Get frequency of current period of audio

This is the code that i have been using to get frequency data of current time period of song. However its outputting same frequency again and again.

var audio = new Audio();
audio.src = 'anaconda.mp3';

var ctx = new webkitAudioContext(),
    source;

source = ctx.createMediaElementSource(audio);
var analyser = ctx.createAnalyser();
source.connect(analyser);
analyser.connect(ctx.destination);

draw();

function draw() {

    for (var i = 0; i <= audio.duration; i++) {
        audio.currentTime = i;
        getFrequency();
    }

}

function getFrequency() {

    analyser.fftSize = 32;
    var bufferLength = analyser.fftSize;
    var freqData = new Uint8Array(bufferLength);
    analyser.getByteTimeDomainData(freqData);

    console.log(freqData);
}

This is the output that i am getting in a loop:

[128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128]