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Horizon Zero Dawn Interview with Guerilla Games’ Audio Team

Sam Hughes catches up with the audio team at Guerilla Games about their work on the fantastic title, Horizon Zero Dawn. We had the pleasure of speaking with:

  • Bastian Seelbach, Audio Lead
  • Anton Woldhek, Principal Sound Designer
  • Lucas van Tol, Senior Sound Designer and Music Supervisor
  • Pinar Temiz, Sound Designer
Left to Right: Anton, Bastian, Pinar, Lucas

If you haven’t had the fortune of playing Horizon Zero Dawn yet then check out this awesome trailer:


Can you tell us a little about how you approached Aloy’s sound design as a child, and through to adulthood and how it changes as she grows?

Lucas: By far the most work went into Adult Aloy, because you only play a small chunk of the game as Child Aloy. So Adult Aloy has a huge set of different materials for footsteps, and a whole bunch of different costume sets that play on top of them. It was a lot of work that required the creation of countless assets, and we simply didn’t have the resources to do the same for Child Aloy.

Luckily, Child Aloy walks around on bare feet in the game, and doesn’t have access to the various armors and special actions that Adult Aloy has. We had to create a completely new set of footsteps anyway, because the sound of Child Aloy’s bare feet is very different from Adult Aloy walking around on soft soles. Since we required a new set, we took the opportunity to make them a bit lighter as well. Child Aloy’s walking and running rhythm gave her a different-sounding pace, due to the way the child actress was mocapped.

You may also notice that Adult Aloy sounds different throughout the game. As she grows in skill, she gains access to better weapons and armor. We had several sets of armor – each of which required different sets of footsteps, climbing foley, and so on – with different degrees of ‘heaviness’ or ‘stealthiness’. The type of costume Adult Aloy wears actually affects the sound she makes as she walks around.


How does the sound design vary between the Outcast land/wilderness, the Nora, bandits and various different tribes Aloy encounters on her journey?

Lucas: Anton put in place a system called Guerilla Dynamic Audio (GuDA), which keeps constant track of various game states, including location. This means we know which region the player is in, like Nora, Outlands, Carja, Bunkers, Ruins, etc., and also what kind of habitat or environment we’re dealing with, like forest land, grasslands, mountains and so on.

Based on this information, the system decides on a lot of things to help differentiate the locations. What kind of music do we play in the background? What kind of reverb do we apply to sound effects and dialog? What kind of wildlife is available in that particular habitat at that particular time of day?

It also affects the weather sounds – rain and wind, which is particularly apparent close to the Bandit Camps, which are usually located in areas where it is more likely to rain. Together with the music that was written specifically for the Bandit Camps, this creates a completely different mood even without any enemies around.

A lot of the machines seem to have real life elements to their cries and movements, for example The Strider sounds a lot like a horse, but how did you decide what real life elements to include and what to add or mix with these elements to make them more like machines?

Pinar: As far as I’m concerned, there wasn’t a magic formula for this. Of course, we did set some guidelines for ourselves, based on the visual style and intended realism of the game in general.

You can think of those guidelines as limitations that were necessary for the creative process. Some guidelines were stylistic choices, such as “Do not use too many metal sounds in their raw state; process and mulch them into more synthetic sounding textures with various FX chains”. Also: “Avoid exclusively using synthetic sounds – sounds not grounded in ‘physical world’, so to speak – and if you do, process or layer them with more earthly, organic sounds so they’re re-grounded in the world’s physical reality.”

These guidelines were mostly adhered to for movement sounds. The process for the vocalizations was more experimental, but still not far off from this guideline exercise. We found that a mix of actual animal sounds, or any organic material textures that carried an emotive quality, could be used as a layer. Again, processing raw materials to give them a slightly synthetic feel was a trick that we played a lot with. Sometimes it’s the FX chain one comes up with; sometimes it’s the content combination, or how you implement it, which seals the deal.

From a conceptual standpoint, the main challenge with the vocalizations was finding a balance between ‘machine’ and ‘animal’ for any given robot. Some machine designs clearly referenced real-life animals, while others didn’t – yet they still acted alive and sentient. There were times where the balance would tip over to one side, and then to the other. I don’t think there was a single correct answer for this process; at the end of the day, it was partly a gut feeling, a sense that we got ‘there’ or at least close enough for it to work.


How do the soundscapes change according to the day/night cycles in the game?

