Sound Design Note
Audio is important in many forms of storytelling. George Lucas once said “Sound is half of the experience” It is even truer when it comes to Virtual Reality because the sound in VR can directly affect the immersion of the experience. For example, if we pick up a bottle in VR and drop it on the ground and it creates no sound or the sound does not match our expectations, then our subconscious will tell us immediately that there is something wrong in the virtual world we are trying to create. Because sound doesn’t work like that in our daily lives, we have to make sure the audio experience is intuitive enough that the audience won’t disconnect from believing in the virtual world. Without a proper audio design, the narrative experience will lose its charm and the world won’t be as convincing.
While helping to create the interactive narrative of The Price of Freedom, I have come up with some ideas about what works and what doesn’t. Consider this as a post-mortem for The Price of Freedom, and I am eager to share with you some of the lessons that I learned.
The Price of Freedom is an interactive VR story based on the declassified true event of Project MK Ultra. Project MK Ultra was a highly controversial project that ran from the 1950s to the 1970s in which the CIA experimented with several methods including using LSD to brainwash its subjects. In the story, you take the role of a CIA agent and are given a task to kill Ben Miller, a radical who broke into CIA facilities and stole top-secret chemical weapons research. By exploring the environment, the player discovers the true reason for their mission and who they really are.
Audio design for interactive experiences can be categorized into four elements: Sound Effects, Music, Ambience, and Dialogue. But how should we prioritize making these elements and where should we place them when it comes to VR?
1. The Importance of Collision & Interaction Sound
Integrating collision and interaction sounds into the experience in a very early stage of the production is a good idea. This can not only help the designer or developer of the team have a more concrete sense of how the virtual world they designed feels, but also help audio professionals examine how things actually sound in the VR environment so that we can spot potential problems and make changes as early as possible.
At first, when creating the prototype of The Price of Freedom, there was only one collision sound clip for each object in the scene. Here is an example of how it sounded.
The sound experience needs more variation to be closer to reality in order for us to feel comfortable. Lacking diversity breaks the immersion because we don’t find it natural. So here are the solutions:
At Construct Studio, we designed a sound system that had two features. First, we created a list of common material sound folders like wood, metal, paper, stone, and so on. Then we assigned them to every object based on their features. Second, the system receives the info of how strong the object’s collision force is each time it collides and then divided them into three groups: light, medium, and heavy. Each group has a list of sound clips that will be selected to play randomly each time when the sound is triggered. On top of that, we also added the pitch variation to the sound clips to make sure that each time it would sound slightly different.
We have to apply this sound system to almost every object in the scene. Since the player has the freedom to interact with almost everything they want in the scene, we have to make sure that everything they touch has satisfying sound feedback that won’t break the immersion. But if there are so many audio effects around the players, how are they going to receive more important information and find out what the story is about in VR?
2. Using Sound to Tell Story
When it comes to using audio to tell interactive narratives in VR, there is one concept to keep in mind: Indirect Control. It is a technique to use design to guide the player to certain expected actions without letting them realize the fact that they are being guided.
A well-designed audio experience is a great opportunity for indirect control since audio has several key features that can be used to guide the player. First, it sets the time and space of the experience for the player. In The Price of Freedom, for example, we have a radio in a scene that plays the music from the 60s, and a TV that broadcasts John F. Kennedy’s inauguration speech so that the players can clearly get it that they are in a specific time period. In this case, the 60s in the United States.
Also, apart from the instructional dialogues that directly guide the player on what to do, we also have reel-to-reel tapes with dialogue that can not only guide the player to focus on the specific area of the space but also provides fragments of the story as reinforcement. The tapes, along with other elements like letters, documents, and pictures remind the player of the story over and over again. So that even if they miss some of the information, they are still able to have an overall understanding of the narrative.
3. Spatial Audio Placement in VR
Now that we have created all the sound files, how should we place them in a VR environment? We want to make the player feels like they are actually in that space but, at the same time, we try to reinforce the clarity of some audio cues and make sure the player won’t miss it. In general, we separated them into two groups: the first group is the one where audio is placed in fixed locations in the environment; audio from the second group is placed in relative locations based on the player.
The first group includes our ambiance sound, collision/ interaction sound, diegetic music, and some of the dialogue. It attaches the sound to either a certain object or a place in the space that helps to create the audio environment of the player. Take our surrounding ambiance environmental sound as an example: We designed a 5 speakers system for each room, attached each mono sound file to each speaker, and place them in the space to simulate how we set 5.1 speakers in the real world.
The second group of sounds; however, will move to correspond to the player’s location. This is sometimes called “head-locking” the audio. Examples include some of the dialogue and some of the non-diegetic music and audio from the cutscenes. This group is for the purpose of making sure the player would receive the full information of the audio content. Take the voiceover as an example: we have a voice from the doctor’s character that gives you orders about what you should do throughout the experience. We put the voice audio source right behind the player’s head all the time. This setting not only enables the players to always be able to get clear information from the same orientation but it also matches the setting of the story.
4. Mixing in VR
Now we have all the sound in place in VR. How are we going to mix it?
We figured that it would be easier for us to manage all audio sources by putting them into bigger groups (SFX, Music, Dialogue, and Ambience), assigning the groups to individual channels in the Unity mixer, and mixing based on the group instead of individual files. Of course, for the files that are grouped into one channel, I have already adjusted their relative volume between each other in DAW first before putting them into the game engine. That being said, it is still very important to check your mix in VR because the audio you heard in DAW is definitely going to sound different in VR. it’s not a one-time thing, but a back and forth process.
To sum up, working on collision and interaction sounds and putting them in the prototype as early as possible helps the developing process for both designers and audio professionals. Understanding how to use audio as a guide the players enriches the interactive storytelling by addressing information to the players and manipulating their state of mind. Adopting the concept of signature music also enables the players to identify with the characters and plots in the story and have a more memorable experience. Last but not least, a good spatial audio placement strategy and mixing technique not only enhances the efficiency of the audio pipeline but also gives a more immersive result.