Can you elaborate on what you mean when you say you want to "preview" these kinds of audio files?
For example, do you mean you just want to download beginning of the file but not the entire file? In that case, note that the /2/files/download endpoint does support "range retrieval requests", so you can download a partial portion of the file, like this:
# this downloads just the first 10 KB of the file
curl -X POST https://content.dropboxapi.com/2/files/download \
--header "Authorization: Bearer ACCESS_TOKEN_HERE" \
--header "Range: bytes=0-10000" \
--header "Dropbox-API-Arg: {\"path\": \"/Testing/Audio/Laughter.mp3\"}" > out.mp3
