Currently the transcription toolbar function PlayAtSpeed has a maximum value of 3X. My editing deck allows much higher multiples, I am used to searching raw data for “non-music” (speech etc.) and can recognize the difference at speeds between 7X and 10X.
If we look at the source code, AudacitySVNsrcwidgetsASlider.cpp, at or near line number 399:
case SPEED_SLIDER: minValue = 0.01f; //maxValue = 3.0f; maxValue = 20.0f; stepValue = STEP_CONTINUOUS; break;
We see that changing maxValue from 3 to 20 seems to do the trick. I tested this and it seems to work just fine although speeds above 10X appear to be useless for my purposes.