Personally, when looking for Sounds I like to use freesound.org, I found it to work great for whatever I need including a nice suspenseful sound effect for that Puzzle game I'm working on. I always look for sounds marked with Creative Commons rather than Attribution because I'm not ready to add a Credits tab to my projects yet whatsoever.
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When I figure out how to make a decent looking Credits page, I will look more into using Attribution sounds-- but for now that's how I look for decent sound effects to use in my projects.
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