I worked out that command line years ago, and I don't even remember what it all does. And all of my machines are linux, so I can't test out what it is for OS X

I worked out that command line years ago, and I don't even remember what it all does. And all of my machines are linux, so I can't test out what it is for OS X. But from looking at the soxformat man page, I'm guessing you might try replacing "alsa pulse" with "coreaudio". You can also look at the output of "sox -h" to see what audio device drivers your sox has.