50ohm-contents-dl/contents/html/spektrum_sprachsignale.html

<html>
    <script src="https://www.50ohm.de/assets/jquery/3.7.1/jquery.min.js"></script>
    <script src="https://www.50ohm.de/assets/chartjs/4.4.1/chart.min.js"></script>

    <p>
    Durch Druck auf den nächsten Button, wird das Mikrofon des Browsers
    aktiviert. Danach kann man das Spektrum der eigenen Sprache betrachten.
    </p>
    <p>
        <button onclick="start()">Mikrofon Einschalten</button>
    </p>
    <p>
        <canvas id="Spectrum" style="max-height:200px;"></canvas>
    </p>
    Stärkste Amplitude bei der Frequenz $f$ = <div id="mainfrequency" style="display:inline-block;">0</div> Hz<br>

    <script type="text/javascript">

        spectrum = new Chart("Spectrum", {
            type: 'scatter',
            data: {
                labels: [],
                datasets: [
                    {
                        fill: false,
                        pointRadius: function(context) {
                            var index = context.dataIndex;
                            var value = context.dataset.data[index];
                            var max = Math.max.apply(null,context.dataset.data);
                            return value == max ? 6 : 0;
                        },
                        lineTension: 0.8,
                        showLine: true,
                        borderColor: function(context) { 
                            var index = context.dataIndex;
                            var value = context.dataset.data[index];
                            var max = Math.max.apply(null,context.dataset.data);
                            return value == max ? "#FF756D" : "#00AEDF";
                        },
                        data: [],
                    },
                ]
            },    
            options: {
                responsive:true,
                plugins: {
                    legend: {
                        display: false,
                    }
                },
                scales: {
                    y: {
                        min: 0,
                        max: 100,
                        ticks: {
                            callback: function(value, index, ticks) {
                                return value + "%";
                            }
                        }
                    },
                    x: {
                        min: 0,
                        max: 24000,
                        type: 'logarithmic',
                        title: {
                            display: true,
                            text: 'Frequenz'
                        },
                        ticks: {
                            callback: function(val, index) {
                                return val+"Hz";
                            },
                        }
                    }
                },
            }
        });

        var initialized = false;
        var binSize = 0;

        const getBigBinIndex = (frequencyBins) => {
            let biggestIndex = 0;
            frequencyBins.forEach((bin, index) => {
                if (bin > frequencyBins[biggestIndex]) {
                    biggestIndex = index;
                }
            });

            return biggestIndex;
        }

        const init = () => {
            var fftSize = 2048;
            var audioContext;

            var analyserNode;
            var frequencyData;
            var lastUpdate = 0;

            try {
                window.AudioContext = window.AudioContext || window.webkitAudioContext;
                audioContext = new AudioContext();
                binSize = (audioContext.sampleRate) / fftSize; // Bin Size in Hz
            } catch (e) {
                alert('Die Web Audio API wird in diesem Browser leider nicht unterstützt!');
            }

            const update = (timestamp) => {
                if (timestamp - lastUpdate > 50) {
                    analyserNode.getByteFrequencyData(frequencyData);
                    const bigBinIndex = getBigBinIndex(frequencyData);
                    const mainFrequencyStart = Math.floor(bigBinIndex * audioContext.sampleRate / fftSize);

                    const mainfrequencyDomElement = document.getElementById('mainfrequency');
                    mainfrequencyDomElement.textContent = mainFrequencyStart;

                    lastUpdate = timestamp;

                    // Reset all values:
                    spectrum.data.datasets[0].data = [];
                    spectrum.data.labels = [];

                    // Normalize Apmlitudes:
                    for(let i = 0; i < analyserNode.frequencyBinCount; i++) {
                        // Store Normalized Amplitude
                        spectrum.data.datasets[0].data.push((frequencyData[i]/255)*100); 
                        spectrum.data.labels.push(i*binSize);
                    }

                    // Update Graphs:
                    spectrum.update();
                }
                requestAnimationFrame(update);
            }

            // Acquire microphone access.
            navigator.mediaDevices.getUserMedia({
                audio: true,
                video: false
            }).then(stream => {
                var source = audioContext.createMediaStreamSource(stream);
                analyserNode = audioContext.createAnalyser(source);
                analyserNode.fftSize = fftSize;
                audioContext.resume();
                source.connect(analyserNode);
                console.log(analyserNode.frequencyBinCount);
                frequencyData = new Uint8Array(analyserNode.frequencyBinCount)
                window.requestAnimationFrame(update);
            });
        }
    
        const start = () => {
            if(initialized == false){
                init();
                initialized = true;
            }
        }
        
    </script>
</html>