Change the language back to the original default language, let it update, and then switch it back to English. This forces the launcher to re-verify and download missing voice-over files.
The 2011 version of Modern Warfare 3 was distributed in multiple regional editions. While the version often defaults to your Steam client's language, Russian or German physical copies sometimes lack the English audio/text files on the disc. call of duty modern warfare 3 english language pack link
For advanced users who want to verify the authenticity of files, SteamDB provides the backend data. Change the language back to the original default
Check the box for or simply change the Text and Spoken Language to English. let it update
