Is it permissible to say "Allahu Akbar" (Allahu Akbar) in the mosque outside of Eid al-Fitr and Eid al-Adha?

Takbir (uttering "Allahu Akbar") is a virtuous form of dhikr (remembrance of Allah) that is legislated at all times and places where it is befitting. However, it is not from the Sunnah (definition) to raise one's voice with it except in situations where that has been legislated, such as takbir when encountering an enemy or robbers, or during frightening situations. Other than that, takbir should be done silently.