OK, I think I found where these settings are.
[[OEPocketsphinxController sharedInstance] setVadThreshold:0.5];
[[OEPocketsphinxController sharedInstance] setLatencyTuning: 1];
And this is what I see at the header file.
/**Speech/Silence threshhold setting. You may not need to make any changes to this, however, if you are experiencing quiet background noises triggering speech recognition, you can raise this to a value from 2-5 to 3.5 for the English acoustic model, and between 3.0 and 4.5 for the Spanish acoustic model. If you are experiencing too many words being ignored you can reduce this. The maximum value is 5.0 and the minimum is .5. For the English model, values less than 1.5 or more than 3.5 are likely to lead to poor results. For the Spanish model, higher values can be used. Please test any changes here carefully to see what effect they have on your user experience.*/
@property (nonatomic, assign) float vadThreshold;
I guess I will try to set it to 3.5?