People will definitely notice the loop point if they're trying to sleep.
My Android app (Chroma Doze, est. 2010) uses this algorithm to splice noise segments together:
When adding two streams together, the perceived amplitude stays constant
if x^2 + y^2 == 1 for amplitudes x, y.
A useful identity is: sin(x)^2 + cos(x)^2 == 1.
Thus, we can perform a constant-amplitude crossfade using:
result = fade_out * cos(x) + fade_in * sin(x)
for x in [0, pi/2]
But we also need to prevent clipping. The maximum of sin(x) + cos(x)
occurs at the midpoint, with a result of sqrt(2), or ~1.414.
Thus, for a 16-bit output stream in the range +/-32767, we need to keep the
individual streams below 32767 / sqrt(2), or ~23170.
