use default audio devices

app.py

@@ -83,8 +83,9 @@ async def main():
         microphone_input,
         speaker_output,
     ) = create_streaming_microphone_input_and_speaker_output(
-        use_default_devices=False,
+        use_default_devices=True,
         logger=logger,
+        use_blocking_speaker_output=True,
     )
 
     conversation = StreamingConversation(