The tonal noise synth is made up of a LFSR digital white noise source
and 2 filters in series. Both filters are state variable bandpass types,
one with a Q of 1.0, the other with a high Q which changes depending on
pitch. Both filters receive the same data for Fc.
The sample rate of 806 kHz was chosen for headroom for the filters. This provides a very linear response to Fc value for the frequency range used as well satisfying the requirement multipole recursive filters have of keeping Fc below 1/6 the sample rate.
This is a work in progress. The synth is functional, but a better method of compensation for amplitude needs to be developed. Currently it's just linear. It helps, but there is still a large disparity in the amplitude of high pitches and low pitches. It may be more effective to work with Q compensation rather than linear attenuation of the output of the filter.
|The synth can be heard in Eleventy Twelve. It's the airy whistle sound.|