diff --git a/client/assets/audio/sfx_npc_murmur.ogg b/client/assets/audio/sfx_npc_murmur.ogg
new file mode 100644
index 000000000..b401d7350
Binary files /dev/null and b/client/assets/audio/sfx_npc_murmur.ogg differ
diff --git a/docs/assets/audio/sfx.md b/docs/assets/audio/sfx.md
index 58903680e..a9b5116dd 100644
--- a/docs/assets/audio/sfx.md
+++ b/docs/assets/audio/sfx.md
@@ -15,6 +15,7 @@ Mixed methods depending on duration and character:
 |----|----------|--------|-----|--------|----------|-------------|--------|
 | SFX-001 | `sfx_footstep_metal_walk.ogg` | done | Player Actions | SAO hybrid | 0.3s | Single footstep on metal grating. Walk pace. SAO 5s/100 steps/CFG 8, best transient trimmed at 2.42s, LUFS -16 normalized. | S10 #327 |
 | SFX-002 | `sfx_footstep_metal_run.ogg` | done | Player Actions | SAO hybrid | 0.3s | Faster footstep, sprint pace. Louder — player is broadcasting position (D-053 acoustic footprint). SAO 5s/100 steps/CFG 8, best transient trimmed at 1.03s, LUFS -16 normalized. | S10 #327 |
+| SFX-003 | `sfx_npc_murmur.ogg` | done | World SFX | SAO | 5s | NPC proximity conversation murmur. Human voices in adjacent room, direction and cadence distinguishable, words not. Organic family. SAO 5s/100 steps/CFG 8, LUFS -16 normalized. Selected from 3 candidates (richest texture). | S13 #532 |
 
 ## Detailed Entries
 
@@ -25,6 +26,17 @@ Mixed methods depending on duration and character:
 - **Integration:** Triggered by player movement tick. Positional (AudioStreamPlayer2D at player position) — maps to camera-relative stereo per D-018.
 - **Cross-reference:** D-038 (#5), D-053 (movement stances as acoustic decisions)
 
+### SFX-003: sfx_npc_murmur
+- **Sonic family:** organic (physical world — human warmth, natural decay)
+- **Bus rationale:** World SFX — this is information about other people in the world, not player feedback. Positional (AudioStreamPlayer2D at NPC cluster position).
+- **Design intent (D-072):** Universal asset — single murmur plays at all NPC proximity events. Zone ambient determines conspicuousness naturally: bar's dense ambient buries it, corridor's sparse ambient exposes it. No zone-specific variants needed.
+- **Aesthetic (D-074):** Organic family. Warm, lived-in, no lattice processing. Mid-freq 200-800Hz texture per station palette "functional warmth" (D-074 conversation murmur band).
+- **Propagation (D-018):** Close range: intelligible as "voices, nearby." Medium range: muffled. Long range: lost in ambient floor.
+- **Eavesdrop interaction (D-071):** Player ListeningFocus boost increases effective reception range. Same asset, confidence varies with proximity and skill.
+- **Generation:** SAO 5s / 100 steps / CFG 8. Prompt: "Warm organic audio, natural sound recording, slight room ambience, lived-in industrial space, realistic acoustic properties, authentic environmental sound. Single isolated sound effect, clean recording, 5 seconds duration, clear attack and natural decay, no background noise, no reverb tail beyond natural. Human voices murmuring through a thin wall or partition, two or three people in low conversation in the adjacent room, words muffled and indistinct, direction and gentle cadence audible, warm mid-frequency vocal texture 200-800Hz, soft intimate conversation murmur, no music, no intelligible words." 3 candidates generated (5s/CFG8, 6s/CFG7, 4s/CFG9). Candidate 1 selected (richest OGG texture, clearest spatial framing). Post-processed: trim, LUFS -16, OGG.
+- **Integration:** Event-driven — fires when player enters NPC cluster proximity range. Not looped continuously; retriggered on proximity events. Loop-capable (5s has natural loop structure) if client opts to sustain during eavesdrop.
+- **Cross-reference:** D-072 (universal murmur decision), D-071 (ListeningFocus eavesdrop), D-074 (organic aesthetic), D-018 (sound propagation model)
+
 ## Future Expansion
 
 SFX will grow significantly with:
@@ -32,7 +44,6 @@ SFX will grow significantly with:
 - Door open/close, machinery activation → World SFX bus
 - Combat impacts, weapon sounds → Player Actions bus
 - Environmental events per planet/biome
-- NPC conversation murmur (event-driven, point-source) → World SFX bus
 
 When this file exceeds ~50 entries, split by domain:
 - `sfx-movement.md` (footsteps, stance variants)