diff --git a/web/chat.html b/web/chat.html
index 204c6a8..9bd4811 100644
--- a/web/chat.html
+++ b/web/chat.html
@@ -232,7 +232,7 @@
     <span class="note" id="rx-label" style="min-width:3rem; text-align:right">—</span>
   </div>
   <p class="note">
-    a 440/441&nbsp;Hz stereo carrier is generated locally. each frame swings the
+    a 440&nbsp;Hz carrier is generated locally. each frame swings the
     output gain MARK (0.80) ↔ SPACE (0.20) per bit. the modulated audio is the
     outbound WebRTC track for every connected peer. mic stays off.
   </p>
@@ -800,7 +800,9 @@ async function startCarrier() {
   if (audioCtx.state === 'suspended') await audioCtx.resume();
   oscL = audioCtx.createOscillator(); oscR = audioCtx.createOscillator();
   oscL.type = 'sine'; oscL.frequency.value = 440;
-  oscR.type = 'sine'; oscR.frequency.value = 441;
+  /* same freq on both channels: the codec is mono (G.711), so a 440/441 split
+   * would downmix into a 1 Hz beat that swamps the amplitude levels. */
+  oscR.type = 'sine'; oscR.frequency.value = 440;
   gainL = audioCtx.createGain(); gainR = audioCtx.createGain();
   gainL.gain.value = ZEBRA_VOL_MARK;
   gainR.gain.value = ZEBRA_VOL_MARK;
@@ -1627,7 +1629,7 @@ $('btn-audio').addEventListener('click', async () => {
     $('dot-audio').className = 'dot on';
     $('audio-status').textContent = 'online';
     $('btn-audio').disabled = true;
-    logLine('sys', 'carrier started — modulated stereo at 440/441 Hz');
+    logLine('sys', 'carrier started — modulated 440 Hz');
   } catch (e) {
     logLine('err', 'carrier failed: ' + e.message);
   }