I was looking for a way to convert a Whatsapp audio to an MP3 .. .and here's how I got it to work.
Step 1: Load up your Whatsapp Web so that you can download the Whatsapp audio onto your computer.
Step 2: After you've downloaded your Whatsapp audio, open this website – http://audio.online-convert.com/convert-to-mp3
Step 3: Choose the Whatsapp file and upload it.
Step 4: Click Convert File
Step 5: Look for the file… it just downloaded to your computer!
That's it! You've successfully converted your Whatsapp file into an Mp3.
Once I did this conversion I also added Royalty Free Music to the audio.