Why is the audio volume level at 0 every time I start my Mac?

Solution 1:

I found the answer on AskDifferent's sister site Superuser.com:

Snow Leopard resets sound volume whenever I start my computer

In Macintosh HD / Library / Preferences / Audio there are two audio setting files. Delete them. Set your sound to the desired setting. Restart.

This solved my issue.

Audio settings Mac