Creative Commons (cc) licenses enable the owner of a work to allow another party to re-use, adapt, and re-create with their work. Different types of CC licenses allow for different levels of re-use. Regardless of the type of CC license you should always cite and/or attribute the work you use to the original creator. Some licenses stipulate that a work may only be used in non-commercial settings. You can look at the license to find out how the work may be used. This article from the MakeUseOf blog describes what creative commons is and how and why to use it. If you have other questions about copyright, please see the Copyright FAQ
The resources below point you toward media that in most cases is licensed through creative commons.
The list below provides sites from which you can find sources for or create your own audio for the project you are creating.
The list of resources below will allow you to find images that you may re-use with proper attribution.