Hi, if you want any chance of some help on this, you really need to read the "How to use this forum - please read." message first. You clearly haven't and I bet that's why no-one has responded yet.
You need to edit your original post, enclose your sketch within code tags (see the # button) and explain your circuit much more clearly, including a schematic or at least a clear picture. Your brief description is confusing and seems to contradict itself (e.g. the number of LEDs). The schematic can be hand-drawn as long as it is clear (as a civil engineering student you should understand how important diagrams are).
You say the amplitude reading is always zero, which points to a problem with the part of the circuit that feeds the audio signal to the Arduino, and you have told us nothing about that yet.
Paul