Jenni's 72-year-old grandfather has difficulty understanding her when she speaks, but he seems to understand her father much better. why might this be?

People over 70 typically have difficulty with sounds over 6000 Hz. The capability to hear deteriorates with age, though the loss is utmost for high frequency sounds. At age 70, for instance, sensitivity to sounds at 1,000 Hz is preserved, while sensitivity to sounds at 8,000 Hz is evidently diminished. As many as 75 percent of people over 70 years of age have experienced some decline in their hearing distance.