There have been several inquiries lately about Tsunami CV47 and the Playable Whistle function of the DT400 and DT402 throttle. Digitrax does not use CV47 for any of its decoders and therefore this CV is not mentioned in our documentation.
After doing some research we found that CV47 must be programmed to a value of 127 to enable the Playable Whistle on Soundtraxx Tsunami decoders.