Pre-emphasis shapes a signal before it is sent and post-emphasis shapes it after it is received. The idea is to compensate for distortions that the transmission channel may/will introduce.
Radars also sometimes use this to spread a pulse and thus transmit more power. Then on reception compress the pulse to improve range resolution.
Since noise is constant per unit bandwidth , noise is thus greater with higher center frequency
i.e. bass 50 ~500Hz is lower bandwidth than 500~15kHz so the treble is amplified on transmitter and reduced in receiver so response net is flat.
I recall there is 15dB of pre-emphasis but I forget the breakpoint frequency.
i think there is a different view of PRESHOOT.
this is its definition : " Preshoot is a new feature designed to improve the signal in the following bit time by boosting the voltage in the current bit time"