int bufsize = AudioTrack.getMinBufferSize(16000,
AudioFormat.CHANNEL_OUT_STEREO,
AudioFormat.ENCODING_PCM_16BIT);

AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_VOICE_CALL,
                                                    16000,
                          AudioFormat.CHANNEL_OUT_STEREO,
                          AudioFormat.ENCODING_PCM_16BIT,
                          bufsize,
                          AudioTrack.MODE_STREAM);
audioTrack.play();

audioTrack.write(byte[], int, int);