havn't sound on android

On Android there are several volume sttings. You either can go to the phone settings and change the volume for playing audio, or (easier)
Press the play audio button on our application and at the same time toggle the audio volume switch on the device.

I had the same issue. For some reason, sound volume in the trainchinese app adjust ringer volume, not media volume (htc sensation). If you go into another app or into settings, turn up media volume and go back into the app. This should resolve your problem.