diff --git a/README.md b/README.md
index 713ccb7..edf0963 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,8 @@ PORT=8081 npm start
 - Custom STUN/TURN: gear icon → JSON override in `localStorage`, applied on
   next join. Server default comes from env (below).
 - Mute (M), deafen (D), per-peer volume, speaking indicators.
+- Voice capture uses mono 48 kHz Opus-oriented settings, a 64 kbps audio ceiling,
+  and periodic packet-loss, jitter, and RTT quality diagnostics.
 
 ## ICE configuration (server side)
 
@@ -49,5 +51,7 @@ service instead of depending on NAT hairpinning or direct candidate pairs.
   behind the preview ingress (use wss/TLS in front for real deploys).
 - No media server: N² mesh — fine for small rooms, needs SFU (mediasoup/livekit)
   beyond ~6–8 participants.
+- For larger rooms or consistently lower bandwidth, replace the mesh with an SFU;
+  the current quality tuning improves the P2P path but does not change its N² cost.
 - Text channels are decorative. No persistence, no rate limiting.
 - Screen-share negotiation storms on join/leave are expected at small scale.
diff --git a/public/app.js b/public/app.js
index 3150154..6d87f48 100644
--- a/public/app.js
+++ b/public/app.js
@@ -131,6 +131,78 @@ async function selectedIcePath(pc) {
   };
 }
 
+async function tuneAudioSender(sender) {
+  if (!sender?.getParameters || !sender?.setParameters) return;
+  const params = sender.getParameters();
+  if (!params.encodings?.length) params.encodings = [{}];
+  params.encodings[0].maxBitrate = 64000;
+  params.encodings[0].dtx = false;
+  params.encodings[0].priority = 'high';
+  await sender.setParameters(params);
+}
+
+function preferOpus(pc) {
+  const capabilities = globalThis.RTCRtpReceiver?.getCapabilities?.('audio');
+  const codecs = capabilities?.codecs || [];
+  const opus = codecs.filter((codec) => codec.mimeType?.toLowerCase() === 'audio/opus');
+  if (!opus.length) return;
+  const ordered = [...opus, ...codecs.filter((codec) => !opus.includes(codec))];
+  for (const transceiver of pc.getTransceivers()) {
+    if (transceiver.receiver?.track?.kind === 'audio' || transceiver.sender?.track?.kind === 'audio') {
+      try { transceiver.setCodecPreferences(ordered); } catch (err) {
+        captureRumIssue('Could not prefer Opus audio codec', 'WARNING', { error: err?.message || String(err) });
+      }
+    }
+  }
+}
+
+function monitorPeerQuality(peer) {
+  if (peer.qualityTimer) clearInterval(peer.qualityTimer);
+  peer.qualityTimer = setInterval(async () => {
+    const pc = peer.pc;
+    if (!pc || pc.connectionState !== 'connected' || !pc.getStats) return;
+    try {
+      const stats = await pc.getStats();
+      let inbound;
+      let outbound;
+      let remoteInbound;
+      stats.forEach((report) => {
+        if (report.kind !== 'audio' && report.mediaType !== 'audio') return;
+        if (report.type === 'inbound-rtp') inbound = report;
+        if (report.type === 'outbound-rtp') outbound = report;
+        if (report.type === 'remote-inbound-rtp') remoteInbound = report;
+      });
+      const packets = (inbound?.packetsReceived || 0) + (inbound?.packetsLost || 0);
+      const lossRatio = packets > 20 ? (inbound.packetsLost || 0) / packets : 0;
+      const jitterMs = (inbound?.jitter || 0) * 1000;
+      const rttMs = (remoteInbound?.roundTripTime || 0) * 1000;
+      const issue = lossRatio >= 0.05 || jitterMs >= 80 || rttMs >= 500;
+      if (issue && (!peer.lastQualityNotice || Date.now() - peer.lastQualityNotice > ICE_NOTICE_INTERVAL)) {
+        peer.lastQualityNotice = Date.now();
+        const details = `quality degraded (loss ${Math.round(lossRatio * 100)}%, jitter ${Math.round(jitterMs)}ms${rttMs ? `, RTT ${Math.round(rttMs)}ms` : ''})`;
+        toast(`${peer.name}: ${details}`, 'warn');
+        captureRumIssue('WebRTC audio quality degraded', 'WARNING', {
+          peerId: peer.id,
+          peerName: peer.name,
+          lossRatio,
+          jitterMs,
+          rttMs,
+          packetsReceived: inbound?.packetsReceived,
+          packetsLost: inbound?.packetsLost,
+          bytesReceived: inbound?.bytesReceived,
+          bytesSent: outbound?.bytesSent,
+          path: peer.icePath?.path,
+        });
+      }
+    } catch (err) {
+      captureRumIssue('Could not inspect WebRTC audio quality', 'WARNING', {
+        peerId: peer.id,
+        error: err?.message || String(err),
+      });
+    }
+  }, 5000);
+}
+
 function playRetroCue(name) {
   const ctx = S.audioCtx;
   if (!ctx) return;
@@ -191,7 +263,14 @@ function effectiveIce() {
 }
 
