Audio wave amplitude decreased after FIR filter
As per Peter K. recommendation, I will reformulate my comment as an answer, instead of starting by asking:

I think the fact that the cutoff frequency of your HPF is 17KHz (your tone frequency) can perfectly explain why your signal is being attenuated. 

I would recommend you to try to move down the cutoff frequency of the High Pass Filter in order to avoid attenuating your tone.

BR