The Modest Orgasm

"Not everybody makes much noise about love. Oh, I know some people are huffers an' puffers, but others are silent lovers."

—Brick, Cat on a Hot Tin Roof

The female orgasm comes in many shapes and sizes, from loud and vigorous to soft and subtle. Well, it does in Real Life at any rate.

In television and movies however, the various censors don't like female orgasms. Or at the very least, not loud and boisterous ones (Herbal Essences commercials notwithstanding). As you might imagine, this is something of a Double Standard, since male orgasms don't suffer the same treatment (mostly, they don't get shown.)

So rather than show a woman in the throes of pleasure, the orgasm is either muted or replaced altogether with a symbolic substitute. This is the "acceptable" PG-13 way of showing a female orgasm- the only exception to this is when the orgasm is made ridiculously loud for effect.

Due to the widening of markets in recent years and the preponderance of R-rated movies and even television shows, this trope is getting to be much more out of vogue. See The Immodest Orgasm for this trope's successor and The Grunting Orgasm, the male version. On the other side of the coin, euphemistic symbolism for male arousal is covered by Something Else Also Rises.

No real life examples, please; we don't care, because it doesn't matter from a storytelling point of view.

Examples of The Modest Orgasm include:

Film

Several directors are interviewed about this trope in the documentary This Film Is Not Yet Rated. It goes into quite a bit of detail about the Double Standard and also how incredibly selective it is. One truly bizarre sequence has scenes from films approved by the MPAA contrasted with scenes banned by the same organization. The movie's big overriding question is what exactly the MPAA's rationale is- two naked lesbians under bedsheets are a moral disgrace, but the infamous masturbating into an apple pie scene in American Pie had no apparent problems. One reason is that the former came from an indy studio, while the latter from a major studio, but homosexual content in general seems to be subject to stricter censorship than heterosexual content. Whether this is because of inherent prejudice or, as noted above, the fact that most homosexual content tends to come from independent producers with little negotiating power (or, of course, both) is not fully revealed.
The sex scene in Titanic, which occurs off-screen, uses a symbolic fingertip-smearing of a car's windshield in lieu of an orgasm.
In Amelie, during the sequence when Amelie is imagining how many people are in the midst of orgasm ("fifteen!"), the last woman's O sound is somewhere between a gasp and a squeak. Amelie is far from modest. On the other hand, the rest of the montage (and the bathroom scene later) are a little less subdued.
Pleasantville. "Oh, my." Tree catches fire.
The Movie of Watchmen has a sex scene between the second Nite Owl and the second Silk Spectre where a flame thrower is used to imply orgasm. The same scene is found in the comic as well, but this trope is mostly for TV and movies.
The Fifth Element movie; Ruby Rhod has seduced a flight attendant and is having sex with her while the shuttle's taking off; her silent scream of pleasure is intercut with scenes of the rocket blasting and rocket engines firing, and then we just see her booted legs - sticking out beyond the cubicle curtain - slowly relaxing and slumping.
Forgetting Sarah Marshall has perhaps the most modest orgasm possible, where the protagonist is trying to forget Sarah Marshall by sleeping around with a multitude of gorgeous models, which is intended to show how models are closer to mannequins than they are to people..

Model: [Dead monotone] Oh. Oh. Oh. Oh. I just came. Oh. Oh. Oh.

In The Matrix Reloaded, the Merovingian illustrates his "Cause and Effect" speech by delivering a specially prepared (programmed?) dessert to a woman in the restaurant. She is somewhat surprised at the effect it has, but maintains her composure with aplomb. (See 3:34 et seq.)
Jackie in Red Road displays this, to the point of it creeping out her boyfriend.

"Did you finish?"
"Yeah."
"I can never tell."

Though this may just be her reaction to sex in general rather than orgasm in specific, Marie Antoinette (in Sofia Coppola's 2005 film) simply gives a pleasantly surprised "Oh."
Dana Delany in Exit to Eden
An extremely passionate hook-up between the hot chick and her not-boyfriend in Cabin Fever ends with a surprisingly mild gasp and hair toss by the woman, who then collapses on to her lover. The guy didn't make any noise at the grand finale, but that's probably because he was being smothered under a couple of 36D pillows. That's how I wanna go.
Shannon Tweed in Hot Dog: The Movie (although with Duran Duran's "Hungry Like the Wolf" blaring on the soundtrack any screaming would have been drowned out anyway, she clearly, er, comes and goes without saying a word).
Shanti Carson in Shortbus. Although in many ways her scene is as immodest as one can get seeing as a) it takes place during an orgy and b) her scene and all the other sex in the mainstream film is famously unsimulated, the actual orgasm itself is quite subtle. According to the behind-the-scenes featurette on the DVD the orgasm was real, making this one a borderline real world example, too.
In Enemy at the Gates, Vassili and Tania are having sex in the bunker and have to be very quiet so as not to wake their sleeping comrades. She manages to be quiet when she comes but he covers her mouth for good measure anyway.

