diff --git a/docs/systems/sounds.md b/docs/systems/sounds.md
index e7d59a8c..f1f8ea03 100644
--- a/docs/systems/sounds.md
+++ b/docs/systems/sounds.md
@@ -1,14 +1,19 @@
 # System Sounds
 
-Single source of truth for the in-app audio cue layer. Every file in
-`packages/web/public/sounds/` is wired to exactly one event with a defined
-audience.
+Single source of truth for the in-app audio cue layer. Files live in
+`packages/web/public/sounds/` as **Ogg Vorbis** (`.ogg`). Most cues are wired
+to exactly one event; the two `stream_user_*` cues are dual-audience (see
+their rows). All cues are self-authored (no third-party/Discord audio).
 
 Source files:
 - Controller: `packages/web/src/components/voice/SoundController.tsx`
+- Viewer-action cues: `packages/web/src/components/voice/StreamTile.tsx`
+  (`handleViewerWatchToggle`)
 - Audio engine: `packages/web/src/audio/AudioManager.ts`
 - Pure helpers: `packages/web/src/utils/notificationFilters.ts`,
-  `packages/web/src/utils/streamWatchProtocol.ts`
+  `packages/web/src/utils/streamWatchProtocol.ts`,
+  `packages/web/src/utils/voiceSoundTransitions.ts` (mute/deafen cue selection)
+- SFX volume: `packages/web/src/utils/sfx.ts` (`getSfxVolume`, `SFX_BASE_VOLUME`)
 - Settings: `packages/web/src/stores/voiceStore.ts`
   (`soundEffectVolume`, `messageSoundAllChannels`),
   `packages/web/src/components/modals/settingsPanels/VoicePanel.tsx`
@@ -19,22 +24,22 @@ Source files:
 
