Use laptop MP3 TTS playback

README.md

@@ -109,7 +109,39 @@ npm run start
 
 ## Speech Input And Playback
 
-Playback works directly in Expo Go. AI replies are read aloud through the iPhone speaker. The chat also has buttons for `Read last answer` and `Stop`.
+Playback uses a local MP3 TTS server on the laptop. AI replies are sent to the laptop, converted to an MP3 with a Microsoft neural English voice, and then played on the iPhone. This avoids the robotic iPhone system voice.
+
+Start the TTS server in a second terminal:
+
+```bash
+npm run tts:start
+```
+
+For Expo Go on iPhone, `.env` must point to the laptop IP:
+
+```text
+EXPO_PUBLIC_TTS_BASE_URL=http://192.168.10.33:3333
+EXPO_PUBLIC_TTS_VOICE=en-US-JennyNeural
+EXPO_PUBLIC_TTS_RATE=0.88
+EXPO_PUBLIC_TTS_PITCH=+0Hz
+```
+
+Useful English voices:
+
+- `en-US-JennyNeural`
+- `en-US-AvaNeural`
+- `en-US-EmmaNeural`
+- `en-US-GuyNeural`
+- `en-GB-SoniaNeural`
+- `en-GB-RyanNeural`
+
+You can list available voices while the TTS server is running:
+
+```text
+http://192.168.10.33:3333/voices
+```
+
+The chat has buttons for `Read last answer` and `Stop`.
 
 Speech input currently works through the iPhone keyboard: