I'm not deaf, I don't wear a hearing aid, and I just wish those actors would speak up and project! 
  Yes, I've often heard words saying as much and sometimes I think so myself. But I'm getting older, as we all are, and in everyday conversation we have words directed at us and can ask people to repeat themselves if necessary. Not in the theatre.
As we age, our ability to hear and differentiate certain frequencies deteriorates, perhaps without us noticing.... until we are in the theatre. There we may receive Volume but not Clarity. Then we blame the actors or the director. We may even think we are hearing effectively, but some words are lost, concentration becomes more difficult, our involvement is reduced, then we are disappointed. 
  All this was brought into focus by my King Lear experience at the Olivier. I should have heeded Fredo's advice to try out a National Theatre hearing device, but I decided to trust my perfectly adequate ears. In the first half I realised I was missing words, I was following the plot but without being involved. Many in the audience were hearing, were responding, were engrossed, were impressed, when I was not. 
  At the interval I collected a (free) hearing device from the Olivier Information desk...what a difference! Instead of struggling to hear from afar, all the words (well, most) sounded as if I was standing next to the actors. The dialogue was not louder but it was clearer, much clearer. I was able to relax into the play without straining to understand. Part Two of King Lear was a much better experience for me. 
  I know the vast auditorium of the Olivier, and sometimes the Lyttelton and other theatres, can cause audibility problems in certain seats, not always the fault of our ears. But often it is Us and not Them. Let's not seek to apportion blame. Hearing devices for anyone finding it hard to hear can be borrowed free of charge and they DO make a difference. There are types for people wearing aids and for others like myself who normally have no hearing problems (well, none I recognise!). These devices are now available in most theatres so ask and give them a try. They may not suit everyone, but you have nothing to lose and a lot to gain. 
  You can read about the facilities offered at the National Theatre HERE