 | File | Event | Audience | Trigger |
 |---|---|---|---|
-| `mute.mp3` | "I am now muted" (any cause) | self | `effectiveMuted` flips true while LK-connected. Effective = self toggle ∪ space-mute ∪ permission-mute. |
-| `unmute.mp3` | "I am no longer muted" | self | `effectiveMuted` flips false while LK-connected. |
-| `deafen.mp3` | "I am now deafened" | self | `effectiveDeafened` flips true while LK-connected. |
-| `undeafen.mp3` | "I am no longer deafened" | self | `effectiveDeafened` flips false while LK-connected. |
-| `camera_on.mp3` | self camera enabled | self | `voiceStore.isCameraOn` flips true. |
-| `camera_off.mp3` | self camera disabled | self | `voiceStore.isCameraOn` flips false. |
-| `user_join.mp3` | someone (incl. self) joined the voice channel | everyone in call | self `isLiveKitConnected` flips true OR a remote participant appears in `participants[]`. |
-| `user_leave.mp3` | a remote participant left voice | everyone in call (excl. the leaver) | a userId disappears from `participants[]`. Suppressed for self (uses `disconnect.mp3`) and during teardown (`justDisconnected` guard). |
-| `disconnect.mp3` | self left voice | self | `isLiveKitConnected` flips false. |
-| `call_ringing.mp3` | incoming DM call (loop) | callee | `voiceStore.incomingCall !== null`. Loops while ringing; cleaned up on accept/reject/timeout. |
-| `call_calling.mp3` | outgoing DM call (loop) | caller | `voiceStore.outgoingCall !== null`. |
-| `stream_started.mp3` | any participant started a screen share | everyone in call (incl. the streamer) | a userId appears in the `participants[].isScreenSharing` set. |
-| `stream_ended.mp3` | any participant stopped a screen share | everyone in call | a userId leaves the `participants[].isScreenSharing` set. |
-| `stream_user_joined.mp3` | a viewer started watching **my** stream | streamer only | `streamWatchers[selfUserId]` gains a watcher identity. |
-| `stream_user_left.mp3` | a viewer stopped watching **my** stream | streamer only | `streamWatchers[selfUserId]` loses a watcher identity. Suppressed for the entire watcher set when self-stream-end fires (see Mechanism Notes). |
-| `message.mp3` | new chat message arrived | self | `shouldPlayMessageSound` returns true (DM channel OR content mentions any of the user's self-ids). User can flip `messageSoundAllChannels` to fire on every channel. |
+| `mute.ogg` | "I am now muted" (any cause) | self | `effectiveMuted` flips true while LK-connected. Effective = self toggle ∪ space-mute ∪ permission-mute. Suppressed when the deafen state also flipped this tick (see Mute/deafen cue selection). |
+| `unmute.ogg` | "I am no longer muted" | self | `effectiveMuted` flips false while LK-connected. Suppressed when the deafen state also flipped this tick. |
+| `deafen.ogg` | "I am now deafened" | self | `effectiveDeafened` flips true while LK-connected. Takes priority over the coincident mute cue. |
+| `undeafen.ogg` | "I am no longer deafened" | self | `effectiveDeafened` flips false while LK-connected. Takes priority over the coincident unmute cue. |
+| `camera_on.ogg` | self camera enabled | self | `voiceStore.isCameraOn` flips true. |
+| `camera_off.ogg` | self camera disabled | self | `voiceStore.isCameraOn` flips false. |
+| `user_join.ogg` | someone (incl. self) joined the voice channel | everyone in call | self `isLiveKitConnected` flips true OR a remote participant appears in `participants[]`. |
+| `user_leave.ogg` | a remote participant left voice | everyone in call (excl. the leaver) | a userId disappears from `participants[]`. Suppressed for self (uses `disconnect.ogg`) and during teardown (`justDisconnected` guard). |
+| `disconnect.ogg` | self left voice | self | `isLiveKitConnected` flips false. |
+| `call_ringing.ogg` | incoming DM call (loop) | callee | `voiceStore.incomingCall !== null`. Loops while ringing; cleaned up on accept/reject/timeout. |
+| `call_calling.ogg` | outgoing DM call (loop) | caller | `voiceStore.outgoingCall !== null`. |
+| `stream_started.ogg` | any participant started a screen share | everyone in call (incl. the streamer) | a userId appears in the `participants[].isScreenSharing` set. |
+| `stream_ended.ogg` | any participant stopped a screen share | everyone in call | a userId leaves the `participants[].isScreenSharing` set. |
+| `stream_user_joined.ogg` | (a) a viewer started watching **my** stream; (b) **I** started watching someone's stream | streamer **and** the acting viewer | (a) streamer-side: `streamWatchers[selfUserId]` gains a watcher identity. (b) viewer-side: local feedback played by `handleViewerWatchToggle(_, true)` on the explicit "Watch Stream" action. |
+| `stream_user_left.ogg` | (a) a viewer stopped watching **my** stream; (b) **I** stopped watching someone's stream | streamer **and** the acting viewer | (a) streamer-side: `streamWatchers[selfUserId]` loses a watcher identity (suppressed for the whole set when self-stream-end fires — see Mechanism Notes). (b) viewer-side: local feedback played by `handleViewerWatchToggle(_, false)` on the explicit "Stop Watching" action. |
+| `message.ogg` | new chat message arrived | self | `shouldPlayMessageSound` returns true (DM channel OR content mentions any of the user's self-ids). User can flip `messageSoundAllChannels` to fire on every channel. |
 
 ---
 
@@ -59,6 +64,43 @@ ever entering the channel — the `effectiveMuted` flag flips true *after*
 connect because the keyed lookup resolves only once `currentVoiceChannelId` is
 set). Mid-call mod-mute remains audible.
 
