Megila Reading on PA System

 Igros Moshe (OC II #108) Question Can the Megila be read over a pa system? Answer It is difficult to give a clear answer to this question. The problem is determining the precise nature of the sound that is heard through a pa system.  Because of this problem it is best not to use a pa system for the Megila reading.  In fact no one has asked me this question before and I don’t recall your claim that I told a young rabbi not to protest against its use.  However I disagree with your view that hearing it on a pa system does not fulfill the mitzva because it is like hearing from the reading of one who has no obligation to read.  According to the experts I talked with, the sound that is produced by a pa system is not the actual sound of the person speaking into the microphone but it is like an echo that is the direct result of the original sound. Therefore it cannot be simply described as if it were made by someone who is not obligated in the mitzva. However I am uncertain even after hearing the experts whether the sound produced should not be considered as if it were the sound of the person speaking into the microphone. and it is to be viewed as a new sound which is derived from the original.  That is because when listening directly to a person reading, you don’t hear what comes from his mouth but rather it produces a sound which is replicated a number of times as it goes through the intervening air. So is the pa system viewed simply as an electronic transmission which is comparable to the natural sound transmission or is it to be viewed as something totally new?.  Thus its nature is unclear. Because of this doubt it might be possible to say not to protest the use of a pa system and you can’t state definitely that this against the halacha or that it should be prohibited since it might lead to additional problems if utilized for shofar and Torah reading on Shabbos and Yom Tov. However this is not true because it is already prohibited to use a pa system on Shabbos and Yom Tov. Nevertheless even though you can’t protest because  of those reasons but since the justification for using it is unclear and this is a major new innovation which might encourage other innovations something which is a strong problem in America it is best avoided as you have suggested.