TTS voice will work only with proper .apk .
Try to add in sys.txt :
[sound]
queue_length=200
Also, you can play with :
[android]
navigation_audio_stream=4
; 0-STREAM_VOICE_CALL, 1-STREAM_SYSTEM, 2-STREAM_RING, 3-STREAM_MUSIC, 4-STREAM_ALARM, 5-STREAM_NOTIFICATION