Tuxdroid has the ability to store sounds internally. A default set of sounds is provided and can be found in the subversion repository under the sounds/original directory.

In order to convert all your audio files in the current directory to /tmp, you can run the following command:
for f in *.wav; do sox $f -c 1 -r 8000 -b /tmp/$f; done

Note that the above command works also for other type of audio file, sox does support most common used format.

You can then upload your sounds in Tuxdroid using the gtdi utility, check the Audio tabs in it. Select your files one by one, click on add for each. When your list is complete, click on Store.

When done, you can play each sounds by clicking their number in gtdi.