Forvo

Forvo.com is a website that allows access to, and playback of, pronunciation sound clips in many different languages in an attempt to facilitate the learning of languages. Forvo.com was first envisioned in 2007 by co-founder Israel Rondón, and came to fruition in 2008. Forvo.com is owned by Forvo Media SL, based in San Sebastián, Spain. Forvo's 'About'-page states Forvo to be the largest pronunciation guide website on the Internet. It has been listed in the 50 best websites of 2013 by "Time.
All sound clips on Forvo.com are created by its users, who also have the power to vote on each clip, positively or negatively, in an effort to ensure that the highest quality sound clips have priority in the site's listings. The pronunciations are also reviewed and edited by a volunteer team of editors.
Forvo has an API to share its pronunciation with other websites.
Recommendations for adding words.
Forvo just encourages adding simple words but there are some exceptions that can be clearly found in their recommendations and policy.