Live Action TV

In Firefly, Inara (the Companion) is actually introduced mid-intercourse, with very muted sounds from both her and her client. The actual moment of orgasm is very brief; Inara softly gasps "Oh my God," and a moment later the camera goes softly out of focus and then back in (double entendre completely unintentional). This is very artsy, and actually quite a beautiful scene (irrespective of its content).
Battlestar Galactica was apparently asked to reduce an orgasm scene, only to respond that they had a Cylon orgasm (with flashing lights in her spine!) in the pilot. This was eventually retconned, since it had implications for the ease of Cylon detecting. Human spines can't light up. How can you miss a luminescent spine in an examination?
- How many people do you know of would be willing to have their sexual activities observed under the premise of checking their spine for orgasmic luminescence?
  - Quite a few!
    - I think he means that the mechanical/physiological properties of the Cylon spine that allow it to glow, should also distinguish it enough from a regular human spine that you could pick it up on a medical examination.
  - Of course, certain sexual positions would also make it possible to see someone's spine glowing during the act as well.
Played with across two seasons of Desperate Housewives. Andrew talks about "mm-mm!" being the only sound Bree makes during an orgasm, shortly before we hear her make the same sound over a slice of pie. The next season, we find out she never actually has had an orgasm, and is afraid she's sick after her first one.
Sofie in Carnivale in "Road to Damascus." While with Ben in a truck cab, Sofie starts gasping and squeaking, and then there is a bright bolt of lightning and a loud crack of thunder.
- It also hints at Sofie's true nature as Brother Justin's daughter, with the same avataric abilities as Ben, (who similarly used them to alter the weather in the first season) which the entire second season was leading up to. And then it was cancelled.
In the Buffy the Vampire Slayer Musical Episode, "Once More, With Feeling", Willow and Tara have metaphoric sex at the climax of Tara's song "Under Your Spell". Tara's orgasm is represented by her being levitated, which ties into the magic-as-lesbianism metaphor that has been playing throughout their relationship.
- Kind of a weird juxtaposition of modest and immodest: her orgasm is levitating, but she is also singing "You make me COM-plete!". I'm not musical, so I couldn't say the exact notes, but the first syllable is definitely a lot higher and louder than the second.
- When Willow and Kennedy have sex in the Season Seven episode "Touched", their sex scene is juxtaposed with Robin and Faith having sex, Xander and Anya having sex, and Buffy and Spike lying in bed holding each other, with music playing over the whole thing. Willow's orgasm is shown by her eyes going very wide.
In the Made for TV Movie The Marla Hanson Story, one of Marla's roommates asks the other roommate to turn down the TV set so she can listen on Marla while she's having sex with a guy.
A season four episode of Gossip Girl opens with Blair lying in bed, making smiling faces and a content sigh here or there. Then we find out Chuck was under the covers, getting a head start on their morning...

Video Games

In the first Mass Effect, during the encounter with the Consort, the camera cuts from the characters' faces to the Consort's hand as it reaches for the sky, then falls.
Whenever Beautiful Grunty is talking during the Game Over cutscene from Banjo-Kazooie.

Western Animation

An episode of Aeon Flux had a woman screaming during a sexual encounter, but MTV only allowed this on the condition that it sounded like a scream of pain rather than pleasure. As if that helps. What makes this whole fact more amusing is that the method of "intercourse" involved is direct stimulation (using tools like forceps) of the exposed spinal nerves inside a surgical opening the woman had in her back. The lesson learned: That it's okay to have decidedly-disturbing sex scenes, but it's not okay to make it appear that someone's actually enjoying it.
British porn in Family Guy.

Other

Sometimes seen on Beautiful Agony. Immodest orgasms are much more common on that site, though.
Truth in Television. Apparently it's possible for some people to reach orgasm in public and not have anyone notice. According to Cracked.com, "you probably sat next to one on a bus at some point".