Editing and Mixing Sound: Frequency, Volume and Content

From a large action sequence to a subtle conversation, a huge amount of thinking and planning goes into the sound design to create an engaging, believable and pleasant listening experience. Not only does pacing need to be accounted for, as well as which sounds are needed, but considerations for the frequency and volume are paramount to getting a good mix.

Let's take a couple of examples, mentioned above; an action sequence and a subtle conversation. These are both quite distant in terms of content and frequency, and must be planned thoroughly as such. I'll break each down into relevant components so it's easier to account for.

The Action Sequence:

Set the scene: Let's take a place of action similar to one of the fight sequences in 'Inception'; it's raining, there are many cars driving around with 3 or 4 chasing the main characters in their car. Of course, these cars are crashing into other cars and objects, while the 'henchmen' all have guns of varying power, attempting to kill our protagonists'.

I must first stress something - this is only one of many ways to go about designing, composing and implementing the sound for a scene, regardless of it being an action sequence. It's really up to the director and the way he wants to take the action, or the Lead Sound Designer who may have a particular vision or style. A lot of other films might have had fast paced music over the top of this, but Richard King (the Sound Designer behind Inception) went with a more dynamic approach; bringing forth a much higher impact than if designed otherwise.

Break down into layers:

• Ambience - Throughout the scene, rain is falling fairly heavily. However, you'll notice the sound is particularly low in volume. The reason for this is to help enhance the dynamic range, which (as stated previously) in necessary for the impactive sounds. In fact, the ambience will likely be taken out at sections where the sound gets busy (crashing, gun fire, louder sounds in general). The same goes for the section where the train appears. Just before this occurs, you'll notice the dynamic range is heightened by leaving only the ambience in at a low volume before the train crashes into the initial cars.
• Dialogue - Although there isn't much in this section, the dialogue is seemingly set back in the mix, which is another device to increase the impact that crashing and gun fire has.
• Foley - This is a part of the sound that takes some picking and choosing. Much like a camera can focus on one part of an image, sound (when designed effectively) will do the same. If there is a man walking in the back of a shot out of focus, you generally wouldn't place footsteps on him. Similarly, if 5 or 6 people are shooting guns, but the camera is focus on a particular person, the sound would be mixed towards this person with their gun being loudest and possibly even leaving the sound out altogether for some of the other guns.
• SFX (explosions, crashes) - In this scene, explosions, crashes and gun fire certainly take precedence. My way of thinking about a mix is to concentrate on the loudest and most prominent sounds, and then add other sounds around them. This way, you get a sense of perspective and shouldn't make too many mistakes in the way of bringing down the dynamic range.

Frequency Content: There are quite a lot of thing going on here. One thing is getting the sounds in, synced and mixed in volume, but making sure they don't clash in the frequency range is hugely important.
Let's consider the ambience first of all. This sets the initial scene, much like a backdrop at a theatre will do. However, you wouldn't have any bright objects or 'loud' images on this, as it would take the attention away from actors and props on stage. So in terms of frequency, you need to leave quite a lot of room for other sounds to happen, such as dialogue, foley and SFX. Therefore, you'll want a low-to-mid range frequency band - this leaves room for low frequency explosions, mid-to-high dialogue and the high-frequency chinks of bullets landing on the tarmac. In short, you'll want the ambience to accommodate all the other sounds; surround them, fill in the gaps.
Dialogue and foley will have a similar frequency range, but different from other scenes or mediums. These would usually take up more of the lower end, taking advantage of the proximity effect in Dialogue or intimacy in foley. However, for this type of scene, any lower frequencies would be EQ'd out (or recorded as such) to leave space for explosions and gun fire.
I've said it enough already, so let's finally get to SFX. These will take up the largest range of frequencies, as the breadth of SFX is quite large in this instance. Explosions, for example, will take up the majority of the lower end, with car crashes similarly lower but with higher crunching sounds layered over. Car engines would usually take up the lower end, but with so many short bursts of lower frequencies, they've designed them to take up more of the mid range. Gun fire will depend on the size of the weapon: hand guns have shorter low-to-mid bursts, with automatic weapons taking up more of the low end.

Fluctuations: As with an overall film, a scene can have fluctuations of frequency content, as to 'fill out' any gaps. For example, I said earlier that cars take up the mid range more here, but for some shorter sections, the frequency tends to the lower-mid. They can get away with this because of so many cuts and perspective changes image wise.

