Secrets to Trailer Sound Design
Movie trailers have a unique style of sound design where virtually everything and anything that happens on screen is accompanied by a sound effect. The only other place I've ever seen this is in reality TV shows which frequently use every editing trick in the book to heighten the impact of every look, reaction, cut and camera movement (just watch a few minutes of Hell's Kitchen and you'll see what I mean)
Supplementary sound design is often necessary for movie trailers because the film's sound mix is typically done at the very end of post-production. This means it's up to the trailer editor and/or sound designer to build it out. This is often why sound effects in movie trailers are completely different from the finished films. This goes especially for sounds of gunshots, swords, fight whooshes, which can sound more cartoony when pulled from old sound effects libraries.
If you've ever seen the editing timeline of a Hollywood movie trailer editor you're likely to find well over a dozen audio tracks full to the brim with sound effects. But the skill doesn't come from the quantity of sound in the sequence, it's from ensuring each sound serves a purpose and works well in concert. As of the writing of this post I feel a lot of trailer sound design isn't as aggressive as it used to be as it was in the early 2000s, but it still has its place.
Trailers (and sound design) don't get much more early 2000s than this (you'd probably do the same thing when you get digital editing after years of editing on film)
The main purposes of trailer sound effects are:
Atmosphere & Tone
Anticipation & Suspense
Transitions
Impact
Sweetening
Atmosphere & Tone is about using subtle (or not so subtle) sounds to create a mood either in lieu of music or in conjunction with it. These sounds are there to create a mood, set the scene, and tell the story through sound. Sound effects which achieve this are things like drones and atmospheres. Sounds like hits, whooshes, rises and booms can also contribute to the tone because a single hit can make a trailer sound like a comedy, blockbuster action film, horror film, sci-fi film or drama. Sound design which creates a real sense of atmosphere and tone can really immerse you into the world of the film.
Watch the trailer for any horror film or thriller and you're likely to get a crash course in trailer sound design.
Suspense and Anticipation sounds are about keeping the audience constantly on the hook so they're dying to see the next moment. With how fast cut trailers can be, you might be surprised how much work goes into constantly holding the audience in suspense to see the next few seconds.
One key sound effect trailer editors use to build suspense and anticipation is the "rise" or "riser." Feature films do this too where audio from one scene will start before the end of the previous one. For example, there's a scene in Silence of the Lambs which has the sound of a helicopter powering up underneath it which has the effect of making it feel tense; it turns out the helicopter appears in the following scene so it has the double effect of adding suspense and transitioning to the next scene.
Trailers use short rises to build anticipation and enhance the impact, while longer rises almost double as music to create a huge climax at the end of the trailer. Rises are like if there was a sound to the wind up of just about everything had a sound whether it's a punch, gunshot, explosion, etc. Any time you want people to be on the edge of their seat anticipating a big moment is when you might want to add a rise. They're also used to bridge scenes or acts of a trailer.
There's a long "rise" in the end montage of this trailer for District 9 (which ends when the mech catches the RPG) I'm pretty sure this same rise is used in many many other trailers.
Sound effects used as transitions are probably the one trailer sound which have the most commonalities with feature films and TV shows. Think of shows like 30 Rock and Scrubs which use whip pans to show cut away scenes. These sounds are used to move the viewer into a scene, transition from one to the next, or transition out of a scene. These are frequently done with whooshes which accompany dips to black, dips to white, cross dissolves, lens flares, etc.
Probably the number one thing trailer sound design does is to add IMPACT. Whether it's a title card slam, a traffic light turning from red to green, an accelerator being stepped on, a button being pressed, fists being cocked, or just about anything on screen which has a sudden, definitive motion. This also goes for edits, transitions and more. Pretty much everything in a trailer can be enhanced with some hits, booms, and impacts. A common trailer trope is an opening shot which starts with a low boom to get you in the mood.
A sound effect was notoriously added to Henry Cavil "reloading" his fists in this fight scene from the Mission Impossible Fallout Trailer.
Last thing pretty much all trailers do is audio sweetening, which is enhancing existing sound design. This is especially important if the official sound design either is in its initial stages or non-existent. Oftentimes audio is sweetened because the sound design of a scene is much subtler and would feel weak and empty in the heightened reality of a movie trailer. This means punches might sound more aggressive, car crashes more violent, guns more clicky and impacts more boomy. There's pretty much nothing in a trailer which can't be made less subtle.
Though keep in mind, this post is mostly talking about sound design for movie trailers. Game trailers tend to use much less sound design than movies. When I make game trailers I use less sound design because I know the sound of a game can be deeply tied to how a game feels to play, so I don't want to affect that perception from a potential player. The times I use more sound design are in cinematic story trailers, otherwise I typically restrict it to things like title cards and transitions.
I wanted this whale scene from the Psychonauts 2 Story trailer to have lots of impact, so I augmented the sound of the landing!
My recommendations for royalty free trailer sound effects libraries are all on this page. There are some very good libraries for as little as $50 USD. If you're new to adding sound design to trailers, I suggest starting by sound designing title card slams and motion graphics. They're one thing for which you pretty much always want to build anticipation and create a big impact. But if you're anything like me, you'll likely get your first sound effects libraries and want to design every frame of your trailers and over time get more judicious with experience.
If your trailer ends up with quite a lot of sound design I cannot emphasize how valuable it is to get a professional sound mixer to do your trailer's final mix. They somehow magically take a chaotic sound mix which sounds like multiple bands competing for attention, and make it into a harmonious orchestra where every instrument is an individual and yet contributing to the whole.
