The artificial boosting of higher modulating frequencies to reduce the effect of noise is called as pre-emphasis.
The artificial boosting of higher audio modulating frequencies in accordance with prearranged response curve is called pre-emphasis.
In FM, the noise has a greater effect on the higher modulating frequencies. This effect can be reduced by increasing the value of modulation index (mf).
This can be done by increasing the deviation and can be increased by increasing the amplitude of modulating signal at higher frequencies.