+### Mute/deafen cue selection
+
+Deafening is not independent of muting: `voiceStore.toggleDeafen` flips
+`isMuted` together with `isDeafened` in a single atomic `set()` (deafen ⇒
+muted, undeafen ⇒ unmuted), mirroring Discord. SoundController samples both
+effective states on the same store tick, so firing a cue per changed flag would
+play `mute` **and** `deafen` at once when the user hits deafen.
+
+`selectVoiceStateSound(prev, next)` (`utils/voiceSoundTransitions.ts`) resolves
+this to a single cue: if the deafen state changed it returns `deafen`/`undeafen`
+and the coincident mute change is treated as a side effect and suppressed;
+otherwise a mute change returns `mute`/`unmute`. Pure helper, unit-tested.
+
+### Viewer-side watch feedback
+
+`stream_user_joined` / `stream_user_left` also play on the **viewer's own**
+machine as feedback for an explicit watch/stop action, via
+`handleViewerWatchToggle` in `StreamTile.tsx` — the same chokepoint that
+broadcasts the `stream_watch` ping. The cue is played directly (not derived
+from a `watchingStreams` diff) for two reasons: (1) automatic teardown paths
+(streamer stops sharing, participant disconnect) mutate `watchingStreams`
+without being the viewer's action and must stay silent on the viewer side —
+they already get `stream_ended`; (2) a direct local play is independent of the
+data-channel round-trip to the streamer, so the viewer gets identical feedback
+on every platform (Safari and the Electron desktop app alike). This is
+orthogonal to the streamer-side diff below, which fires on a *different*
+machine for that streamer's watcher set — the two never double on one client.
+
+### Playback envelope (anti-pop)
+
+`AudioManager.playSound` wraps every cue in a short gain envelope — a 10ms
+fade-in on start and (for non-looping cues) a 10ms fade-out before the buffer
+ends. Starting a buffer at a non-zero sample amplitude produces an audible
+click/pop; the envelope removes it. Most noticeable on the looping call cues
+(`call_calling` / `call_ringing`), which previously popped on every start.
+Mirrors the envelope already used by `playTestTone`.
+
 ### Viewer tracking — data-channel protocol
 
