Need desired format of .wav In Recoder.js

Question

I am using recorder.js to record audio. When I download .wav file it is 48KHz but I want in 16KHz, mono channel.

function init(config) {
            sampleRate = config.sampleRate; //to 16000
            numChannels = config.numChannels; //to 1
            initBuffers();
        }

It changes the recorded voice (like a voice of the robot).

Help me to get a voice in 16KHz, mono .wav file in a normal voice. (Thanx in Advance)

My Code Is Here