How do you disable the sound calling makes?

You could change the sound associated with the call and use a short, "blank" sound file or a very soft sound. It's probably voice_ringing.wav. You might have to redo this after a Steam update as Steam requires administration rights, when installed in Application folder (by default) and might overwrite the file. If it's installed elsewhere, it's still able to overwrite the file.

You can replace the following default sounds.

Program Files\Steam\resource

voice_busy.wav

voice_dialling.wav

voice_ringing.wav

warning.wav

Program Files\Steam\Servers

game_ready.wav

Another post there :

I finally replaced the message.wav succesfully!

Every time I changed the wav, and I restarted Steam, the old message.wav returned, but now, I changed it again to a much more soft sound, and set it to "ONLY READ".

Now Steam can not change it back and I'm cool with my new sound!

Here are the steps:

• Grab a sound.
• Convert it to wav.
• Go to Steam/Friends.
• Replace message.wav with the new sound. Name it message.wav again.
• Set it to "Only read".
• ????????
• MASSIVE PROFIT.