My Video Header Background Music is not playing

I tried to upload video for my header but unfortunately it's too big. So I just embedded a youtube file instead. But When you visit my site the video will automatically play but the sound is not working. I check youtube but when I play the video there the music is working. Can you help me with this? If there's no solution to this I'll just add the video at my welcome page but how would I make the video play automatically? Thanks, Eliez B