Most of my work involves public speaking. Recently a situation has developed where my left ear blocks up when projecting my voice to an audience < this only happens when I am speaking to an audience < the problem can begin after an hour of public speaking; sometimes it can kick in a little later; occasionally it does not happen at all < when it starts, it keeps coming back during public speaking time < when I stop speaking loudly it goes away < it is not painful, just annoying as it muffles the sound of my voice < only very occasionally I have had this problem in the past but now it is more frequent. I am 63 years old < I have had my ears rinsed by a doctor removing wax blockages but it hasn't resolved the problem < I am trying to figure out what triggers it: swallowing, for example, I drink about half a litre of water (sometimes more) over a four hour public speaking session < has it something to do with the way I use my voice? Many thanks.