There’s no mistaking the elfin figure in the size 4, blue suede mocs who answers the door to apartment 10-O. This despite the fact that her hair, only recently lifted from the pillow, is uncharacteristically swept up like a kewpie doll’s caught in a tornado. Or that, at 4-foot-7-inches, a visitor of average height might be forgiven for looking right over her to the panoramic view of the Hudson River that fills the living-room window.

But there will never be any confusing — and most definitely, no ignoring — that voice.

“Good!” Ruth Westheimer declares by way of a greeting in the singular guttural trill once described as equal parts Grandma and Freud. “You don’t have a photographer, so I don’t comb my hair!”

As the celebrated sex therapist turned 84 on Monday, the voice has aged but certainly not mellowed, so that it now sounds even more the way you imagine the father of psychoanalysis would if he were alive, female and insisting you try a piece of chocolate rugelach in upper Manhattan’s Washington Heights.

When Westheimer — who fled Nazi Germany as a child — reached the United States in 1956, people told her she had to escape that accent. But with a job that paid $1 an hour and a baby daughter to care for, she had neither the money nor the time for speech lessons. Now, Westheimer’s delight of the moment (one she’ll point out repeatedly today to those she meets) is that an actress who will soon play her on stage is paying a dialect coach so that she can sound just like Dr. Ruth.

“It’s nice to be Dr. Ruth,” she says. “Put that down.”

It’s been nearly 32 years since Westheimer broke into late-night New York radio with, Sexually Speaking, launching a career as confider-in-chief to Americans who, it seemed, had been yearning to share their sexual doubts and fears. The voice that Westheimer found on radio, and in the books and television shows that followed, pushed the boundaries of popular culture, declaring it not just safe, but healthy, for people to speak explicitly about their sex lives.

The timing was opportune, coming just as fears began to explode about a new scourge called AIDs. But so much has changed since then; the country entered the age of Viagra and Internet porn, sexting and gay marriage. Can an octogenarian grandmother who has never learned to use a computer, adapt to the changing times?

A generation after the country embraced the Ruthian ethic of sexual honesty and moved on, what’s left for Dr. Ruth to talk about?

Appearances count

“Can you hear me in the back?”

It’s just after 1 p.m. and Dr. Ruth has again claimed a spot in front of a microphone. Years ago, when she taped her weekly radio show on Tuesday afternoons, employees at NBC studios broke away from their jobs to listen in. Today, though, it’s the mic, atop a small stage in a Manhattan town house that is home to the National Council of Jewish Women, that isn’t working.

“We can’t even hear you in the front,” a woman calls from the second row.

Like today’s speaker, she and most others in the audience for this “lifelong learning” forum are female, Jewish and old enough to be well acquainted not just with grandmothering, but also widowhood. A couple arrive in wheelchairs and a few more lean in on walkers. Eventually the microphone cooperates, and Westheimer sets out ground rules.