Reading this post: https://blog.hubspot.com/marketing/elements-of-modern-web-design-list, hubspot suggests adding "auto play" videos to your website. In addition to being rude and annoying, it's already been shown that it's just plain bad practice: http://www.punkchip.com/autoplay-is-bad-for-all-users/.
As someone pointed out, the example site that hubspot points to does not play sound while it autoplays. With or without sound, this is still an egregious practice as many folks are still on metered data plans (especially on mobile). Just don't do it.