Anton: Handling the general sound environment of an open world game was one of the big, obvious questions staring at us when the team decided we were going to make Horizon Zero Dawn. But we’d already anticipated this decision during the early days of Killzone Shadow Fall’s production. A big reason to create our nodegraph system was because we knew that, although we could create a great shooter with our previous tools, it wasn’t possible to go beyond that. We wanted to create comprehensive systems – systems able to react to day and night, to location, but also to any other input from the game, such as the number of machines present and their ‘emotional’ state. And we wanted those systems to be very flexible, to act more like content than like hard-coded mechanisms.

In order to support this idea, we created the ‘Guerrilla Dynamic Audio’ system – GuDA for short. I like to call it the mother of all sounds. GuDA helps us collect as much information about the game and the player’s actions as possible, while simultaneously allowing us to decide what that information means for the environmental effects, the reverb, the music, and finally, the mix.

Because of the flexibility of Decima’s nodegraph structure, we could tie systems together. This was key, because as soon as concepts such as day-night cycles were introduced to the game we could immediately tie sounds to it. All we needed was an input to GuDA with the current time. In fact, we had a whole day-night cycle system with ambience, music and mix completed before proper nightfall had been visually implemented in the game. The same thing applied to the dynamic weather system; we were able to work on the sound of rain in the game, and see how it reacted with birds and music, before the visual effects for rain were in place.

Those moments were quite exciting for us, and that excitement continues to this day. We keep on finding new information that we can feed into GuDA.

The visuals for the “Cauldrons” and ruins take a lot of influence from the world in The Matrix”, did the audio team have any strong audio inspirations when designing the machine world?

Bastian: The Cauldrons are basically fully automated, autonomous production facilities. They’re driven by artificial intelligence and operate independently. Our approach to finding a style for the Cauldrons was mainly driven by their visual aesthetics, which were the opposite of the natural environments in the outside world. The question we had to ask ourselves was, what would a place where no human had ever set foot sound like?

In the end we kept it rather functional, and designed the soundscape after what we imagined a high tech facility with no need for acoustic protection would sound like. Much of it sounds like how I imagine a factory at the start of the industrial revolution would have sounded, before the introduction of noise and safety requirements: all loud and mechanical. At the same time, there are a bunch of super-slick sounds in the Cauldrons that have an almost alien quality. When brought together, those different styles feel very coherent.


How did you deal with the massive variety available in weapons and outfits, from bows, slings and spears, to traps and different elements and parts to Aloy’s armor?

Lucas: Basically we dealt with it one by one, and with the help of several people. They were all completely different tracks – one track for outfits, one track for weapons, and so on. With the outfits, we began by working on the ‘basic’ set, which took us a long time. We made sure it worked for every situation – crouching, walking, running, jumping, climbing, special actions, et cetera. I think we started from scratch at least three times. Once we felt that it worked, we based the other sets around that basic set, which goes a lot faster, because you have all the hooks and roughly the kind of sound you want to achieve. If I remember correctly, pretty much all elements in the costumes were custom recorded materials, gathered throughout the project from studio recordings as well as recordings we did in our own little booths at Guerrilla.

I wasn’t involved in the process for weapons creation, but we did do a feedback session for each weapon, where the entire team would listen to the weapons and talk about what they liked and what didn’t click for them just yet. Often, that was because the artwork was still so much in flux that by the time we reviewed the weapon, something would have changed visually that wasn’t yet in the sound. In short: it involved a lot of iteration.

Anton: The bow-type sounds were something new for us. Coming off Killzone we mostly had ‘loud bang’ weapons, but this game was going to be largely driven by very quiet weapons. The first thing I decided to do was join an archery club to experience what it’s like to shoot arrows in real life. This gave me a reference point for how it should feel, not necessarily how it should sound.

Early in the production of Horizon Zero Dawn we also spent a lot of time finding the right feel for the bow with our intern of the time, Gijs Driesenaar.  We began by experimenting with the sound itself, and once we got that right, by emphasizing some of the key feelings of archery. For instance, in real life there is this critical balance when you release an arrow, which allows you to instantly know whether your shot was any good – even before the arrow has hit the target. It just feels right. We tried to emulate this by changing the sound of the bow string releasing and ‘firing’; if you have the right amount of tension when you release the arrow, it sounds much fatter and bigger than if you fire too soon.

Later on in the production, we learned that players would have the ability to modify Aloy’s weaponry. This added the challenge of retaining this carefully constructed feeling across a wide range of parameters. For instance, players could suddenly tense the bow much quicker. Fortunately we had built the assets in a really modular way, using lots of small bits of tension and lots of layers. And because we have a really flexible engine when it comes to passing along parameters to the sounds, we could take all the possible modifications the player could make and compensate for them in the sound design.


