diff --git a/backend/main.py b/backend/main.py
index 4ea607e..53dd9f6 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -414,6 +414,10 @@ async def preview_voice(request: VoicePreviewRequest):
         else:
             raise ValueError(f"Unknown engine: {tts_service.engine_name}")
         
+        # Check if audio was generated
+        if audio is None or len(audio) == 0:
+            raise ValueError("No audio generated - voice model may be missing")
+        
         # Convert to WAV bytes
         buffer = io.BytesIO()
         sf.write(buffer, audio, sample_rate, format='WAV')
@@ -427,7 +431,31 @@ async def preview_voice(request: VoicePreviewRequest):
             media_type="audio/wav",
             headers={"Content-Disposition": "inline; filename=preview.wav"}
         )
-        
+    
+    except FileNotFoundError as e:
+        logger.error(f"Voice model not found: {str(e)}")
+        return JSONResponse(
+            status_code=status.HTTP_404_NOT_FOUND,
+            content={
+                "error": "VoiceModelNotFound",
+                "message": f"Voice model '{request.voice}' not found. Please download Piper voice models manually.",
+                "details": {
+                    "voice": request.voice,
+                    "engine": tts_service.engine_name,
+                    "setup_guide": "See backend/PIPER_SETUP.md for instructions"
+                }
+            }
+        )
+    except ValueError as e:
+        logger.error(f"Validation error during preview: {str(e)}")
+        return JSONResponse(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            content={
+                "error": "ValidationError",
+                "message": str(e),
+                "details": {"voice": request.voice, "engine": tts_service.engine_name}
+            }
+        )
     except Exception as e:
         logger.error(f"Error during voice preview: {str(e)}", exc_info=True)
         return JSONResponse(
diff --git a/backend/piper_models/en_US-lessac-medium.onnx.json b/backend/piper_models/en_US-lessac-medium.onnx.json
new file mode 100644
index 0000000..a05a475
--- /dev/null
+++ b/backend/piper_models/en_US-lessac-medium.onnx.json
@@ -0,0 +1 @@
+Entry not found
\ No newline at end of file
diff --git a/frontend/src/components/VoiceAssignmentSection.tsx b/frontend/src/components/VoiceAssignmentSection.tsx
index a19d352..d60518e 100644
--- a/frontend/src/components/VoiceAssignmentSection.tsx
+++ b/frontend/src/components/VoiceAssignmentSection.tsx
@@ -262,6 +262,11 @@ export default function VoiceAssignmentSection({
     } catch (error) {
       console.error('Preview failed:', error);
       setPreviewingRole(null);
+      
+      // Show user-friendly error message
+      if (error instanceof Error) {
+        alert(`Voice preview failed: ${error.message}\n\nIf using Piper TTS, make sure voice models are downloaded. See backend/PIPER_SETUP.md for instructions.`);
+      }
     }
   };
 
@@ -350,10 +355,19 @@ export default function VoiceAssignmentSection({
             </button>
           </div>
           {currentEngine === 'piper' && (
-            <div className="mt-3 p-3 bg-blue-50 border border-blue-200 rounded-lg">
-              <p className="text-sm text-blue-900">
-                <strong>✨ Pitch Control:</strong> Piper allows you to adjust voice pitch per character (coming soon in UI)
-              </p>
+            <div className="mt-3 space-y-2">
+              <div className="p-3 bg-blue-50 border border-blue-200 rounded-lg">
+                <p className="text-sm text-blue-900">
+                  <strong>✨ Pitch Control:</strong> Piper allows you to adjust voice pitch per character (coming soon in UI)
+                </p>
+              </div>
+              <div className="p-3 bg-yellow-50 border border-yellow-300 rounded-lg">
+                <p className="text-sm text-yellow-900">
+                  <strong>⚠️ Setup Required:</strong> Piper voice models must be downloaded manually. 
+                  See <code className="bg-yellow-100 px-1 rounded">backend/PIPER_SETUP.md</code> for instructions.
+                  If voices don't work, you may need to download the model files first.
+                </p>
+              </div>
             </div>
           )}
         </div>