feat: implement RMS noise gate and enhance microphone capture settings for improved audio quality

docs/superpowers/plans/2026-05-13-web-mic-noise-suppression.md

@@ -0,0 +1,163 @@
+# Web Mic Noise Suppression Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Reduce background noise from the browser microphone before audio is sent to Discord.
+
+**Architecture:** Use native browser audio constraints for echo cancellation, noise suppression, and auto gain control at `getUserMedia` capture time. Add a lightweight RMS noise gate inside the existing `onaudioprocess` transmit loop so quiet background noise becomes silence before PCM is sent over WebSocket.
+
+**Tech Stack:** Browser MediaDevices API, Web Audio API, plain JavaScript in `public/index.html`, existing Bun/TypeScript verification scripts.
+
+---
+
+## File Structure
+
+- Modify `public/index.html`: update mic capture constraints and add local RMS noise gate constants/helpers inside the existing script.
+- No new dependencies.
+- No server changes required.
+
+---
+
+### Task 1: Enable Browser-Level Audio Processing
+
+**Files:**
+- Modify: `public/index.html`
+
+- [ ] **Step 1: Update microphone constraints**
+
+Replace:
+
+```js
+const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+```
+
+With:
+
+```js
+const stream = await navigator.mediaDevices.getUserMedia({
+    audio: {
+        echoCancellation: true,
+        noiseSuppression: true,
+        autoGainControl: true,
+        channelCount: 1,
+        sampleRate: SAMPLE_RATE,
+    },
+});
+```
+
+- [ ] **Step 2: Run lint**
+
+Run:
+
+```bash
+bun run lint
+```
+
+Expected: exits `0`.
+
+---
+
+### Task 2: Add Lightweight RMS Noise Gate
+
+**Files:**
+- Modify: `public/index.html`
+
+- [ ] **Step 1: Add threshold constants near audio constants**
+
+Add after:
+
+```js
+const CHANNELS = 1;
+```
+
+This code:
+
+```js
+const NOISE_GATE_THRESHOLD = 0.01;
+const NOISE_GATE_HOLD_FRAMES = 3;
+let noiseGateHold = 0;
+```
+
+- [ ] **Step 2: Add RMS helper function before `startStreaming()`**
+
+Add before:
+
+```js
+async function startStreaming() {
+```
+
+This function:
+
+```js
+function calculateRms(samples) {
+    let sum = 0;
+    for (let i = 0; i < samples.length; i++) {
+        sum += samples[i] * samples[i];
+    }
+    return Math.sqrt(sum / samples.length);
+}
+```
+
+- [ ] **Step 3: Apply gate before PCM conversion**
+
+Replace:
+
+```js
+const inputData = e.inputBuffer.getChannelData(0);
+const pcmData = new Int16Array(inputData.length);
+for (let i = 0; i < inputData.length; i++) {
+    pcmData[i] = Math.max(-1, Math.min(1, inputData[i])) * 32767;
+}
+socket.send(pcmData.buffer);
+```
+
+With:
+
+```js
+const inputData = e.inputBuffer.getChannelData(0);
+const rms = calculateRms(inputData);
+if (rms >= NOISE_GATE_THRESHOLD) {
+    noiseGateHold = NOISE_GATE_HOLD_FRAMES;
+} else if (noiseGateHold > 0) {
+    noiseGateHold--;
+}
+
+const pcmData = new Int16Array(inputData.length);
+for (let i = 0; i < inputData.length; i++) {
+    const sample = noiseGateHold > 0 ? inputData[i] : 0;
+    pcmData[i] = Math.max(-1, Math.min(1, sample)) * 32767;
+}
+socket.send(pcmData.buffer);
+```
+
+- [ ] **Step 4: Reset gate on stop**
+
+Add inside `stopStreaming()` after:
+
+```js
+isStreaming = false;
+```
+
+This line:
+
+```js
+noiseGateHold = 0;
+```
+
+- [ ] **Step 5: Run verification**
+
+Run:
+
+```bash
+bun run test && bun run typecheck && bun run lint && bun run build
+```
+
+Expected: all commands exit `0`.
+
+---
+
+## Self-Review
+
+- Spec coverage: Browser native noise suppression and JS noise gate are both covered.
+- Placeholder scan: No placeholders or TODOs.
+- Type consistency: Uses existing `SAMPLE_RATE`, `CHANNELS`, and `onaudioprocess` pipeline.

public/index.html

@@ -175,6 +175,9 @@
         // Optimized settings (1/4 bandwidth compared to 48k Stereo)
         const SAMPLE_RATE = 24000;
         const CHANNELS = 1;
+        const NOISE_GATE_THRESHOLD = 0.01;
+        const NOISE_GATE_HOLD_FRAMES = 3;
+        let noiseGateHold = 0;
 
         function initWebSocket() {
             if (socket && (socket.readyState === WebSocket.OPEN || socket.readyState === WebSocket.CONNECTING)) return;
@@ -258,9 +261,25 @@
             }
         };
 
+        function calculateRms(samples) {
+            let sum = 0;
+            for (let i = 0; i < samples.length; i++) {
+                sum += samples[i] * samples[i];
+            }
+            return Math.sqrt(sum / samples.length);
+        }
+
         async function startStreaming() {
             try {
-                const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+                const stream = await navigator.mediaDevices.getUserMedia({
+                    audio: {
+                        echoCancellation: true,
+                        noiseSuppression: true,
+                        autoGainControl: true,
+                        channelCount: 1,
+                        sampleRate: SAMPLE_RATE,
+                    },
+                });
                 isStreaming = true;
                 toggleBtn.innerText = 'Stop Transmitting';
                 toggleBtn.className = 'btn btn-danger';
@@ -281,9 +300,17 @@
                     if (!isStreaming || socket.readyState !== WebSocket.OPEN) return;
                     
                     const inputData = e.inputBuffer.getChannelData(0);
+                    const rms = calculateRms(inputData);
+                    if (rms >= NOISE_GATE_THRESHOLD) {
+                        noiseGateHold = NOISE_GATE_HOLD_FRAMES;
+                    } else if (noiseGateHold > 0) {
+                        noiseGateHold--;
+                    }
+
                     const pcmData = new Int16Array(inputData.length);
                     for (let i = 0; i < inputData.length; i++) {
-                        pcmData[i] = Math.max(-1, Math.min(1, inputData[i])) * 32767;
+                        const sample = noiseGateHold > 0 ? inputData[i] : 0;
+                        pcmData[i] = Math.max(-1, Math.min(1, sample)) * 32767;
                     }
                     socket.send(pcmData.buffer);
 
@@ -300,6 +327,7 @@
 
         function stopStreaming() {
             isStreaming = false;
+            noiseGateHold = 0;
             if (processor) processor.disconnect();
             if (audioContextTransmit) audioContextTransmit.close();
             toggleBtn.innerText = 'Start Transmitting';