His voice was as intimate as the rustle of sheets.

The simile makes “intimacy” tactile and domestic rather than grand or romantic: a voice compared to the soft, private sound of bed linens shifting. It suggests closeness that is bodily and immediate—heard at the threshold of sleep, in a space where social performance drops away. At the same time, “rustle of sheets” can carry a faint erotic charge, implying whispered conversation in bed or the aftermath of it. The line’s power lies in its understatement: the voice isn’t loud or commanding; it’s quiet, enveloping, and confidential, evoking a relationship defined by proximity and secrecy rather than public declaration.