 LiveKit JS 2.17 does **not** expose per-subscriber events on the publisher
@@ -147,6 +189,6 @@ of them is a future change that requires sourcing new audio:
 - DM call accepted / connected (the moment ringing transitions to active)
 - DM call missed / declined / ended-remotely
 - Moderator move-to-channel / kick-from-voice (the LK disconnect already plays
-  `disconnect.mp3` for forced disconnects)
+  `disconnect.ogg` for forced disconnects)
 - Friend request received / accepted
 - Mention-everyone / @here (Backspace doesn't currently parse these)
diff --git a/packages/web/public/sounds/call_calling.mp3 b/packages/web/public/sounds/call_calling.mp3
deleted file mode 100644
index f0d7813c..00000000
Binary files a/packages/web/public/sounds/call_calling.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/call_calling.ogg b/packages/web/public/sounds/call_calling.ogg
new file mode 100644
index 00000000..726e4e4c
Binary files /dev/null and b/packages/web/public/sounds/call_calling.ogg differ
diff --git a/packages/web/public/sounds/call_ringing.mp3 b/packages/web/public/sounds/call_ringing.mp3
deleted file mode 100644
index fa4202b5..00000000
Binary files a/packages/web/public/sounds/call_ringing.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/call_ringing.ogg b/packages/web/public/sounds/call_ringing.ogg
new file mode 100644
index 00000000..01a5115f
Binary files /dev/null and b/packages/web/public/sounds/call_ringing.ogg differ
diff --git a/packages/web/public/sounds/camera_off.mp3 b/packages/web/public/sounds/camera_off.mp3
deleted file mode 100644
index 41537e86..00000000
Binary files a/packages/web/public/sounds/camera_off.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/camera_off.ogg b/packages/web/public/sounds/camera_off.ogg
new file mode 100644
index 00000000..6b7665b2
Binary files /dev/null and b/packages/web/public/sounds/camera_off.ogg differ
diff --git a/packages/web/public/sounds/camera_on.mp3 b/packages/web/public/sounds/camera_on.mp3
deleted file mode 100644
index d1a2db04..00000000
Binary files a/packages/web/public/sounds/camera_on.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/camera_on.ogg b/packages/web/public/sounds/camera_on.ogg
new file mode 100644
index 00000000..14c40645
Binary files /dev/null and b/packages/web/public/sounds/camera_on.ogg differ
diff --git a/packages/web/public/sounds/deafen.mp3 b/packages/web/public/sounds/deafen.mp3
deleted file mode 100644
index 705b4ecc..00000000
Binary files a/packages/web/public/sounds/deafen.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/deafen.ogg b/packages/web/public/sounds/deafen.ogg
new file mode 100644
index 00000000..a9ceebc7
Binary files /dev/null and b/packages/web/public/sounds/deafen.ogg differ
diff --git a/packages/web/public/sounds/disconnect.mp3 b/packages/web/public/sounds/disconnect.mp3
deleted file mode 100644
index 07ff77e2..00000000
Binary files a/packages/web/public/sounds/disconnect.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/disconnect.ogg b/packages/web/public/sounds/disconnect.ogg
new file mode 100644
index 00000000..80a9b9da
Binary files /dev/null and b/packages/web/public/sounds/disconnect.ogg differ
diff --git a/packages/web/public/sounds/message.mp3 b/packages/web/public/sounds/message.mp3
deleted file mode 100644
index 71724cd4..00000000
Binary files a/packages/web/public/sounds/message.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/message.ogg b/packages/web/public/sounds/message.ogg
new file mode 100644
index 00000000..5a7b0ff2
Binary files /dev/null and b/packages/web/public/sounds/message.ogg differ
diff --git a/packages/web/public/sounds/mute.mp3 b/packages/web/public/sounds/mute.mp3
deleted file mode 100644
index 70124ec2..00000000
Binary files a/packages/web/public/sounds/mute.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/mute.ogg b/packages/web/public/sounds/mute.ogg
new file mode 100644
index 00000000..ce25d90f
Binary files /dev/null and b/packages/web/public/sounds/mute.ogg differ
diff --git a/packages/web/public/sounds/stream_ended.mp3 b/packages/web/public/sounds/stream_ended.mp3
deleted file mode 100644
index d6e00589..00000000
Binary files a/packages/web/public/sounds/stream_ended.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/stream_ended.ogg b/packages/web/public/sounds/stream_ended.ogg
new file mode 100644
index 00000000..e2cdcd83
Binary files /dev/null and b/packages/web/public/sounds/stream_ended.ogg differ
diff --git a/packages/web/public/sounds/stream_started.mp3 b/packages/web/public/sounds/stream_started.mp3
deleted file mode 100644
index 3c7aaee9..00000000
Binary files a/packages/web/public/sounds/stream_started.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/stream_started.ogg b/packages/web/public/sounds/stream_started.ogg
new file mode 100644
index 00000000..55530cc4
Binary files /dev/null and b/packages/web/public/sounds/stream_started.ogg differ
diff --git a/packages/web/public/sounds/stream_user_joined.mp3 b/packages/web/public/sounds/stream_user_joined.mp3
deleted file mode 100644
index 1d13728d..00000000
Binary files a/packages/web/public/sounds/stream_user_joined.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/stream_user_joined.ogg b/packages/web/public/sounds/stream_user_joined.ogg
new file mode 100644
index 00000000..b6806e8e
Binary files /dev/null and b/packages/web/public/sounds/stream_user_joined.ogg differ
diff --git a/packages/web/public/sounds/stream_user_left.mp3 b/packages/web/public/sounds/stream_user_left.mp3
deleted file mode 100644
index 5c733e60..00000000
Binary files a/packages/web/public/sounds/stream_user_left.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/stream_user_left.ogg b/packages/web/public/sounds/stream_user_left.ogg
new file mode 100644
index 00000000..b333375f
Binary files /dev/null and b/packages/web/public/sounds/stream_user_left.ogg differ
diff --git a/packages/web/public/sounds/undeafen.mp3 b/packages/web/public/sounds/undeafen.mp3
deleted file mode 100644
index 390d6c2f..00000000
Binary files a/packages/web/public/sounds/undeafen.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/undeafen.ogg b/packages/web/public/sounds/undeafen.ogg
new file mode 100644
index 00000000..21d5da96
Binary files /dev/null and b/packages/web/public/sounds/undeafen.ogg differ
diff --git a/packages/web/public/sounds/unmute.mp3 b/packages/web/public/sounds/unmute.mp3
deleted file mode 100644
index c45905fb..00000000
Binary files a/packages/web/public/sounds/unmute.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/unmute.ogg b/packages/web/public/sounds/unmute.ogg
new file mode 100644
index 00000000..5f929273
Binary files /dev/null and b/packages/web/public/sounds/unmute.ogg differ
diff --git a/packages/web/public/sounds/user_join.mp3 b/packages/web/public/sounds/user_join.mp3
deleted file mode 100644
index 2ab7491d..00000000
Binary files a/packages/web/public/sounds/user_join.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/user_join.ogg b/packages/web/public/sounds/user_join.ogg
new file mode 100644
index 00000000..9bd924dd
Binary files /dev/null and b/packages/web/public/sounds/user_join.ogg differ
diff --git a/packages/web/public/sounds/user_leave.mp3 b/packages/web/public/sounds/user_leave.mp3
deleted file mode 100644
index 4169a259..00000000
Binary files a/packages/web/public/sounds/user_leave.mp3 and /dev/null differ
diff --git a/packages/web/public/sounds/user_leave.ogg b/packages/web/public/sounds/user_leave.ogg
new file mode 100644
index 00000000..8305e422
Binary files /dev/null and b/packages/web/public/sounds/user_leave.ogg differ
diff --git a/packages/web/src/audio/AudioManager.ts b/packages/web/src/audio/AudioManager.ts
index 5578d284..0b18ff6b 100644
--- a/packages/web/src/audio/AudioManager.ts
+++ b/packages/web/src/audio/AudioManager.ts
@@ -169,7 +169,7 @@ export class AudioManager {
     if (!this.ctx) this.initContext();
     
