One significant complaint owners have with their older dogs is the inability to communicate with voice commands once their hearing starts to worsen.
Unfortunately there are no readily available hearing aids for dogs, so we have to plan that our older dogs may have some form of hearing loss as they age.
Often, hearing loss is progressive as they are getting older but there is usually a breaking point where they stop being able to hear normal speech volumes of their owners and this looks like a sudden change in hearing. It is also very rare for a total loss of hearing in older animals. Often older dogs can still hear louder or lower pitch sounds. With quiet or high pitch noises being difficult or impossible to hear.
The good news is that we can still communicate with older dogs relatively well with visual commands or cues. If you have the ability to train your older dog with both voice commands and hand signals at the same time you may have faster success, but it is still possible to train an old dog new hand signals, even if their hearing isn't what it used to be. Teaching hand signals will make communicating easier, it will make the world seem less confusing to them, and it will reinforce your bond through a shared language.
First step is to identify the commands you need to communicate and make a list of these commands (i.e. sit, stay, food, go outside / potty, walk, bed).
Then identify distinct hand signals for each of the categories or have a visual cue for each of the categories. For the “sit” command you might use a clenched fist making a downward pumping motion and for “stay” an extended arm with an open palm. But not all communication has to be hand signals. Dinner and walk can be as simple as showing them their food bowl or showing them their leash, respectively. You may even be able to train them to bump into a bell near the back door when they need to communicate that they have to go outside.
Lastly, is to start using the hand signals consistently with your pet. This is the most important aspect which is identifying a set of signals you wish to use and being consistent with this set of signals. Use the same signal consistently, and use it every time you communicate. Use the signal even if they already seem to understand what you are asking of them. Consistency will be key.