Dought & clear, - Sifat al-Salaah (description of the prayer) ->Saying Ameen out loud in Qunoot al-nawaazil (Qunoot of calamities).

When a calamity befalls us, the Imam makes the dua of Qunoot. Do the
worshippers behind the imam have to say "Ameen" loudly, or it is
adequate to say it secretly? Is it permissible for the imam to rebuke
the worshippers for not saying Ameen loudly? I would like you to
provide us with evidence if it should be said loudly.
Praise be to Allaah.
The fuqaha' differed concerning how the Ameen is to be said by the one
who is praying behind an imam in Qunoot al-nawaazil.
The Hanafis are of the view that there is no Ameen in Qunoot
al-nawaazil, because the Qunoot should be recited silently unless the
imam recites Qunoot out loud.
The Shaafa'is and Hanbalis are of the view that the Ameen should be
said out loud in Qunoot al-nawaazil.
According to the Maalikis, Qunoot al-nawaazil is not prescribed in the
first place, and the Ameen belongs to the Qunoot; if the thing it
belongs to is cancelled then it is cancelled too.
See:al-Mawsoo'ah al-Fiqhiyyah(1/116).
It says inMughni al-Mughtaaj(1/362): Note: The one who is praying
behind the imam should speak out loud in five places: four places of
saying Ameen: he should say Ameen with the imam (i.e., after he
recites al-Faatihah); in his du'aa' when he recites the morning
Qunoot; in Qunoot of Witr in the second half of Ramadaan; and in
Qunoot an-Naazilah (Qunoot of calamity) in the five daily prayers; and
if the imam makes a mistake in his recitation and a person praying
behind him corrects him. End quote.
Shaykh Ibn 'Uthaymeen (may Allaah have mercy on him) said: If we say
that Qunoot may be offered in the five daily prayers, if the prayer is
one in which Qur'aan is recited out loud, then it is well known that
the Qunoot should be recited out loud, and if the prayer is one in
which Qur'aan is recited silently then Qunoot should also be recited
out loud, as it is proven in the Sunnah that the Prophet(peace and
blessings of Allaah be upon him) used to say Qunoot and the people
would say Ameen behind him, and they could not have said Ameen unless
he was saying Qunoot out lout. Based on this, it is Sunnah to recite
Qunoot out loud even in a prayer in which Qur'aan is recited silently.
End quote fromal-Sharh al-Mumti'(4/47).
Thus it is known that if the imam recites Qunoot out loud, it is
prescribed for the person praying behind him to say the Ameen out
loud, but he should not go to extremes in saying it out loud, in such
a way that is contrary to proper focus (khushoo') and tranquillity, as
some people do, raising their voices as if they are on a demonstration
and not at prayer.
It is not obligatory to say the Ameen out loud, rather it is
mustahabb, just as the Ameen itself is not obligatory.
And Allaah knows best.