Echo / waves animation (CSS only). Demo: https://jsfiddle.net/AdonaiAraya/wcs8sdpt/

echo-animation-style.css

@-webkit-keyframes echo {
	0% {
		padding: 0;
		margin: 0;
		opacity: 1;
	}
	
	100% {
		padding: 50px;
		margin: -50px;
		opacity: 0;
	}
}

@keyframes echo {
	0% {
		padding: 0;
		margin: 0;
		opacity: 1;
	}
	
	100% {
		padding: 50px;
		margin: -50px;
		opacity: 0;
	}
}

.waves {
	position: absolute;
	left: 50%;
	top: 50%;
}

.wave {
	position: absolute;
	border: 2px solid #363636;
	border-radius: 50%;
	display: inline-block;
	padding: 0;
	
	animation-name: echo;
	animation-duration: 2s;
	animation-iteration-count: infinite;
	animation-timing-function: ease-out;
	
	-webkit-animation-name: echo;
	-webkit-animation-duration: 2s;
	-webkit-animation-iteration-count: infinite;
	-webkit-animation-timing-function: ease-out;
}

.wave:nth-of-type(2) {
	animation-delay: 0.4s;
	-webkit-animation-delay: 0.4s;
}

.wave:nth-of-type(3) {
	animation-delay: 0.8s;
	-webkit-animation-delay: 0.8s;
}

echo-animation-template.html

<div class="waves">
	<span class="wave"></span>
	<span class="wave"></span>
	<span class="wave"></span>
</div>