A 32-bit version does not exist as far as I know.
It might be useful for older interfaces with 32-bit-drivers only, but these interfaces might be too slow for soundjack anyway.
On Macs the 32-bit-only machines won’t be able to run the MacOS X needed for soundjack, so this is not an issue there.
On Windows, the machines that cannot run a 64-bit-version might be too slow anyway (no multiple processors).
It is an issue on my Mac that runs a 32-bit version of Windows 10 in BOOTCAMP because of some other driver that I need there which is not available in 64-bit. But this is a rather special case. And soundjack runs better under MacOS X anyway. So not a real issue for me.
But best contact Alex directly if he could make a 32-bit Windows version available or not.