What does "faces like the side of a mountain and wonderful voices like syrup being poured" mean in the passage (Paragraph 16) ?

In the Moustache Common lit

In this paragraph the speaker describes his grandmother's look, who is living in a nursing home. He compares her with Ethel Barrymore and says they both have "faces like the side of a mountain and wonderful voices like syrup being poured". He means they both have rough-textured skins, like most elder people, and that they have soft silky voices.