Alert sounds: Nuvi 1690 - wav - mp3

After doing a lot of research, I was unable to find definitive info on the required sound file format for POILoader and the Garmin 1690. In the dearth of info, I experimented and discovered the following:

.wav files
Using POILoader version 4.65.0.0 without sox.exe, trying to load .wav files for proximity POIs, POILoader produced errors for every .wav file format I used, and resulting .gpi file did not have sound.

Attempting the same thing with the latest version of sox.exe and associated .dlls produced different errors, and .gpi file did not have sound.

Attempting the same thing using sox.exe version 14.0.0.1, I was successful in producing a .gpi file that included the .wav sound.

.mp3 files
I converted the .wav file to mp3 format using Audacity, and in every instance, the sound was incorporated into the .gpi file.

I have not actually tested either format sound in navigating. I determined that the sound was incorporated into the resulting .gpi files by examining the file size of the produced .gpi file. My POI file, in .gpx format, was about 6k, and the sound files were always at least 32k. If the produced .gpi file was 6k, I knew that the sound was not incorporated.

This experiment was done to produce repeatable results. I do recall, however, that I downloaded a .wav file from the alerts library here that worked (in actual navigation) without sox.exe, but I don't remember which one. All others I downloaded produced errors.

Does anyone have the exact parameters for .wav the POILoader will handle without sox.exe? I tried several different bit rates, channels, and encoding, but I was unable to produce a .wav that POILoader could deal with natively.