Aloy has an unlockable ability to slow down time with her “focus” when using a precision bow and arrow, this of course has the effect of slowing the audio, did you filter this and focus on certain aspects of the audio when time is slowed?

Lucas: Absolutely. Sound-wise, there is more happening than ‘just’ the sound being slowed down. We decided what was most important for Aloy to hear when she uses the focus, and altered the mix based on those priorities. In the game we have a lot of ‘mixing busses’, groups so to say, that we can affect during gameplay. For instance, there are several groups for dialog, several groups for environmental effects, foley, robots, weapons, music, and so on. For the focus mode, we put a spotlight on the robots.


Some actions such as gathering plants and crafting arrows, need to be repeated often, how did you avoid sound effects become too boring for such a long game?

Lucas: Basically, you listen to the game a lot. If a sound sticks out in-game, and you hear it often, chances are much greater that you will get annoyed by it. In the case of the plant-gathering sound effect, there are only two variations, which will make it sound repetitive in the long run. But it also serves as a UI-sound, something we want the player to instantly recognize, so in this case we’ve just made sure that the sound is relatively unobtrusive.


What foley or real life sounds turn up in unexpected places?

Lucas: There are a lot of colleagues all over the place. For instance, all the ‘Walla’ – basically, the unintelligible crowd reactions – in the festival was recorded with designers, coders and office staff, which was a blast. The voice of Baby Aloy was actually recorded with my then-6-month-old daughter Laura. One day it was just the two of us, so I put a microphone in front of her. It gave me a full range of happy cooing (when I was actively playing with her), to annoyance as I was doing the dishes, to frustrated crying as she tried to roll over on the ground and didn’t quite manage to do so yet. Of all the sound creating devices I gathered for Horizon, Laura was probably the most labor-intensive one.

Aloy’s swimming sounds were recorded in a swimming pool in Spain during a holiday. As sound designers, we often bring portable recording sets along on vacation to gather new and unusual source materials. The holiday was in March, when the water was still pretty cold, but at least there weren’t any tourists around!

Other than that, the sounds for Aloy’s costume use some weird props that you wouldn’t expect, ranging from magnets to video camera parts and small music boxes. We have a collection of weird objects in the studio to use and abuse for such purposes.


We’ve all seen the amazing video of a group of voice actors running around a small studio space sounding panicked, recording for Horizon Zero Dawn, how were all these sounds implemented in the game and applied to fit the character animations?

Bastian: The video you’re referring to was shot at a ‘Walla’ recording during the production, so the sounds weren’t intended to be synced to any particular animation. We shipped the game with almost three hours of cinematics, and there where quite a few scenes where we needed panicked crowd sounds for the background. We had a bunch of different sessions with smaller groups of voice actors, trying to cover as much in-game and cinematic scenes as possible.

Those sessions were fun for everyone, since they left quite a bit of creative freedom for the actors with regards to their performances, and allowed the director to play around with the group dynamics to achieve the best results. We even did some additional crowd recordings in-house, with colleagues. The crowd sounds during the Nora festival are all Guerrilla folks having a fun time with the audio team.


Horizon Zero Dawn utilizes a gorgeous art style, and hyper real environments, how did you design the soundscapes to reflect this art style?

Lucas: Luckily we had a small-ish test environment running early in the project cycle, including benchmark tests of what we wanted the environments to look like in the end. Having that material available helped a lot – we could make mockup movies, for instance, simply by putting sound effects against linear movies to define style. Once we knew what we wanted to achieve, we had to look at how to achieve that sound technically.

One thing that is very important in our soundscape is that we spend a lot of time trying to make it sound as lively as possible. It’s not just a looping ambience, but an interactive, ever-changing soundscape based on the animals that would likely live in those habitats. There are no ‘hard cut changes’, only small incremental changes that come about by spawning individual elements. For the environmental effects, there’s no trick to making them sound larger than life – they just have to sound natural and varied.

And again, just walking through the game a lot really helps you to hear the bigger picture. As a member of the develop team you have the option to make yourself invisible to robots. There were many times, at the end of an exhausting day, where I would just fire up the game and walk through the world for half an hour. Just listening to the sounds of the environments, the robots, the people, the music – and how they all worked together. It has a very relaxing effect. You know, until you start hearing that one thing that really sticks out, and then it’s back to business.

If you want to check out more of Horizon, here’s a great no commentary playthrough: 




We hope you enjoyed Sam’s interview, check out others in our Interviews section. Don’t forget to sign up to our Monthly Newsletter to make sure you don’t miss out on our reviews and interviews.

Sam Hughes

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