Answer:
(Fatwa: 934/934/M=1433)
It is better to say Amen silently as it is a dua and silence is best in dua as it is mentioned in the holy Quran:
ادْعُواْ رَبَّكُمْ تَضَرُّعاً وَخُفْيَةً
Also it is mentioned in hadith:
خير الدعاء الخفي.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
