Binaural audio was included in Hunt: Showdown when we released on SteamEarly Access back in February 2018. Since then we've been overwhelmed by positive feedback from the community about what Hunt's audio adds to the game. It's really been a great enhancement for Hunt's soundscape.
Today, I want to explain a little more about how it all works.
HRTF is short for Head Related Transfer Function. Essentially, it allows for directional hearing on regular stereo headphones. “Directional" means that you are able to recognize where exactly sounds are coming from. So not only will you be able to tell if a sound is coming from the left or right, but also if one is coming from the front or back, as well as from above or below. 3D spatial audio mimics natural human aural perception. Aka binaural audio.
At this point, a lot of people ask, well isn't that just stereo sound?
Yep! Stereo is the natural way we perceive sound in the real world - we only have two ears!
Our brains can distinguish whether a sound source is behind or in front of us, above or below us, or to the left or the right. And it has to do with - drumroll - the way sound waves propagate through air, and how they permeate and bend around objects. The shape of our ears, our head, and our shoulders – each of these things filters every sound wave, and adds a unique sound “color" before the sound wave even reaches our eardrums. This “color-coded data" is passed on to our brain, which is a master of processing and decoding this stuff in no time. It's been trained to do so all its life.
Directional hearing is natural to us, and it's crucial for our survival. Hunters and gatherers thousands of years ago needed to rely on their senses in order to react quickly in dangerous situations, for example. It's the same today: We learn very early to not cross the street when we hear the sound of a car approaching; by the time you see the bus, it could be too late. Hearing it coming can be lifesaving.
When perceiving sound, our body acts as an array of channels and filters, including the time dilation between the left and right ear – which all in all modulates the sound upon the direction it comes from. In the past couple of decades, the industry started being able to simulate this effect in video games.
HRTF for video games came up in the 1990s, but required hardware acceleration, and somehow remained a rather exotic sound feature. However, we've seen a revival recently alongside virtual reality, where binaural audio is an absolute must-have. But traditional 3D games are also starting to use the effect again, especially in cases where 3D perception should go beyond visuals in order to enhance game readability and emotional aspects like tension and immersion. Without a doubt HRTF helps increase the believability of a game's soundscape - and for that matter, the whole game!
After shipping VR titles like The Climb and Robinson: The Journey with binaural audio, we simply had to give it a try in Hunt: Showdown, too.
How does HRTF work?
HRTF-Plugins trick the ear by utilizing the positional game data to add that extra sound filtering in runtime. Imagine a sphere around the player where every single dot owns a subtly unique blend of sound filters, plus left-right time dilation, which the brain then connects to the direction we want it to perceive.
In the end, it isn't your ears that we're tricking: it's your brain.
Tricking the brain is not an easy task. Everybody has a slightly different head and ear shape, individual taste, and unique expectations about how a game should sound. Pulling this off requires a significant amount of time and resources that go into programming, testing, designing, bug-fixing, and re-iterating on the behavior of the filters and parameters. Our intention is to approximate the expectations of the average person, which we hope will make it work for the largest possible number of players. Even if you're not “average", you're very likely to get the effect instantly, as soon as there is visual reference.
After a few rounds playing Hunt, you should be pretty much “locked in" with the binaural sound mechanic. We hope to hit the right sound recipe for as many people as possible with our own HRTF-Plugin CrySpatial, which is continuously being optimized.
Our goal is to turn the player's ears into a second pair of eyes. In Hunt, being able to read the environment by listening can give you a real advantage – and make immersion all the more intense. So when you hear the scream of the Hive in the distance, or a gunshot from an enemy player, the binaural audio can help you locate those threats and stay alive a little bit longer.
Check back on the blog this Friday for tips for improving your Hunt audio experience!