Hi Alexis, 

By default unbounce turned off the  sound for a reason. You might want to read it from this thread. I hope that makes sense. They don’t have the option yet to turn it on, I hope they can have it in the future 😃

Unfortunately, Video backgrounds currently do not include sound.

Reference - http://documentation.unbounce.com/hc/en-us/articles/203660914-Adding-Video

Hi Alexis

You can have a video in header section which auto plays(if you choose) with sound when

user loads the page. Click on the embed video button on left side tool bar and drag it on

the page where you want to have the video. On video box double click to open it and

add the following code:

    <iframe width="420" height="315"

src="https://www.youtube.com/embed/XGSy3_Czz8k?controls=0">

</iframe>

Replace the src with url of your you tube video.

Parameters added in above code:

autoplay

Value 0 (default): The video will not play automatically when the player loads.

Value 1: The video will play automatically when the player loads.

loop

Value 0 (default): The video will play only once.

Value 1: The video will loop (forever).

controls

Value 0: Player controls does not display.

Value 1 (default): Player controls display.

You can also refer to Unbounce documentation for embeding video,

w3school, google documentation embed youtube