Below is an old tutorial I wrote in 2010, a place to start.
Please try and correct this if you find errors.
In the program directory is a file called sound_warnings.txt,
in this file you can set the text strings that you want to produce a sound:
alert1 = Maxine
alert2 = #Help
alert3 = [PM from
alert4 = #GM
alert5 = You stopped harvesting.
In the sound subdirectory you need to find the following files:
sound_config.xml
and
snds_alert.xml
If the latter does not exist, open one of the other snds_****.xml files to create it.
In the snds_altert file define each sound with:
<sound name = "alert4">
<variant>
<main_sound>sound/sheep.ogg</main_sound>
</variant>
<distance>35</distance>
<priority>3</priority>
<type>warnings</type>
</sound>
Notice that the type is <type>warnings</type> and I have
replaced the standard alert sounds with other (much louder) sounds,
including some cool sound effects I found on the web.
Make sure the alerts are not also defined in another snds_file,
like snds_client, if they are, delete the entry there.
In the sound_config header the following definitions should occur:
<!ENTITY snds_alert SYSTEM "snds_alert.xml">
<!ENTITY snds_client SYSTEM "snds_client.xml">
In the <sound_config> section:
<!-- Alert sounds -->
&snds_alert;
Make sure the files are saved with the original extension and not .txt
Restart
I can now change the loudness of these sounds with the 'text warning sound volume' under the audio tab of the options