We performed single line shaker injections at 82Hz, for 4 different amplitudes.
 The injection amplitude dependence of the excited noise is also checked.

For the narrow peaks at 142Hz, 164Hz, 208Hz, and 262Hz, I plotted these peak amplitudes as a function of the injected amplitude. 
Only the 164Hz (2nd harmonics) looks a quadratic function, and the others look liner.