All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Ordering people to say 'Allaahu Akbar' is included within ordering the mention Allaah. Allaah says (which means): {O you who have believed, remember Allaah with much remembrance.}[Quran 33:41]. Allaah further says (which means): {…and glorify Him with [great] glorification.}[Quran 17:111]. Ubay Ibn Ka'b narrated that when the first two-thirds of the night are over, the Prophet calls on people: "O people! Mention Allaah, mention Allaah." [At-Tirmithi] So raising the voice by ordering people to say 'Allaahu Akbar' in order to make them hear, is permissible and there is no harm in it, but if there is no benefit for doing so, then it is more appropriate to avoid it, as some righteous predecessors disliked raising the voice when mentioning Allaah and when supplicating.
Imaam Al-Bukhari entitled a chapter: "The chapter of what is disliked in raising the voice when saying 'Allaahu Akbar'", and he quoted the narration by Abu Moosaa "When we used to approach a valley, we used to raise our voice saying 'La illaaha illa Allaah', and 'Allaahu Akbar', so the Prophet told us: "Take it easy and lower your voices, indeed you are not calling upon a deaf or a distant One."
Ibn Hajar said: 'This is evidence that it is dislikeable to raise the voice when supplicating or mentioning Allaah, this is also the view of all the righteous predecessors and the view of those who followed them.'
Allaah knows best.