     try {
-      const response = await fetch(`/sounds/${name}.mp3`);
+      const response = await fetch(`/sounds/${name}.ogg`);
       if (!response.ok) throw new Error(`Failed to load sound: ${name}`);
       const arrayBuffer = await response.arrayBuffer();
       const audioBuffer = await this.ctx!.decodeAudioData(arrayBuffer);
@@ -191,12 +191,34 @@ export class AudioManager {
     source.loop = options.loop || false;
 
     const gainNode = this.ctx.createGain();
-    gainNode.gain.value = options.volume ?? 0.8;
+    const targetVolume = options.volume ?? 0.8;
+
+    // Short attack/release envelope to avoid the click/pop that occurs when a
+    // buffer starts (or ends) at a non-zero sample amplitude. Without this the
+    // waveform's first sample jumps from silence instantly, producing an
+    // audible pop — most noticeable on the looping call cues. Mirrors the
+    // envelope used by playTestTone().
+    const now = this.ctx.currentTime;
+    const attack = 0.01; // 10ms fade-in — kills the start pop, imperceptible
+    gainNode.gain.setValueAtTime(0, now);
+    gainNode.gain.linearRampToValueAtTime(targetVolume, now + attack);
+
+    // Tail fade-out for one-shots so they don't pop at the natural end of the
+    // buffer. Looping cues are stopped explicitly by the caller, so they ramp
+    // in once and hold; no tail ramp is scheduled for them.
+    if (!source.loop) {
+      const release = 0.01; // 10ms fade-out
+      const dur = buffer.duration;
+      if (dur > attack + release) {
+        gainNode.gain.setValueAtTime(targetVolume, now + dur - release);
+        gainNode.gain.linearRampToValueAtTime(0, now + dur);
+      }
+    }
 
     source.connect(gainNode);
     gainNode.connect(this.masterBoost!);
 
