Figure 2.5 A method for producing a sound grain (Dodge & Jerse 1997: 263).
involves multiplying the amplitude of the contents with the amplitude of
may cause some slight convolution to the grain, but as a sonic grain is
so small it is not noticeable.2
If the grain is constantly repeated in a synchronous manner the convolution
will become noticeable. This suggests that the parameters of the envelope
can be changed to alter the spectral composition of the grain and give
extra control over the grain.
There are certain parameters that define an envelope. These are:
Diagram of a simple envelope.
of the envelope determines the entire duration of the grain. Experimentation
has shown that durations of between 10 milliseconds and 50 milliseconds
are the best to work with.3
Obviously this is an extremely short duration, therefore only the most
salient features would be immediately obvious.The duration determines the
distinction of the contents of the grain. Grains with a shorter duration
have a more ambiguous spectrum. This is due to the time-frequency relationship
of sound. The shorter the duration, the less the spectrum is defined. A
short grain duration creates a broader bandwidth making the grain noisier.
This is very useful for creating a larger spread of frequencies. Another
feature of using a short duration is that it is more difficult for the
ear to decode the contents. This allows the composer to deceive the listeners
perception of sound. An isolated grain with a very short duration produces
a kind of buzzing or clicking sound. A longer duration causes less convolution
in the contents of the grain. An isolated grain with a longer duration
sounds more like when a woodblock is tapped on. Different durations become
much more significant when there is more than one grain involved, as discussed
refers to the peak amplitude. It determines the height of the envelope.
This parameter may be applied directly by specifying the amplitude, or
it may be implied indirectly by the other parameters. It is also influenced
by the contents of the grain. The amplitude of the envelope dictates whether
the amplitude of the contents is able to reach full capacity or not. The
envelope amplitude as such, can be worked out as a percentage, 100% being
2.2.5 Decay time
time determines how quickly the envelope drops back to zero amplitude.
Different gradients of release will produce faster or slower cut off times.
The release does not have to be at the same rate as the attack. When working
with synchronous granular synthesis a different release time to the attack
time will impose a different spectrum on the resultant sound. This is caused
by convolution between the envelope and the contents. In an isolated grain
the effect is not really noticeable. In order to percieve the resultant
sound it must be repeated at a continuous rate, which is why it has less
effect on asynchronous granular synthesis.