Last week we explored many aspects of search. Today, we'll focus on one aspect that's moving from trendy to norm: voice search.

Half of all searches are expected to happen orally by 2020, and 30% of searches will be done without using a screen, according to analysis cited in an infographic by marketing technology consultants Grazitti Interactive.

With increasing use of assistants such as Apple’s Siri, Google’s OK Google, Microsoft’s Cortana, Samsung's Bixby, and Amazon’s Alexa/Echo, many consumers have access to these types of devices—and more people are starting to use them as they discover the convenience of voice search.

But how does voice search affect SEO and SERPs?

The infographic illustrates the major factors that have a direct impact on SEO, and it can help you optimize for voice search. Take a look: