A CodePen by Jack Rugile. CSS3 Pseudo Sound Bars

index.html

<h1>CSS3 Pseudo Sound Bars</h1>
<div id="bars">
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
    <div class="bar"></div>
</div>

style.css

h1 {
    color: #555;
    font: bold 12px 'helvetica neue', helvetica, arial, sans-serif;
    left: 0;
    margin: 20px 0 0 0;
    position: absolute;
    top: 50%;
    text-align: center;
    width: 100%;   
}

#bars {
    height: 30px;
    left: 50%;
    margin: -30px 0 0 -20px;
    position: absolute;
    top: 50%;
    width: 40px;
}

.bar {
   background: #666;
    bottom: 1px;
    height: 3px;
    position: absolute;
    width: 3px;      
    animation: sound linear infinite alternate;
}

@keyframes sound {
    0% {
       opacity: .35;
        height: 3px;            
    }
    100% {
        opacity: 1;       
        height: 28px;        
    }
}

.bar:nth-child(1)  { left: 1px; animation-duration: 474ms; }
.bar:nth-child(2)  { left: 5px; animation-duration: 433ms; }
.bar:nth-child(3)  { left: 9px; animation-duration: 407ms; }
.bar:nth-child(4)  { left: 13px; animation-duration: 458ms; }
.bar:nth-child(5)  { left: 17px; animation-duration: 400ms; }
.bar:nth-child(6)  { left: 21px; animation-duration: 427ms; }
.bar:nth-child(7)  { left: 25px; animation-duration: 441ms; }
.bar:nth-child(8)  { left: 29px; animation-duration: 419ms; }
.bar:nth-child(9)  { left: 33px; animation-duration: 487ms; }
.bar:nth-child(10) { left: 37px; animation-duration: 442ms; }​