Answer: 384
========================================================
Step-by-step explanation:
The equation is in the form
y = Asin(B(t - C)) + D
where in this case,
The value of B is the only value that affects the period T
T = 2pi/B
T = (2pi)/(512pi)
T = 1/256
Each cycle is 1/256 of a second.
The frequency f is the reciprocal of the period
f = 1/T
f = 1/(1/256)
f = 256
The frequency is the number of cycles per second. In this case, this sound wave has 256 cycles per second. Often you'll see the unit "hertz" used to represent "cycles per second". So the frequency is 256 hertz.
The duration from t = 2 to t = 3.5 seconds is 3.5-2 = 1.5 seconds
Therefore, 1.5*256 = 384 cycles will occur between t = 2 and t = 3.5 seconds.