-    source.start(0);
+    source.start(now);
     return source;
   }
 
diff --git a/packages/web/src/components/voice/SoundController.tsx b/packages/web/src/components/voice/SoundController.tsx
index c69cff60..4c7ba806 100644
--- a/packages/web/src/components/voice/SoundController.tsx
+++ b/packages/web/src/components/voice/SoundController.tsx
@@ -5,11 +5,8 @@ import { useAuthStore } from '../../stores/authStore';
 import { useSpaceStore, isDmChannel, getChannelOrigin, getMyUserIdForOrigin } from '../../stores/spaceStore';
 import { AudioManager } from '../../audio/AudioManager';
 import { shouldPlayMessageSound } from '../../utils/notificationFilters';
-
-/** Compute the effective sound effect gain: base volume (0.8) scaled by the user's SFX slider (0–200). */
-function getSfxVolume(): number {
-  return 0.8 * (useVoiceStore.getState().soundEffectVolume / 100);
-}
+import { selectVoiceStateSound } from '../../utils/voiceSoundTransitions';
+import { getSfxVolume } from '../../utils/sfx';
 
 /**
  * Replicates the `useLiveKit` effective-mute formula on demand. Returns whether
@@ -84,12 +81,14 @@ export function SoundController() {
       // current effective state without firing.
       const eff = computeEffectiveSelfState(state);
       if (state.isLiveKitConnected && prev.current.isLiveKitConnected) {
-        if (eff.muted !== prev.current.effectiveMuted) {
-          audioManager.playSound(eff.muted ? 'mute' : 'unmute', sfxOpts);
-        }
-        if (eff.deafened !== prev.current.effectiveDeafened) {
-          audioManager.playSound(eff.deafened ? 'deafen' : 'undeafen', sfxOpts);
-        }
+        // Deafen toggles mute as an atomic side effect (see
+        // selectVoiceStateSound) — pick the single correct cue so deafening
+        // doesn't play the mute sound on top of the deafen sound.
+        const sound = selectVoiceStateSound(
+          { muted: prev.current.effectiveMuted, deafened: prev.current.effectiveDeafened },
+          { muted: eff.muted, deafened: eff.deafened },
+        );
+        if (sound) audioManager.playSound(sound, sfxOpts);
       }
       prev.current.effectiveMuted = eff.muted;
       prev.current.effectiveDeafened = eff.deafened;
diff --git a/packages/web/src/components/voice/StreamTile.tsx b/packages/web/src/components/voice/StreamTile.tsx
index fc866938..d5b8b359 100644
--- a/packages/web/src/components/voice/StreamTile.tsx
+++ b/packages/web/src/components/voice/StreamTile.tsx
@@ -5,6 +5,8 @@ import { useContextMenuStore, type ContextMenuItem } from '../../stores/contextM
 import { getActiveRoom, setStreamSubscription } from '../../hooks/useLiveKit';
 import { stopScreenShare, changeScreenShare } from '../../utils/screenShare';
 import { encodeStreamWatch } from '../../utils/streamWatchProtocol';
+import { AudioManager } from '../../audio/AudioManager';
+import { getSfxVolume } from '../../utils/sfx';
 import { ScreenShareSettingsPopover } from './ScreenShareSettingsPopover';
 import { useVoiceParticipantMeta } from '../../hooks/useVoiceParticipantMeta';
 import type { StreamTile as StreamTileType } from '../../hooks/useLiveKit';
@@ -141,7 +143,26 @@ function StreamAttenuationItem() {
   );
 }
 
