What should the congregation do if it can no longer hear the imam?

One waits a reasonable time and then continues the prayer alone. As soon as the imam can be heard again, one follows him from that point on, and the prayer is complete before God.

In congregational prayer one follows the imam step by step. If the loudspeaker suddenly fails, the worshippers lose contact. No one knows how long the fault will last. Even so, there is no need to feel unsure.

First one waits a reasonable time, until one can assume that the imam has finished that part of the prayer. Then one continues alone. What counts as reasonable depends on the moment. In prostration it can be hard to judge, because the imam sometimes stays there longer on purpose. Here it helps to know his usual habits. In the sitting between two prostrations, on the other hand, one quickly notices that contact has been lost. There one does not wait long.

As soon as the sound returns and one can tell where the imam is, one joins him again and follows him from there to the end. There is nothing to make up and no need to start over.

Such a prayer has no defect before God. The hadith above shows that the imam is there to be followed. Whoever has done that as well as they could has fulfilled their duty. The verses above remind us that God only asks what a person is able to do. A technical fault is not a failing of the worshipper.