CVU file is a CVSD Unfiltered Audio. Continuously Variable Slope Delta modulation (unfiltered) is an alternative handler for CVSD that is unfiltered but can be used with any bit-rate.
SND is a file extension for a sound file used with a variety of platforms. SND stands for SouND. SND files may contain audio data specific to a Macintosh sound resource (from Mac OS Classic), an AKAI MPC audio sample, a generic Amiga sound, or other audio file. SND files can often be opened by Apple’s Quicktime Player