-function broadcastStreamWatch(streamerUserId: string, watching: boolean): void {
+/**
+ * Handles a deliberate viewer watch / stop-watch action: plays the local
+ * feedback cue on the viewer's OWN machine and notifies the streamer so their
+ * streamer-side watcher set updates.
+ *
+ * Called only from explicit user-action sites (the "Watch Stream" button and
+ * the watch/stop context-menu items) — never from automatic teardown paths
+ * (streamer stops sharing, participant disconnect), which must stay silent on
+ * the viewer side. The local cue is played directly rather than derived from a
+ * `watchingStreams` diff precisely so those teardown paths don't trigger it.
+ *
+ * The cue plays unconditionally (independent of the data-channel round-trip to
+ * the streamer), so the viewer gets identical feedback on every platform —
+ * Safari and the Electron desktop app alike.
+ */
+function handleViewerWatchToggle(streamerUserId: string, watching: boolean): void {
+  AudioManager.getInstance().playSound(
+    watching ? 'stream_user_joined' : 'stream_user_left',
+    { volume: getSfxVolume() },
+  );
   const room = getActiveRoom();
   if (!room) return;
   const payload = encodeStreamWatch({ type: 'stream_watch', target: streamerUserId, watching });
@@ -275,7 +296,7 @@ export function StreamTile({ tile, large }: StreamTileProps) {
             onClick: () => {
               useVoiceStore.getState().unwatchStream(userId);
               setStreamSubscription(getActiveRoom(), identity, false);
-              broadcastStreamWatch(userId, false);
+              handleViewerWatchToggle(userId, false);
             },
           });
         } else {
@@ -289,7 +310,7 @@ export function StreamTile({ tile, large }: StreamTileProps) {
             onClick: () => {
               useVoiceStore.getState().watchStream(userId);
               setStreamSubscription(getActiveRoom(), identity, true);
-              broadcastStreamWatch(userId, true);
+              handleViewerWatchToggle(userId, true);
             },
           });
         }
@@ -333,7 +354,7 @@ export function StreamTile({ tile, large }: StreamTileProps) {
   const handleWatch = useCallback(() => {
     useVoiceStore.getState().watchStream(userId);
     setStreamSubscription(getActiveRoom(), participant.identity, true);
-    broadcastStreamWatch(userId, true);
+    handleViewerWatchToggle(userId, true);
   }, [userId, participant.identity]);
 
