String Interface

Referring to Fig. 4.18 showing a basic string simulator, it is possible to eliminate the explicit comb-filtering corresponding to the hammer striking position. The uniform spacing of the force pulses in the excitation signal $f(t)$ is the same as the delay needed for the striking-position comb filter. As a result, the physical force-injection signal $f(t)$ can be replaced by the comb-filtered version $g(t) = f(t) - f(t-\tau)$, where $\tau$ is the travel time from the striking point to the agraffe and back. The comb filtering can be applied to the excitation table prior to the shaping filter(s), or the shaping filter(s) can be designed to convert the excitation table directly into $g(t)$ rather than $f(t)$. In either case, the final excitation signal $g(t)$ simply drives a single filtered delay loop, as shown in Fig. 5.11.

Figure 5.11: The basic, filtered delay-loop string model.