The Subtle Conversation:

Set the scene: As a big fan of the show, I suppose it wouldn't go amiss to use a scene from The (American) Office as an example of subtle conversation - there's certainly a good amount of it through the entire shows catalog of episodes, ranging from whispered chats to shouting battles.

Break down into layers:

• Ambience - In this instance, ambience takes up quite a lot of room in the mix. In a way, the ambience in The Office is very much a character in itself. That is, it sets the scene and changes dramatically depending upon the circumstances. Most of the time, it's made up of fans and air conditioning, layered with SFX (detailed below). As there isn't much going on in the way of needing a huge dynamic range, the volume is brought up right behind the dialogue, and fills out the remaining frequency range (more on this later).
• SFX (Copier, Phones, Doors) - These SFX are placed strategically and help further set the scene and create a 3D space around what you see. In fact, this is a great example of sound continuity. When the camera is facing one way, there will always be something going on around and behind it. These SFX are placed almost as jigsaw puzzles to complete that picture. See someone walk off camera towards a door? The designer will carry on the footsteps and use an opening door sound to signal and bring closure to that movement. Back to the point on hand though - the levels tends to be reliant on how far the objects are from the camera, which gives a sense of depth to the room.
• Dialogue - For intimate conversations, Dialogue takes more priority than any other sound. Here, the volume tends to stay at a similar volume (regardless of speech type such as whispering or shouting). When the camera is taking a close-up, the proximity effect is utilised to give the sense of intimacy through sound.
• Foley - In some cases, the foley can take as much precedence as the dialogue in terms of volume and content. The Office, as you might imagine, involves a lot of phone, keyboard and paper handling. These sounds are therefore quite high in the mix and are used as focus tools. For example, some scenes don't have a lot of dialogue, and use the foley to tell a miniature story. This can anything from someone pretending to read a magazine while spying, or Kevin eating a cupcake.

Frequency Content: For The Office, there are some distinct differences in the frequency ranges of each component, but they fill the same gaps for the most part. Of course, the only change here is that there aren't any cars crashing or guns firing, so there's little need to take up that lower frequency range of 60Hz and lower (unless someone punches a wall...).
Ambience now takes up a much larger part of the frequency bandwidth, with more lows and low mids that would otherwise be used by explosions and gun fire. Dialogue varies widely now, with shouting from afar being similar to the action sequence (mid range), while close-up shots use the proximity effect, utilising the low-mids and often lower. Keyboards would otherwise have a very 'light' sounds, taking up the mid-to-high frequencies, but here the sound involves some lower-mids too. Clearly with a show like this, they can use more varied frequencies for sounds that would otherwise not use them.

Fluctuations: Changes in sound are as important as changes in the image for a 'Mockumentary' style show such as The Office. With so many swiftly changing shots, quick camera movements and single-shot takes, it's important that the sound stays consistent and varies accordingly for the scene. Particularly with the one-shot takes, where the camera is walked through the office, sound has to change enough to offer an audible picture of the environment it's moving through. A good exercise is to find one of these sequences and watch it without the image - you'll notice a lot happening which would otherwise seem normal with the image; a consideration necessary for the Sound Designer when mixing everything. In fact, you could do this yourself at your own office or workplace: even there, you'll find fluctuations in volume and frequency content.

Conclusions:
From looking at these two examples, we can quickly see some correlations in the needs of a mix for film, TV or even any form of sound scape: regardless of the style, filling out the volume, content and frequency range appropriately is vital. You could argue the same for a song without a bass guitar; instead, the guitar would need to be 'chunkier' and the kick drum would have a more open deep sound to compensate.

These are thoughts you need to consider when designing the sound for your own project - is the frequency range, volume and content fulfilling the mix? Ask yourself this through the entire process: you won't want to be destructive in editing or mixing and find the decision was made in error.

I hope you've enjoyed this post! Please leave a comment if you have any thoughts to add, or better still, let me know of any personal experiences you've had with this kind of thinking.

Next Time: UDK Game Audio! - I'm finally going to dive into my love of interactive sound. This first post in the series of many will briefly touch on best practices of audio before getting to the importing stage and basic implementation of sound in a 3D game world.

Alex.