Granulation

Granular Synthesis is the segmentation of an audio file through the application of a window function. The anatomy of a grain determines the sonic signature of a granular stream. To imbue the sound file with other parameters of the current weather, wave and wind information are mapped to the granular windowing or control parameters of the granulator.

The control data is drawn from a NOAA file that polls the weather conditions each hour. This means that the control parameters provide roughly 8000 values, while the audio file contained 10-minute segments. To align the data, the read head of the granulator is advanced in increments of six so that the window function for each single control value is applied to an audio sample where the temporally corresponding data is at the apex of the window function. See image below

Mapping Data to Granular Controls

The Data Mapping for the granulation uses the Dominant Wave Period (DPD), Average Wave Period (APD), Wave Height (WVHT) and the Wind Direction (WDIR). The Tgrains unit generator is employed as a starting point. The window function is a constant Hann window. In order to poll multiple simultaneous streams of control information each parameter was first converted to an audio file then stepped through according to the trigger rate. The trigger rate is controlled by the user with the mouse x position. The mapping is the control data is as follows.

1.   Grain Amplitude = WVHT

2.   Grain Stereo Position = WDIR

3.   Grain Duration = Random value between APD and DPD.