What is the reason why the microphone in the hotel conference hall sounds harsh and long from time to time?

That very harsh long sound you said; Commonly known as: howling; Sound system professional language call feedback;

It stands to reason that the hotel's audio configuration should not be bad; It may be a debugging problem; I wonder if there is an equalizer in the equipment; If there is, this problem will be solved very well; Especially the professional 3 1 segment equalizer is very powerful; The sound field can be adjusted; Suppress acoustic feedback; Make special sound effects, etc.

My other answers; There is an article specifically called the debugging of equalizer; Mainly used for acoustic feedback debugging; Please refer to; Should be helpful to you;

I don't know which city you are in; If in Chengdu; I'll try to come directly and adjust it for you; My QQ 1 184775 Baidu space has my other information.