The ruling on praying on a floor different from the imam's floor

Question:
In the King Saud University student housing, there is a mosque in one of the buildings, on one of the floors. During the prayer, it fills up with worshippers, which leads some people to pray on the second floor by following the microphone. What is the ruling on praying on the second floor while following the imam on the first floor?

Answer:
It is well known among the scholars that it is not valid, though some scholars hold that it is valid. The safest course for the believer is to pray alone with the group with him, so that each floor prays on its own. This is unless there is something between them that allows the people on the second floor to see and be seen; if the sound cuts out, they can see the imam or the worshippers, in which case there is no harm. However, as long as some of them cannot see others, and the only means is the loudspeaker, it is recommended not to follow, as stated by a number of scholars. Each floor should have its own people, and they should pray there if a place that can accommodate them all is not available. If a place that can accommodate them all becomes available, it is obligatory for them to gather in a mosque or a specific location, if there is no mosque, so that they can all pray together. If that is not possible, then each group should pray on its own in the place that can accommodate them.