Soundboard Envelope

The soundboard excitation is generated by noise multiplied by two exponential envelopes. In testing the Soundboard class, I discovered that a noteOn event created an endlessly sustained note until the noteOff event. This is shown in Fig. 4. Not only was this behaviour different from the SynthBuilder subpatch, it does not make physical sense. The starting amplitude also differed from the SynthBuilder recording. I addressed this by adding missing scaling factors and the pedalPresenceFactor control parameter. I also adjusted the behaviour of the pedal envelope to match the logic in the SynthBuilder C note filter, BrandNewThump.c. With these changes, the envelope begins to decay on noteOn and the decay rate is increased on noteOff. Now the Soundboard behaves as expected, as shown in Fig. 5

Figure 4: Soundboard impulse for a sustained A0 prior to fix.

Figure 5: Soundboard impulse for a sustained A0. Top: SynthBuilder recording, bottom: STK implementation.