Owner`s manual

CHAPTER 3 -
13
CHAPTER 3 -
The Craft of audio Synthesis
3.2.1.1
Amplitude:
what’s the diameter of this imaginary circle?
Amplitude: what’s the diameter of this imaginary circle? Amplitude:
3.2.1.2
Frequency:
how fast is it rotating?
3.2.1.3
Phase:
when does it start a new cycle?
3.2.2
Complex Attributes
Most of the activity that reaches our ears every day is far
more complex than just a sine wave. Banging on a garbage
can creates a
much
more complicated sort of vibration than
tapping a tuning fork.
But any kind of motion that
isn’t
a sine wave can still be
isn’t a sine wave can still be isn’t
analyzed as a collection of sine waves. This is called
Fourier
analysis,
after the man who discovered that it was possible,
and proved – mathematically – that it always worked.
This goes both ways: any complex signal can also be
constructed
from a collection of sine waves with the
constructed from a collection of sine waves with the constructed
appropriate attributes: amplitude, frequency, and phase
relationships.
In fact,
any kind of motion
– any repeating pattern of the sort
that we are interested in here as “sound waves” - can be
examined and analyzed under two different headings:
3.2.2.1
Waveshape,
and Time-Domain Attributes
Any repeating motion can be diagrammed in a graph where the horizontal axis is a period
of time and the vertical one is the motion itself, back and forth. This is
the time-domain
view of a signal:
3.2.2.2
Spectrum,
and Frequency-Domain Attributes
Instead of looking at a signal as something in motion through a period of time, we can look
at the collection of sine-wave components of the signal. In such graphs, the horizontal axis
is a frequency range (instead of a time period), and we indicate each spectrum component
with a single vertical line in the graph. The height of the line indicates the strength of the
component at that frequency. This is the
frequency-domain
, or spectral-domain, view of a
signal.
It is the distribution and relative strength of spectral components that we experience as
the tone-color of a sound or sounds. “Bright”, “dull”, “sharp”, “tinny”, “heavy”, and so on
– these are all descriptive words for the spectral attributes of sounds.
A complex signal...
can be made of simple ones like this...
...and this...
...and a pinch of this
...and a dash of that.