Finding audio for your project can be challenging. Below is a list of different resources that will help you find the right audio to use for your project. Be aware, that many of these websites have license requirements that you must abide by to ensure you are generating a good product.
Adobe Audition Content
Before visiting any websites, be sure to review the Adobe Audition Content. This is a heavy download, weighing in over 30 gigabytes. There is a mixture of sound effects, loops, scores and other sound resources. (edit: it appears they have pulled the Soundbooth Scores for the moment).
Public Domain & Creative Commons
The following websites provide audio content that is licensed within the Public Domain and Creative Commons realms. Be sure read the licenses carefully and follow them carefully. If the license requires attribution, then be sure to add the correct attribution to the final product.
YouTube Audio Library
Free music for your video projects, be aware, some require attribution.
Pixabay
You should attribute the music, but it’s not required.
CCMixter
You must attribute the music in your project.
Incompetech
You must attribute the music in your project.
Audionautix
Licensed under Creative Commons 3.0.
Freesound
There is a mix of public domain and content that must be attributed.
CC Trax
You can search for different license types.
Opsound
Licensed under Creative Commons 3.0.
Musopen
A mix of public domain and Creative Commons licenses.
Digital History
To be used for educational purposes only.
Nasa on Soundcloud
Be sure to read the guidelines for use before using.
Stock Music
In contrast to public domain and creative commons, sometimes it is easier to license the content from a reputable source. The links below are good resources if you’re willing to pay for the right resources.