We may find voices attractive for what they indicate about the rest of the speaker’s body:

Researchers from University College London found that, at least among a sample of 32 participants, high-pitched female voices females were found to be attractive because they indicated the speaker had a small body. Deep male voices, on the other hand, were judged as more attractive because they conveyed that the speaker had a large frame—but were found to be most attractive when tempered by a touch of “breathiness,” suggesting the speaker had a low level of aggression despite his large size. …

Beyond explaining the popularity of Barry White, the researchers say these findings correspond to much of what we know about voice preferences in the rest of the animal kingdom. Birds and other mammals, it turns out, have long been known to advertise their physical characteristics via the sound qualities in their mating calls.