Answer:
For a tube closed at one end the length of the tube is 1/4 λ,
Note: a closed tube at one end has node-antinode-node-antinode-etc
The fundamental is node-antinode for λ/4
In this case λ = 4 L
f = V / λ = V / (4 L)
L = V ( 4 f) = 340 m/s / (4 * 128 / s) = .664 m for the fundamental length