How to convert NIST to RIFF wav file
OK, I solve the problem. The problem was that I was overriding the files when I used the "sox" command, as I want them to convert into RIFF format. However, "sox" didn't convert them correctly when using the same file name, i.e. when overriding the files. When I changed the file name of the overridden files, it converted them into RIFF format.