Shaikh Bin Baz rahimahullah was asked:
Is it allowed for the one praying alone to recite loudly in the loud prayers?
“It is legislated for him to do that as it is legislated for the Imam. That is the Sunnah. However, he does not raise his voice such that it does not harm those around him from the congregants or those making the remembrance of Allah or those sleeping due to the Ahaadith reported in that”.
Shaikh Ibn ul-‘Uthaymeen rahimahullah answered a similar question saying:
“As for the one praying alone, if he prays a loud prayer, then he chooses between reciting loudly and silently. He considers what is more invigorating for him and closer to the concentration. So he precedes with it”.
[Majmoo’ al-Fatawa wa Rasaail (13/74)]
The Lajnah (Permanent Committee For Scholarly Research And Ifta’) were asked:
If a person prays a loud prayer alone, does he recite loudly or silently?
“All praise is due to Allah. The Sunnah is to recite loudly due to the absence of evidence which obligates departing from the reciting it loudly”
The Proof for these opinions is the following:
Hafidh Ibn Rajab rahimahullah said:
“what does not have a need to be recited loudly, if this harms others from those who are busy in obedience, like the one who is praying by himself and raises his voice with his recitation, such that he mixes up one who is reciting next to him, then this is prohibited. The Prophet sallahu alayhi wa salam once came out to his Companions and they were praying, reciting loudly. So he sallahu alayhi wa salam said:
كلكم يناجي ربه ، فلا يجهر بعضكم على بعض بالقرآن
All of you are conversing with your Lord, so do not raise your voice with the Quran, one over another.
[Reported by Abu Dawood, Ahmad, and Nasaai. Graded Saheeh by Al-Albani in Saheeh Sunan Abi Dawood no. 1332]
And Allah knows best
Faisal Ibn Abdul Qaadir Ibn Hassan