Film is an audio-visual medium, and yet many people focus almost exclusively on the visual side of things. When filmmakers fail to consider their sound, they often hurt their projects far more than they realize.
The fact of the matter is that most viewers won’t necessarily notice great sound work, but they will ALWAYS notice bad sound work. Even if it’s subconscious, nothing makes a project seem amateurish more quickly than shoddy sound .
So while sound design is probably not why you became interested in film, it still remains a vital component during all stages of filmmaking: pre-production, production, and post-production.
Post-Production Audio#
Post-production is where a lot of the magic happens with sound. While there are a number of programs made specifically for editing and mixing your sound, on early DIY projects, you’ll likely want to work directly in your video editor (cough** Sequence! cough). To keep things from getting too complicated too quickly, this post is only going to get as advanced as a video editor can get.
File Formats#
As with video formats, there are many different file formats for your project’s audio. Rather than give you an exhaustive list here, we’re just going to walk through the three formats you’re going to encounter most often.
- WAV - A waveform audio file is an uncompressed audio file that will retain all the information of the original recording every time it is exported. As such, the file sizes tend to be large.
- MP3 - Perhaps the most famous audio file, the MP3 is so often used because the files are so compressed that they are easy to download, upload, or send to others. However, such compression will lose a lot of information in the file that there is no way to get back (MP3 is a lossy compression format so every time you export a new MP3, you lose information). When working on your film, we recommend staying away from MP3 unless absolutely necessary.
- AAC - While also a lossy file format, AAC (Advanced Audio Coding) manages to hold on to a lot more information than something like an MP3. Often times, you’ll have to compress your file at the end of your work flow so AAC is a good place to turn to in order to compress your audio for somewhere like YouTube without losing too much quality.
Syncing Audio#
When the audio from a scene matches up perfectly with the visuals from a scene, the audio is said to be “in sync.” If, while filming, you plugged your mic into the camera or recorded audio with your camera’s internal microphone, then the audio will already be in sync with your footage when it is brought into your nonlinear editing software. However, if you recorded your sound to an audio-recorder, then you’re going to have to get your audio in sync.
Now, some softwares have the capability to auto-sync your audio files with your footage. However, if you don’t have the capability to do that, then you can always manually sync. Simply go to the beginning of your audio file and find the first large spike in your audio wave form. This spike will likely be the sound of the clapboard being clapped during the slate. If you line up this peak with the first frame where the top of the clapboard has come in contact with the bottom, your audio should be in sync for the rest of the scene.
However, sometimes in the process of editing, you’ll find that the sound has gotten slightly out of sync. Rather than going back to the source file, you can usually get dialogue back in sync by looking for a “hard sound” in someone’s speech pattern to sync to. If an actor is making a “P” or a “B” sound at the start of the word, it should be relatively easy to line the audio of that word up with the moment their lips open to get everything back in sync.
Sound Editing#
When embarking on your sound editing journey, our first tip is to keep everything as organized as possible. Right off the bat, create a few tracks for your production audio + dialogue, a few tracks for background audio + fill, a few tracks for sound effects, and a couple tracks for music.
Now, the reason we say you should create a few tracks for each of these sub-sections is that unlike video editing, where you’ll be hard-cutting from one clip right to the next, you always want to fade your audio in and out. If you simply put two audio clips next to each other in the timeline, you may create a “popping” sound at the point of transition. Instead, you should fade your A-clip out and put the B-clip below it to simultaneously fade in. If you’re looking for a harsh transition, you can make that fade last only a frame to get your desired effect. The audience will hear it as a harsh cut, but without the unwanted pop sound.
Finally, be cautious about having true silence in your project. While some of the most powerful scenes in cinema come from the audio going quiet, there is very rarely a moment when nothing is playing on the soundtrack. This is where your room tone comes in. By constantly having a quiet background noise in your audio track, the audience will notice the absence of other sounds if you take them away. But since the constant room tone ensures there will never be complete silence, they’ll never think that their speakers have broken.
Adding Sounds in Post#
Now there are certain sounds that won’t be recorded on set that need to be added after the fact. Sometimes, these things are planned (you weren’t using real guns on set and now need gunfire) and sometimes they aren’t (the actors were talking over each other and you don’t have a “clean” take of an actor’s lines).
You may be able to find some sound effects online; others you’ll have to make yourself. If you create a sound effect yourself in post-production, this is sometimes called “foley” recording.
Sometimes, you may even bring your actors back to re-record lines in a process called ADR (automated dialogue recording). ADR is usually done because of some sound quality issue but it can also be done to adjust performance or even to cover up for a late in the game re-write (simply drop the line in when the camera is on a different **character and no one will know the difference). Just make sure to direct your actor to mimic their motions from when they shot the scene. If the scene shows your actor straining to cary something heavy, but then the ADR comes through with the clarity of someone recording a podcast, we’ll recognize that it’s fake.
However, a word to the wise, ADR and sound effects almost never sound as good as if they were recorded on-set, so try to rely on them as little as possible.
Sound Mixing#
To use a cooking metaphor: If sound editing is picking out all of your ingredients, then sound mixing is choosing how much of each ingredient needs to go into your dish.
Just like when you were recording, you probably want to mix your sounds so they play mostly in the -20 dB to -10 dB space while avoiding 0 dB like the plague. However, if your audio peaks because of a mixing error, you can always re-mix it to be quieter. If the audio was peaking when it was recorded, you’re going to be stuck with the distortion in the audio file, and no amount of mixing will save you. You’ll need to either drop in a recording from another take or use ADR.
Another thing to consider when mixing is how many different channels you want to use:
If you export your mix in mono, then when playing back your sound, it is going to come out of all speakers equally.
If you mix it in stereo, you’ll have to choose which sounds play equally, which play more through the left speaker, and which play more through the right speaker. This can be incredibly useful as much of today’s video content is watched while wearing headphones which have a clear left/right speaker breakdown.
Finally, you may also have a 5.1 mix. This set-up is used in movie theaters and in some home surround sound systems where there is sound coming from five normal speakers (center, front left, front right, back left, and back right) and then one low-frequency speaker (for rumbling bass sounds). While a 5.1 mix is great for something that will be played in a movie theater, it is really hard to mix without a proper mixing room and is almost always unnecessary for something that will predominately be watched on the internet. For a DIY film, our recommendation is to stick to stereo (though you’ll be fine in mono if sound mixing isn’t your cup of tea).
Conclusion#
While there’s certainly more to film audio than what we’ve said here (we haven’t even touched on music yet), we hope this gives you some idea of the sound considerations you need to keep in mind from a project’s conception all the way to its completion. If you do so, you can avoid the nightmare scenario where bad sound sinks an otherwise great DIY film.
Hopefully, that sounds pretty good to you.
(insert foley effect: drum roll to cymbal crash over loud laughter)