Yes, you can edit a sound file to match your needs. For example, you might need to change the pitch, crop or loop one of our sounds to fit your project. You'll likely be mixing our sound files with others to build layered ambiences, or more complex sounds for your work. This is all fine. However you can not claim that the edited sound file is a new sound and sell it, add it to a library or redistribute it in any way. The original copyright is still retained by us or our contributors and the sound is still licensed to you for your use.