How do I mute the audio from an embedded YouTube video? [duplicate]

This question already has an answer here:

• YouTube: How to present embed video with sound muted 2 answers

Example: http://ift.tt/2f8vfWC

I've been trying to wrap my head around how to mute the embedded YouTube video on my website. I've tried various scripts and methods and nothing I've tried works. Any help would be greatly appreciated.

The HTML embedded link looks like this:

<div class="video-background">
    <div class="video-foreground">
        <iframe src="https://www.youtube.com/embed/UGPuEDyAsU8?controls=0&showinfo=0&rel=0&autoplay=1&loop=1&=HD1080" frameborder="0" allowfullscreen></iframe>
    </div>
</div>

And the CSS method I've used for playing it in the background looks like this:

* { box-sizing: border-box; }
.video-background {
 background: #000;
 position: fixed;
 top: 0; right: 0; bottom: 0; left: 0;
 z-index: -99;
 }

.video-foreground,
.video-background iframe {
 position: absolute;
 top: 0;
 left: 0;
 width: 100%;
 height: 100%;
 pointer-events: none;
 }

 #vidtop-content {
 top: 0;
 color: #fff;
 }

@media (min-aspect-ratio: 16/9) {
.video-foreground { height: 300%; top: -100%; }
}

@media (max-aspect-ratio: 16/9) {
.video-foreground { width: 300%; left: -100%; }
}

@media all and (max-width: 600px) {
.vid-info { width: 50%; padding: .5rem; }
.vid-info h1 { margin-bottom: .2rem; }
}

@media all and (max-width: 500px) {
.vid-info .acronym { display: none; }
}