Is it forbidden for the mu'adhdhin to conceal the sound of the iqama from worshippers in their homes after having made the adhan audible to them via loudspeakers, and what should be done to prevent this mistake?

It would have been better for the man who was calling the Iqamah (call to commence prayer) to use a loudspeaker so that people could hear it, as the Iqamah was heard outside the mosque during the time of the Prophet, peace and blessings be upon him. This is understood from his saying: "When you hear the Iqamah, walk to the prayer," and from the saying of Ibn Umar: "When we heard that the prayer had commenced, we would perform ablution, then go out to the prayer." You have done well by forgiving the man, suppressing your anger, and respecting the elder. We advise you to go to the mosque early and to treat the mosque community with wisdom and gentleness.