Acoustic License

In real life, even in the best of circumstances we often have to repeat ourselves to be understood by the people we're talking to.

In fiction, when conversations are taking place, they will sometimes benefit from a strange, localized phenomenon of crystal clear acoustics. It doesn't matter if they consist of several paragraphs of Sesquipedalian Loquaciousness, the words will be heard without any trouble by both target and audience, even in the midst of a crowded nightclub dance floor being buzzed by a 747. A particularly handy feature for the The Quiet One, but also for action heroes making sure the villain hears their cool Pre-Mortem One-Liner despite them both dangling from a speeding helicopter.

Sometimes you might have to go so far as to TALK! LOUDLY!, but don't worry—unless it's a Plot Point that you shouldn't hear each other, then damn the acoustics, full speed ahead!

Contrast Fake Static, Plot-Based Voice Cancellation and Sound Effect Bleep for when the writers are inserting rather than ignoring audio obstacles.

Examples of Acoustic License include:

Anime and Manga

Both played straight and averted in Porco Rosso. Sometimes, people communicate plane-to-plane via morse code, as they did in real life. Other times, they simply shout, which in real life would have been impossible.

Comics

Comics are particularly susceptible to this trope, due to being a silent medium where it's less noticeable. It doesn't matter if guns are firing, entire city blocks are collapsing, or Galactus is eating the planet—it's a safe bet the villain will hear every syllable of the hero's snappy rejoinders.

Film

Airplane! has a scene where a couple continue to have a conversation as one is standing in the doorway of a plane in the midst of takeoff and the other is running along on the ground beside it.
Freejack has a scene where the hero is overheard talking by a camera crew from across the floor of a nightclub pounding with music.
Full Metal Jacket The scene in the helicopter where the gunner is getting interviewed while firing his gun. I know aircraft have headsets and microphones, but i can't really think of many examples where they USE them as intended, instead they act as though they're protective in nature (IE gun range earmuffs) rather than communication devices - instead electing to raise their voice or shout over the DIN.
Halloween Resurrection: Sara is in a college classroom in the beginning. When the professor asks a question, and she answers, her voice is barely higher than a whisper, yet the professor hears her clearly and responds.
The first Mission: Impossible movie features a climax where hero and villain are indeed hanging off a speeding helicopter. Following just behind a TGV Bullet Train travelling hundreds of kilometers per hour. In a tunnel. Given this it's probably just as well Ethan Hunt uses visual aids while shouting "Red Light! Green Light!", so that Phelps can properly recognize things are about to get a little 'splody.
Revenge of the Red Baron has a doozy of an example of this trope. Two WWI pilots in open cockpit planes, dogfighting each other, are able to trade threats and insults through the communicative power of shouting their lines.
Snake Eyes features Nicolas Cage's character Rick Santoro somehow not only hearing his cellphone ring while sitting in the front row of a crowded sports arena during a boxing match, but having a conversation on it with no problem.
At the end of the film version of 300, the narrator is talking to an army of over a thousand men. Somehow, the guys way in the back who are probably half a mile away, hear him perfectly fine.

Live-Action TV

House MD - The episode with the rocker with epilepsy triggered by chaotic music. House brings in a marshal stack and plays REALLY LOUD MUSIC... and then asks "so what were your inspirations for this" over the cacophony.
How I Met Your Mother - Averted in the fifth episode of the first season. The gang goes out to a nightclub, and while on the dance floor no one can hear each other, except when there's momentary lulls in the music.

Video Games

In the iOS game Highborn, the characters are often able to talk from across the map. This even gets lampshaded once:

Trillian: Wait, how are we even talking?
Enzo: It's a plot device; roll with it.