Fatwa ID: 04061
Answered by: Alimah Sabrina Saidova
Can one close his/her eyes during Salah for concentration? And also, can one recite their Nafal prayers aloud when alone or in the presence of someone?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
It is makruh to close one’s eyes during salah, but if it’s done to remove the sight of something that may distract one from their salah, then it is permissible.  One who is performing their salah alone has an option of whether or not they want to pray aloud or silently in the loud prayers (Fajr, Maghrib, Isha), but must pray silently in the silent prayers (Zuhr and Asr). The minimum for praying aloud is to recite so that another person (such as in the same room) is able to hear the one performing salah (without a maximum) and the minimum for reciting silently is so that the one praying hears himself and perhaps, he who is very close to him. 
Nafal prayers during the night can be prayed silently or in a loud voice. Nafal prayers during the day have to be prayed silently.
Only Allah Ta’ala knows best
Answered by Alimah Sabrina Saidova
Checked and approved by Mufti Mohammed Tosir Miah
 RaddulMuhtaar 1/645, DarulFikr
 RaddulMuhtaar 1/533, DarulFikr