This is where the file 'sentences.txt' in alvesounds comes up.
A level just isn't a level without some sort of sound in it, whether it be the sounds of computers in a computer room or a CD audio track.
Setting up equipment for noiseless recording
How to convert sounds to proper HL format using Goldwave
Custom Sounds Tutorial
A perfect mixdown for your ingame sounds.
the low tech way...
To create atmospheric soundeffects, you need to keep several basic rules in mind.
I explain how to prepare sounds so they loop properly in game.
Want to get those NPCs talking? Read on!
How to loop those ambient_generic sounds.
Play an MP3 in your mod's startup screen.
Recording and preparing sounds for use in HL. Some aspects also apply to Source.