navigator.mediaDevices
                    .getUserMedia({
                        video: false,
                        audio: {
                            echoCancellation: true,
                            noiseSuppression: true,
                            autoGainControl: false,
                        },
                    })
                    .then((stream) => {
                        var aCtx = new (window.AudioContext || window.webkitAudioContext)();
                        var analyser = aCtx.createAnalyser();
                        var microphone = aCtx.createMediaStreamSource(stream);
                        microphone.connect(analyser);
                        analyser.connect(aCtx.destination);
                    })
                    .catch((e) => alert(e.name + ': ' + e.message));

full pwa src: https://github.com/sentienhq/Hearing-Aid