Thanks so much for the reply. CV 113 is set to "0" (which I believe disables the timeout). The sound doesn't shutdown when the loco comes to a stop (as one might expect from quiet mode). It happens when you hit the direction button.
I'd just point out the type of engine it was installed in doesn't really matter; titling your post something like "Soundtraxx Tsunami - sound shuts down on change of direction" might generate more responses.
Anyway, maybe make sure CV113 is set to zero. That is the "Quiet Mode" control; it determines how long the engine sits at speed step zero before the sound shuts down. The higher the number (1-255), the longer it waits. Making it zero shuts off quiet mode so the engine sound continues without stopping.
Has anyone ever had a loco where the sound shuts down whenever you change direction? I believe the sound is an older SoundTraxx series R Tsunami.