If you’re having trouble communicating clearly with an older person in your life, it might be that your regular speaking voice is in a range they can’t hear clearly.
There is a wide variety of hearing loss types that can affect our perception of sound frequencies across the board from extremely high frequency to low frequency. Age-related hearing degeneration—presbycusis—is pretty consistent, however. It affects one out of two people over the age of 75 and tends to cause a slow and marked reduction of the perception of high-frequency sound over time.
As a result, you may have noticed that your elderly parents, relatives, or neighbors tend to hear your deeper-voiced spouse better than they hear you. While your spouse might be an excellent communicator, the real secret is likely that more of the words they say fall within the frequency range the recipient can hear better.
So while you don’t need to do your best Isaac Hayes impression when talking to great-grandma, consciously lowering your voice a little will go a long way towards helping her, and the other older folks you chat with, hear you more clearly.