These samples are headerless DSP's. You need a few things before you can convert them.
First, download the latest vgmstream:https://github.com/losnoco/vgmstream/releases
Upon extraction you should see an executable called "test.exe".
Next, download this zip file:
zenpinball_pdsp.zip [281 Bytes]
Downloaded 12 times
Extract that zip archive and make sure the file is still named .pdsp.txth
if it is named pdsp.txth
without the dot in front of "pdsp", it will not work.
Now that you've downloaded vgmstream and the TXTH, drag and drop the TXTH into the same folder as "test.exe" (executable in vgmstream folder). Then, drag all your samples into the same folder as "test.exe". When you drag and drop the *.pdsp files onto test, it should work now. Happy converting! Batch implementation to speed things up.
*Navigate to folder in command prompt*
for %f in ("*.pdsp") do test "%f"