CMUSphinx German command & control app, bad accuracy

I'm trying to implement a German command and control application with CMUSphinx and Java. So far, the application should recognize only a few words (numbers from 1 to 9, yes/no).

Unfortunately the accuracy is very bad. It seems, if a word is recognized correctly, it is only by chance.

Here is my java code so far (adapted from the tutorial):

public static void main(String[] args) throws IOException {

    // Configuration Object
    Configuration configuration = new Configuration();

    // Set path to the acoustic model.
    configuration.setAcousticModelPath("resource:/cmusphinx-de-voxforge-5.2");

    // Set path to the dictionary.
    configuration.setDictionaryPath("resource:/cmusphinx-voxforge-de.dic");

    // use grammar
    configuration.setGrammarPath("resource:/");
    configuration.setGrammarName("dialog");
    configuration.setUseGrammar(true);

    LiveSpeechRecognizer recognizer = new LiveSpeechRecognizer(configuration);

    recognizer.startRecognition(true);
    SpeechResult result;
    while ((result = recognizer.getResult()) != null) {
        System.out.format("Hypothesis: %s\n", result.getHypothesis());
    }
    recognizer.stopRecognition();
}

Here is my grammer file:

#JSGF V1.0;

grammar dialog;

public <digit> = 1 | 2 | 3 | 4 |5 | 6 | 7 | 8 | 9 | ja | nein; 

I've downloaded the German acoustic model and dictionary from here: https://sourceforge.net/projects/cmusphinx/files/Acoustic%20and%20Language%20Models/German/

Is there something obvious I'm missing here? Where is the problem?

Thanks in advance and kind regards.

I have tried to use pocketsphinx with Eng and German model and accuracy is good when it comes with predefined/limited set of phrases! You can forget about general things like "could you please find me a restaurant in the downtown".

To achieve good accuracy with a pocketshinx:

• Check that your mic, audio device, file and everything are 16 kHz while general model is trained with such acoustic examples.
• You should create your own limited dictionary you cannot use cmusphinx-voxforge-de.dic while accuracy is dramatically dropped.
• You should create your own language model.
• You can try to modify pronunciation files to fit your accent.

You can search for Jasper project on GitLab to see how it's implemented. Also you can check the documentation