   const hasVideo = liveScreenTrack !== null;
diff --git a/packages/web/src/utils/notificationFilters.ts b/packages/web/src/utils/notificationFilters.ts
index 073d61f8..7fd22697 100644
--- a/packages/web/src/utils/notificationFilters.ts
+++ b/packages/web/src/utils/notificationFilters.ts
@@ -1,6 +1,6 @@
 /**
  * Decides whether a freshly-arrived chat message should fire the in-app
- * `message.mp3` cue. Pure, federation-aware (matches against any of the
+ * `message.ogg` cue. Pure, federation-aware (matches against any of the
  * caller's known self-ids).
  *
  * Rule (Discord-default):
diff --git a/packages/web/src/utils/sfx.ts b/packages/web/src/utils/sfx.ts
new file mode 100644
index 00000000..7e16b93e
--- /dev/null
+++ b/packages/web/src/utils/sfx.ts
@@ -0,0 +1,13 @@
+import { useVoiceStore } from '../stores/voiceStore';
+
+/** Base gain applied to every sound effect before the user's SFX slider. */
+export const SFX_BASE_VOLUME = 0.8;
+
+/**
+ * Effective sound-effect gain: the base SFX volume scaled by the user's SFX
+ * slider (0–200, where 100 = unity). Read at play time so volume changes take
+ * effect on the next cue without re-subscribing.
+ */
+export function getSfxVolume(): number {
+  return SFX_BASE_VOLUME * (useVoiceStore.getState().soundEffectVolume / 100);
+}
diff --git a/packages/web/src/utils/voiceSoundTransitions.test.ts b/packages/web/src/utils/voiceSoundTransitions.test.ts
new file mode 100644
index 00000000..efd416de
--- /dev/null
+++ b/packages/web/src/utils/voiceSoundTransitions.test.ts
@@ -0,0 +1,57 @@
+import { describe, it, expect } from 'vitest';
+import { selectVoiceStateSound } from './voiceSoundTransitions';
+
+describe('selectVoiceStateSound', () => {
+  it('returns null when nothing changed', () => {
+    expect(
+      selectVoiceStateSound({ muted: false, deafened: false }, { muted: false, deafened: false }),
+    ).toBeNull();
+    expect(
+      selectVoiceStateSound({ muted: true, deafened: false }, { muted: true, deafened: false }),
+    ).toBeNull();
+  });
+
+  it('plays mute when only mute flips on', () => {
+    expect(
+      selectVoiceStateSound({ muted: false, deafened: false }, { muted: true, deafened: false }),
+    ).toBe('mute');
+  });
+
+  it('plays unmute when only mute flips off', () => {
+    expect(
+      selectVoiceStateSound({ muted: true, deafened: false }, { muted: false, deafened: false }),
+    ).toBe('unmute');
+  });
+
+  it('plays only deafen (not mute) when deafening also forces mute on', () => {
+    // toggleDeafen sets { isMuted: true, isDeafened: true } atomically.
+    expect(
+      selectVoiceStateSound({ muted: false, deafened: false }, { muted: true, deafened: true }),
+    ).toBe('deafen');
+  });
+
+  it('plays only undeafen (not unmute) when undeafening also clears mute', () => {
+    // toggleDeafen sets { isMuted: false, isDeafened: false } atomically.
+    expect(
+      selectVoiceStateSound({ muted: true, deafened: true }, { muted: false, deafened: false }),
+    ).toBe('undeafen');
+  });
+
+  it('plays deafen when deafening while already muted (mute unchanged)', () => {
+    expect(
+      selectVoiceStateSound({ muted: true, deafened: false }, { muted: true, deafened: true }),
+    ).toBe('deafen');
+  });
+
+  it('plays undeafen when un-deafened but still muted (e.g. moderator space-mute persists)', () => {
+    expect(
+      selectVoiceStateSound({ muted: true, deafened: true }, { muted: true, deafened: false }),
+    ).toBe('undeafen');
+  });
+
+  it('prioritizes the deafen cue when both states change in one tick', () => {
+    expect(
+      selectVoiceStateSound({ muted: false, deafened: true }, { muted: true, deafened: false }),
+    ).toBe('undeafen');
+  });
+});
diff --git a/packages/web/src/utils/voiceSoundTransitions.ts b/packages/web/src/utils/voiceSoundTransitions.ts
new file mode 100644
index 00000000..6325dbd2
--- /dev/null
+++ b/packages/web/src/utils/voiceSoundTransitions.ts
@@ -0,0 +1,34 @@
+/**
+ * Pure decision logic for the self mute/deafen audio cues.
+ *
+ * Deafening is not an independent state: `voiceStore.toggleDeafen` flips
+ * `isMuted` together with `isDeafened` in a single atomic update (deafen ⇒
+ * muted, undeafen ⇒ unmuted), mirroring Discord. The SoundController samples
+ * both effective states on the same store tick, so a naive "fire on each
+ * change" approach plays the mute *and* deafen cue at once when the user hits
+ * deafen.
+ *
+ * The coincident mute change is a side effect of the deafen action, not a
+ * distinct user intent, so it must be suppressed: when the deafen state
+ * changed, only the deafen/undeafen cue plays. Pure mute toggles (deafen
+ * unchanged) still play the mute/unmute cue.
+ */
+export interface VoiceMuteState {
+  muted: boolean;
+  deafened: boolean;
+}
+
+export type VoiceStateSound = 'mute' | 'unmute' | 'deafen' | 'undeafen' | null;
+
+export function selectVoiceStateSound(
+  prev: VoiceMuteState,
+  next: VoiceMuteState,
+): VoiceStateSound {
+  const deafenedChanged = prev.deafened !== next.deafened;
+  if (deafenedChanged) return next.deafened ? 'deafen' : 'undeafen';
+
+  const mutedChanged = prev.muted !== next.muted;
+  if (mutedChanged) return next.muted ? 'mute' : 'unmute';
+
+  return null;
+}