AudioAPI filter description

HTML

<audio controls="" preload="" src="add/src/here" autoplay=""></audio>

JavaScript

context = new AudioContext();
source = context.createMediaElementSource(document.getElementsByTagName('audio')[0]);

//Now we want to create a filter
filter = context.createBiquadFilter();
source.connect(filter); //and of course connect it
filter.type = "lowshelf"; //this is a lowshelffilter (try excuting filter1.LOWSHELF in your console)
filter.frequency.value = 95; //as this is a lowshelf filter, it strongens all sounds beneath this frequency
filter.gain.value = 30; //the gain with which it should increase

//now we want to connect that to the output
filter.connect(context.destination);