To make the steps louder, you will need to use several possible ways at once.

The first way is to use special console commands. There are several of them and they look like this:

Snd_headphone_pan_exponent 2;
Snd_front_headphone_position 45.0;
Snd_rear_headphone_position 135;
Snd_mixahead 0.05.
This list of console commands is recommended for every player who wants to improve the sounds of steps.