You might find these useful.
- http://freegameassets.blogspot.co.za/ = With Credit Given ( Creative Commons License) - free to use Example: Krasi Wasilev ( http://freegameassets.blogspot.com)
- https://freesound.org/ = Freesound is a collaborative database of Creative Commons Licensed sounds.
- http://soundimage.org/ = This site contains original music, sound effects and images created by Eric Matyas , which you are welcome to use in your projects (commercial and non-commercial) with proper attribution to the creator.
Hope this helps!