Ambient_Generic

Adding Sounds is easy enough place an Ambient_Generic entity (point based entity)
Pick the sound you want, (you have the option of listening to them right in hammer) adjust the volume
and name it. Also check the flags for the options you want.


Then in CS:Source you have to add a Logic_Auto entity (point based entity)
and set the following outputs
Go to the output tab of the Logic_Auto, hit the Add button and select
MyOutput = OnMapSpawn
TargetEntity = Name of Entity (Sound Name)
TargetInput = PlaySound
Set the Delay for .50 (half second)

Then hit the Add button again and select
MyOutput = OnMapSpawn
TargetEntity = Name of Entity (Sound Name)
TargetInput = StopSound
No Delay setting

There is a Problem in CS:Source where the sound will not play after the first round and
this Logic_Auto entity fixes that. (1 draw back is sound doesn't play in the first round).
You could place a Trigger brush to trigger the sounds also as the players touch the
trigger brush the sound plays (Trigger_Multiple or Trigger_Once)