I'm recording voice using recordRTC

let mediaConstraints = {
            video: false,
            audio: true
            };
            navigator.mediaDevices.getUserMedia(mediaConstraints).then(this.successCallback.bind(this), this.errorCallback.bind(this));
     successCallback(stream) {
        var options = {
        mimeType: "audio/wav",
        numberOfAudioChannels: 1,
        desiredSampRate: 16000,
        bufferSize: 16384,
        audioBitsPerSecond: 128000,
        recorderType: StereoAudioRecorder,
        };
    
        var StereoAudioRecorder = RecordRTC.StereoAudioRecorder;
        this.record = new StereoAudioRecorder(stream, options);
        this.record.record();

Audio is being recorded but the sound quality is not good there is lot of background noise, I want to record it with 16K sample rate.