Plucked String Model

In this string simulator, there is a loop of delay containing

$$N = 2L/X= f_s/f_1$$   samples$$$$

where $f_1$ is the desired pitch of the string and $L$ is the physical length of the string.

• What is the impulse response of this structure?

• Define an input $x(n)$ and an output $y(n)$.