There are lots of different ways that we can use sound and VR. To create different kinds of effects and generally atmosphere and also to process sound and to change the way that people understand their environment. One of the main ways that we can do this is with sound effects. So sound effects, as I've already said, they give sonic characteristics to objects. They're usually short sounds that are produced by an object or collision of objects. So this might be the sound of a ball bouncing on different surfaces and it also might be the sound of a gunshot. And I think we're all aware that gunshots, particularly from movies, they don't sound much like real gunshots. They sound different because they're intended to produce a feeling of excitement. They might have a lot more base in them, for example, to make them vibrate more. Now importantly when we're talking about sound effects, we should try not to confuse sound effects with audio effect or audio filters. This is a problem because when people are talking about sound effects, sometimes they really mean audio effects. Audio effects are something different. Audio effects are things like delay, reverb, compression, flanging all these sorts of things. Now you can do all that kind of stuff in Unity. So it's very important you remember these two things aren't same. In Unity we refer to these sorts of things as audio filters. Another important kind of sound or type of sound that we use in VR is ambient sound. Ambient sound, it enhances the setting of your virtual world. It informs people in your virtual world about the kinds of materials they're surrounded by, the environment, how reflective it is can tell you a lot about how big it is. If it's very dull, maybe it's a very claustrophobic environment. Also your ambient sound can include things like rain, wind, low frequency hums for a spaceship atmosphere, crickets for nighttime, crowd noise, road noise, and anything else you can think of. Another core aspect of sound which happens in all virtual environments, or at least most of them, is speech. And it's really important to think about how you record and process speech. It changes an awful lot about what you're experiencing in an environment. Voice acting can be crucial in creating a believable virtual environment. And it's really common in VR, particularly with virtual characters, if your speech isn't recorded professionally or properly, if you don't use a nice microphone, then it's going to destroy your character. It's just not going to work. So pay attention. The quality of the recorded voice is going to be absolutely crucial so plan your voice recordings well in advance. Make sure people know what they're supposed to be saying and really take care to make sure that the kind of voice you're using fits the way you want to look and feel of a character to be. Another less obvious aspects of sound and virtual reality environments is music. Music mainly occurs in VR in two main ways. Either as a form of background music for atmosphere, such as a score or what we might think of as a score. And you can get lots of royalty free, rights free music on the Internet or you can make your own music. It can be synthesized sounds, or orchestral sounds, or music from the radio, if you have the rights in order to use them. Or it can also be in game music, in world music. For example sound which is happening on a radio or music which is happening on a radio inside an environment. There's a really good example of this in the Batman Arkham VR PSVR game where Bruce Wayne is sat at the piano and plays the piano and you can actually play a number of tunes on it with two fingers, which is not that satisfying, but it's an example of what we call, it's a form of diegetic music. Which means diegetic means within the diegesis, within the narrative. Whereas non-diegetic sound, the music in particular, is stuff which has nothing to do with the world itself. It's extraneous to the world but it adds atmosphere. So think about how you use music in these two ways. One thing that people often forget about, probably because they've not thought about it very much when making VR worlds, is realism. Now realism is really important. Realism is the way the elements of a scene inform you about the world. It's about how coherent things are. Now I want to be really, really clear about what I mean by the world. I don't mean the outside world or the real world. I mean the world of your VR environment. Realism has nothing to do with realistic. In fact trying to make a virtual reality environments or any kind of environment realistic isn't necessarily that interesting. For example, I might go to the pub and see people, I might be sitting down waiting for my friends, that's quite realistic but it's not interesting. I'm might be flying over some planets shooting civilians. That is not realistic but it is interesting. If the sound in my spacecraft, sounds like the same kind of sound I would expect, that might be realism, but it may not be anything like sound occurs in space, because there's no sound in space. So by realism what we mean is the way you use sound, and actually every element of a scene, to create an environment which is compelling and convincing in its own way, on its own terms. It has nothing to do with whether or not it is realistic. That's an important thing to bear in mind when considering the types of sounds that you choose. Don't choose a sound because it's realistic. Choose a sound or piece of music because it enhances the kind of realism that you want to portray.