I'm so sorry that you had to face a harassment --a form of discrimination on your job. 
What you need to do is to contact EEOC (Equal employment opportunity commission) and inform them exactly what had been happening at your job. You can write a letter and make a copy, sent one to your boss and keep a copy for yourself. Make sure you documentation everything, the date and how you had voiced your concerns to your boss on numerous occasions that you were unable to hear when he had made announcement over the speaker and how you were not given a fair chance to know what's being said. Your needs basically been ignored and how tired you are of being treated this way. I believe it's worth a try, don't let them get away with it. 
