I think I understood what is happening: the .mp3 files you collected are not blank, they just use a non-mpeg codec. It’s my fault: at the time I created the voiceRecorder element I was confused about audio-encoding specification and I thought that my code output proper MP3 files. But I just tested collecting recordings again today and when I look at the properties of the mp3 file from the uploaded archive, it says “Codec: Opus.” I’m sorry about that, my apologies for the inconvenience.
If you still have those .mp3 files, here are a couple things you can try. First, try renaming them so they have a .ogg extension instead of .mp3. If that doesn’t work, it means that the software that you use to open audio files does not support the Opus codec. I suggest you download VLC media player, it has great codec support and it’s free and open source.
If that works, then you can go ahead and collect audio recordings. Just remember to use .ogg/VLC.
I will fix the encoding issue in the next release of PennController
Jeremy