 function microphoneConstraints(deviceId = localStorage.getItem(LS_AUDIO_INPUT)) {
-  const audio = { echoCancellation: true, noiseSuppression: true, autoGainControl: true };
+  const audio = {
+    echoCancellation: true,
+    noiseSuppression: true,
+    autoGainControl: true,
+    channelCount: 1,
+    sampleRate: 48000,
+    sampleSize: 16,
+  };
   if (deviceId) audio.deviceId = { exact: deviceId };
   return { audio };
 }
@@ -561,6 +640,8 @@ function makePeerRecord(p) {
     resetAttempts: 0,
     lastIceNotice: null,
     icePath: null,
+    qualityTimer: null,
+    lastQualityNotice: 0,
     els: {},
   };
 }
@@ -658,16 +739,24 @@ function ensurePC(peer, initiator) {
           error: err?.message || String(err),
         });
       });
+      monitorPeerQuality(peer);
     }
   };
   pc.ontrack = (ev) => onRemoteTrack(peer, ev);
 
   // send my mic; if I have none, ask to receive theirs
   if (S.micStream) {
-    for (const track of S.micStream.getAudioTracks()) pc.addTrack(track, S.micStream);
+    for (const track of S.micStream.getAudioTracks()) {
+      const sender = pc.addTrack(track, S.micStream);
+      tuneAudioSender(sender).catch((err) => captureRumIssue('Could not tune Opus audio sender', 'WARNING', {
+        peerId: peer.id,
+        error: err?.message || String(err),
+      }));
+    }
   } else {
     pc.addTransceiver('audio', { direction: 'recvonly' });
   }
+  preferOpus(pc);
 
   // send my screen share if I am currently sharing when this peer connects
   if (S.sharing) {
@@ -710,6 +799,7 @@ function recreatePeerConnection(peer, { announce }) {
     send({ type: 'reset', to: peer.id });
   }
   if (peer.pc) { try { peer.pc.close(); } catch {} }
+  if (peer.qualityTimer) { clearInterval(peer.qualityTimer); peer.qualityTimer = null; }
   peer.pc = null;
   peer.makingOffer = false;
   peer.ignoreOffer = false;
@@ -754,6 +844,7 @@ async function onCandidate(peer, candidate) {
 
 function destroyPeer(peer) {
   if (peer.pc) { try { peer.pc.close(); } catch {} peer.pc = null; }
+  if (peer.qualityTimer) { clearInterval(peer.qualityTimer); peer.qualityTimer = null; }
   detachSpatial(peer);
   if (peer.audioEl) {
     try { peer.audioEl.pause(); peer.audioEl.srcObject = null; } catch {}