[MUSIC] By now you should have a pretty good understanding of the technical requirements around sound. What it is, how we measure it, how you perceive it, and also how it's stored. But how do we use it? What's it useful for? So the first thing I would say is that sound is much more useful than many people think. When you're making a game or a VR world or even other kinds of media like film, often people think about sound at the end. This is a mistake, you should think about sound in the same way that you think about images, graphics, and all forms of visual representation. A really bad sound can make a really good image look terrible. Likewise, a really really good sound can make a really really bad image look great. Now this happens because of lots of cognitive illusions that occur when people combine sounds and images the way that sounds and images combine in the brain, changes the way that you perceive images and sound. And there's lots of evidence for this. What this means practically for you is that the more time you put into considering how sound is affecting your environment and people's perception of it, the better your work's going to be. It's good to think about the kinds of things you can do with sound creatively, so that's what we're going to do. Let's imagine that we want to affect the way people perceive the size of something using a sound. You can use the frequency content of the sound to change how people perceive the physical properties of an object. For example, a very very large firework will make a big, loud, low frequency bang [SOUND], and a really really really small firework is going to go [SOUND]. Even if it's the same size on the screen, that sound will fool you into making decisions or convince you about decisions that lead you to understand where the object is, how big it is, how much it might weigh, things like that. If I kick a metal bucket, for example, and that metal bucket doesn't move and has dull thud, I assume it's very heavy and has something in it. If I kick a metal bucket and it makes a tiny, tiny ping noise, right? And as it rattle, even if it doesn't move, the brain might assume that it's very light. So the way that we use sound effects colors our perception of the size and the weight of objects even when they look exactly the same on the screen. As I've already indicated, the speed of sound and also the way that a particular sound source is traveling and also the ambience of the environment, have a big impact on what you can do. So Doppler effect will indicate that something is going very quickly towards you. And also reverberation can make you think that you're in one environment or another. For example, you might suddenly want to make people feel like they're underwater. Now it can be very very expensive to create a computer graphic effect that places you underwater, also the lighting may be very dark, but if you just use the sound to dull the high frequencies, you can create the effect of an underwater sound. [MUSIC]