Of course you can make a looping sound.
You just need to tell flashpoint you want it looped, like this,
class CfgEnvSounds
{
sounds[]={ambience};
class Ambience
{
name="Ambience";
sound[]={"Ambience.ogg",db-20,0,1};
soundNight[]={"Ambience.ogg",db-40,0,1};
};
};
Where ambience is the name of your sound file. Pop this into you description and Robert's your Father's Brother.