Talbiya is to be recited aloud Sahih al-Bukhari 1548
Translation
Narrated Anas
The Prophet (ﷺ) offered four rak`at of the Zuhr prayer in Medina and two rak`at of the `Asr prayer in Dhul-Hulaifa and I heard them (the companions of the Prophet) reciting Talbiya together loudly to the extent of shouting.