In UT2004 there is a client-side sound setting controlling, how the volume of sounds falls of when moving away from the sound source. This so-called Rolloff value can be changed in UT2004.ini and with a console command in a way that allows to clearly hear sounds from the opposite side of the map.
Lock Rolloff is a server actor that enforces a minimum rolloff value of 0.4 (the default INI value is 0.5) and additionally makes it impossible to change Rolloff while connected to the server.
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in my subforum, please.