simple waveform, called a sawtooth wave. You can probably see why it is called that: the wave
has a repeating "sawtooth-like" pattern. This pattern is the timbre of the waveform. Generally you can say, that
the more "sharp" edges a waveform has, the more "harsh" it sounds.
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