Messages are mostly misfiring for married couple

DEAR ABBY: My husband and I have been amicably married for 16 years. We enjoy each other’s company and are home together a lot. However, over the last year or so, I have had an increasingly hard time hearing what he’s saying. He sits in his chair and mumbles to the point where I can’t tell if he’s talking to me or to himself. He also tries to talk to me from the next room with his back to me, or when I have the sink running. No matter how many times or different ways I ask him to speak up, he doesn’t do it. He says he doesn’t like “shouting” at me and that other people can hear him.