I see Bachmann has added to the Product Reference (http://www.bachmanntrains.com/home-usa/references.php)section of the Bachmann Trains website a link for
SPECTRUM STEAM SOUND USER'S GUIDE (Tsunami Sound Decoder)
The link includes Spectrum Technical Reference.
I have not taken time to compare these documentations to any DCC SOUND ON BOARD Spectrum steam locomotive equipped with SoundTraxx Tsunami Digital Sound Technology decoder.