Sample Focus - The easiest way to find the perfect audio sample
Epidemic Sound - Website with licensed music to use in youtube videos
UseMySound - Free music for videos, ads, games & podcasts. Every week.
Zapsplat - Zapsplat Royalty free music is a website that covers an extensive list of royalty-free music, making you download over 85000 sounds effects in a very format like Mp3, FLAC, M4A, WAV, ACC, and many others.
FindSounds - Audio web search engine
SoundsCrate - SoundsCrate is one of the reliable websites that is designed to provide thousands of sound effects and royalty-free music, making you edit or create your own album.