It’s not uncommon in the theater for silences to say as much as words. But gasps? Moans?

Welcome to the world of The Vibrator Play, in which those involuntary noises, produced by reserved Victorian ladies trained to keep a lid on anything more impromptu than a delicate sigh, do in fact speak volumes about things normally left unsaid. Sarah Ruhl’s often uproarious, occasionally melancholy comedy, which bears the somewhat more decorous formal title In the Next Room, pulls the bloomers off a surprising 19th-century medical strategy: a fad, among the physicians of the late 1800s, for applying Mr. Edison’s electrical innovations to the treatment of “hysterical disorders” among the ladies of the leisure class. But the real eye-opener for many audiences will be the historically accurate observation that the play’s ironically named Dr. Givings, in prescribing clinical electromechanical stimulation to the point of “paroxysm” as a means of restoring anxious patients to their former bloom, has hardly invented some revolutionary new treatment. Far from it: His vigorously waspish new instrument is merely an efficiency improvement on a manual technique as old as the Greeks.

It will perhaps have occurred to you by now that in tackling what the literature describes, dryly, as “the reduction of female sexual behavior outside the androcentric standard to disease paradigms requiring treatment,” In the Next Room might have gone wrong six times before Scene 2. It might have been squirm-inducingly vulgar or tiresomely broad or unappetizingly clinical or embarrassingly earnest. But Ruhl is a singularly gifted playmaker, a writer with an instinct for unexpected images and a knack for observations mordant and witty and true, and she approaches her subject matter with a skeptical eye, an open heart, and above all a precise ear. And in the handsomely designed, attractively upholstered production at Woolly Mammoth, she’s being artfully served by the sensitive director Aaron Posner and a cast whose pitch is well-nigh perfect.

The second act? It gets longish, yes, as it insists on fleshing out various subplots: one involving the surprise (not really) attraction of a patient to the midwife who assists in her therapy; another involving the doctor’s high-spirited wife and the wet nurse who’s taken over that most intimately maternal of duties; a third involving mother, nurse, and a flamboyant young painter who’s come to Dr. Givings’ consulting room suffering from symptoms much like the ladies’. (Let no one say that the good doctor isn’t an equal-opportunity therapist—or that Ruhl, who’s often described as a heady, esoteric sort of playwright, is above the occasional poke joke.)

But Cody Nickell proves comically flighty and surprisingly kind as Leo Irving, that impulsive artist; James Konicek and Eric Hissom (the latter, with Nickell, key to the success of Posner’s effervescent Arcadia at the Folger Theater last year) are the amusingly blinkered husbands, each oblivious in his own way to the needs and changes of the woman with whom he is theoretically one.

Kimberly Gilbert puts her impeccable timing and her sharply calibrated physical-comedy instincts to ideal use as Mrs. Daldry, the patient whose initial complaints yield rapidly to an ill-masked enthusiasm for repeat treatments. And Sarah Marshall, playing the diligent midwife Annie, gets an oceanic laugh with little more than a reach beneath a sheet and an expression that melts from the workaday to the faraway.

Behind the guffaws—and there are many, many guffaws—the play’s heart beats passionately. Mrs. Daldry’s sensual awakening comes with a corresponding emotional opening that can only wound. The wet nurse (a quietly lovely Jessica Frances Dukes) exposes her own longings, only to clamp down on them again. And at the center of the story, always, is Katie DeBuys’ radiant, impatient Mrs. Givings, a bird magnificently caged until she discovers, in one of Ruhl’s signature dreamy transfigurations, a way to unlock the door for herself, and to invite her hidebound husband to step through with her. In charting her escape, Ruhl maps out the generous promise of sexual revolution—and in delivering a sex comedy with a head on its shoulders and a heart on its sleeve, she offers our often sour, eternally puritanical society a tonic for one big part of what ails it.