Was there silence in heaven when our Lord and Saviour was crucified?
"Silence", what is the right meaning of this word if we applied it to Heaven?
It is very helpful first to know how the Church see the meaning of the word "silence" in order to understand, why the Heaven must observe "silence" during the hour of Jesus Crucfixion.
According to Catechism of the Catholic Church "silence means contemplation".
Entering into contemplative prayer is like entering into the Eucharistic liturgy:..
Contemplative prayer is the prayer of the child of God..
Contemplative prayer is the simplest expression of the mystery of prayer...
"Contemplative prayer is also the pre-eminently intense time of prayer..."
"Contemplation is a gaze of faith, fixed on Jesus. "I look at him and he looks at me"..
"Contemplative prayer is hearing the Word of God..."
"Contemplative prayer is a union with the prayer of Christ insofar as it makes us participate in his mystery..."
2717 Contemplative prayer is silence, the "symbol of the world to come"12 or "silent love."13 Words in this kind of prayer are not speeches; they are like kindling that feeds the fire of love. In this silence, unbearable to the "outer" man, the Father speaks to us his incarnate Word, who suffered, died, and rose; in this silence the Spirit of adoption enables us to share in the prayer of Jesus.
In actuality when we seek to ask if the Heaven were silence, we infer that the Heaven or the angelic beings were in "contemplative silence" witnessing the Redemptive Act of the Crucified Saviour.
The next very important question before we can be ascertain if the ***"silence or contemplation" is needed at the hour of Jesus Crucifixion are;
What is the meaning of the "Crucified Saviour" and what is happening at that very hour at Calvary?
The name of God that He revealed to Moses was "I AM WHO I AM" or in Hebrew word it is written like this "YHVH".
Moses at the Burning Bush
…Then Moses asked God, “Suppose I go to the Israelites and say to them, ‘The God of your fathers has sent me to you,’ and they ask me, ‘What is His name?’ What should I tell them?” God said to Moses, “I AM WHO I AM. This is what you are to say to the Israelites: ‘I AM has sent me to you.’”
The link below expound the meaning of the Hebrew word YHVH and link it to what Moses described in the Book of Exodus and the Crucified Christ is the realization of the actual vision shown by God to Moses in the burning bush.
YHVH, Behold, the hand, behold the nail
So, Jesus Crucified is the very meaning of the name of God and Moses described what he saw in the burning bush is a "Crucified Man or Angel", and Moses gazing or beholding the vision of the promised salvation to the People of Israel.
At the hour of crucifixion at Calvary, Jesus was offering His life in atonement for all the sins of mankind. Jesus was offering His life as a pleasing "sacrifice" to Eternal Father.
If there is a "sacrifice to be offered", then there must be a Priest to offer the sacrifice.
Pope Francis said the "The Mass means repeating Calvary."
How do angelic beings participate in the Holy Mass? The vision of Catalina Rivas a mystic is worth reading;
The Holy Mass
Explained to Catalina by Jesus and Mary
In this link article, we can see how the angelic being behave and function and it worth noting that your cited passages in Book of Revelation Chapter 8, is what happening the Holy Mass and what the angels are doing as described in this vision during the consecration or the hour of crucifixion.
At that moment, the Virgin Mary said: “This is the miracle of miracles. I have said to you before that the Lord is not constrained by time and space. At the moment of the Consecration, all the assembly is taken to the foot of Calvary, at the instant of the crucifixion of Jesus.”
Suddenly some characters, whom I had not seen before, began to stand up. It was as if from the side of each person present in the Cathedral, another person emerged, and soon the Cathedral became full of young, beautiful people. They were dressed in very white robes, and they started to move into the central aisle and, then, went towards the Altar.
Our Mother said: “Observe. They are the Guardian Angels of each one of the persons who are here. This is the moment in which your guardian angel carries your offerings and petitions before the Altar of the Lord.”
At that moment, I was completely astonished, because these beings had such beautiful faces, so radiant as one is unable to imagine. Their countenance was very beautiful with almost feminine faces; however, the structure of their body, their hands, their height were masculine. Their naked feet did not touch the floor, but rather they went as if gliding. That procession was very beautiful.
Some of them were carrying something like a golden bowl with something that shone a great deal with a golden-white light. The Virgin Mary said: “They are the Guardian Angels of the people who are offering this Holy Mass for many intentions, those who are conscious of what this celebration means. They have something to offer the Lord.”
The final moment of the Preface arrived, and when the assembly said, “Holy, Holy, Holy”, suddenly everything that was behind the celebrants disappeared. Behind the left side of the Archbishop, thousands of Angels appeared in a diagonal line, small angels, big angels, angels with immense wings, angels with small wings, angels without wings. As the previous ones, all were dressed with tunics like the white robes of the priests or altar boys. Everyone knelt with their hands united in prayer, and bowed their heads in reverence. Beautiful music was heard as if there were many choirs with different voices, all singing in unison together with the people: Holy, Holy, Holy...
Now let's compare this vision to the passages in the Book of Revelation chpater 8 that you cited and see the similarites of what the angels are doing in Heaven.
Revelation 8 New International Version (NIV)
The Seventh Seal and the Golden Censer
8 When he opened the seventh seal, there was silence in heaven for about half an hour.
2 And I saw the seven angels who stand before God, and seven trumpets were given to them.
3 Another angel, who had a golden censer, came and stood at the altar. He was given much incense to offer, with the prayers of all God’s people, on the golden altar in front of the throne. 4 The smoke of the incense, together with the prayers of God’s people, went up before God from the angel’s hand. 5 Then the angel took the censer, filled it with fire from the altar, and hurled it on the earth; and there came peals of thunder, rumblings, flashes of lightning and an earthquake.
Revelation 8 New International Version (NIV)
In closing, we can see from the vision of Catalina Rivas that during the Holy Sacramental Mass a memorial of Jesus Sacrifice, all the holy angels are in adoring and in reverence as st ated "Everyone knelt with their hands united in prayer, and bowed their heads in reverence".
If during the memorial sacrifice happening at the Holy Mass, the angels are in deep silence what more during the actual hour of Jesus Crucifixion at Calvary?
So the answer is, the Heavens during the actual hour of Jesus Crucifxion at Calvary are joined together with the Blessed Virgin Mary who were described by St. John "standing at the foot of the Cross" together with the other Mary's.
The mystery question is, if Jesus is the "sacrificial offering" at Calvary, then who is the Priest who offer Jesus sacrifice to the Eternal Father?
Mary Virgin Priest, pray for us, is the answer given by St. Pius X in 1906 and confirmed by Pope Pius XII in his encyclical.
"...she, the second Eve, who, free from all sin, original or personal, and always more intimately united with her Son, offered Him on Golgotha to the Eternal Father for all the children of Adam, sin-stained by his unhappy fall." Pope Pius XII. Mystici corporis Christi, §110, June 29, 1943, Libreria Editrice Vaticana