Asalamu-Alaikum,
If someone is too far away to hear the Athan must he still attend the
prayer in congregation?
Jazak-Allah

Praise be to Allaah.

If we assume that the muezzin is giving the call to prayer from the
roof-top of the mosque (without the aid of amplifiers), that he has a good strong voice,
that the one who hears him has good hearing, that the wind is calm and that there are no
barriers or noise that will prevent the sound from reaching people, then the person who
does not hear this call because of being far away is not obliged to attend the
congregational prayer in the mosque. Imaam Ahmad estimated the distance at which the voice
of the muezzin would be inaudible in such circumstances as being more than a farsakh (one
farsakh is approximately five kilometers). And Allaah knows best.