Saying Takbeer loudly or silently when praying alone
13-12-2017 | IslamWeb
Question:
Assalaamu alaykum. I wanted to ask; when I am praying by myself (for example: the non-obligatory prayers, the Sunnah prayers), do I need to say the transitional Takbeeraat (saying Allahu Akbar [Allah is Most Great]) out loud?
Answer:
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ʻalayhi wa sallam, is His slave and Messenger.
It is sufficient to move your lips with the Takbeer and all the other speech in the prayer. You are not obliged to raise your voice to hear yourself, according to a group of scholars. This is the view of the Maalikis and the chosen view of Shaykh Al-Islam Ibn Taymiyyah, and Sheikh Ibn ʻUthaymeen 
declared it as the preponderant opinion in this regard. They all held that it is sufficient to move the tongue and lips and pronounce the letters properly.
Mawaahib Al-Jaleel, a Maaliki book, reads, “The minimum form of reciting silently is to move one's tongue with the recitation, and the loudest form is when he hears himself.”
Al-Mardaawi wrote, “Shaykh Taqiyy Ad-Deen Ibn Taymiyyah favoured the view that it is sufficient to pronounce the letters, even if he cannot hear himself, and he mentioned it as a view in his school of Fiqh. I say: I am inclined to this view.”
Sheikh Ibn ʻUthaymeen held this view as preponderant and said:
“With regard to the words ‘he says’, if we say that ‘saying’ is done with the tongue, is it a condition that he hears himself saying it? There is a difference of opinion among the scholars concerning this. Some of them say that there must be a sound by which he can hear himself, even if those who are next to him cannot hear him; he has to be able to hear himself. If he speaks without hearing himself, then this does not count as ‘speaking’. But this view is weak. The correct view is that it is not essential that he be able to hear himself, because hearing is something extra to saying and speaking, and if something is extra to what is mentioned in the Sunnah, then the one who says that it is required has to produce evidence for it. Based on that, if a person is certain that he has pronounced the letters properly but he did not hear himself, either because his hearing is weak or because of noise going on around him or for some other reason, then the correct view is that all what he says counts, and he does not have to do more than what is indicated by the texts, which is speaking.” [Ash-Sharh Al-Mumti’]
Allah knows best.