This forum is for technical questions and answers. The most common questions and answers will be added to the FAQ page of FUSE (https://fusecorpus.eu/faq/).
The exam audio file upload instructions mention the following audio file types as acceptable: ogg, m4a, mp3, wav, wma
This means that the file extension after the recording title has to be one of those mentioned above (e.g. recording.mp3). The recording device (mobile phone, voice recorder etc.) will set the file type automatically or according to user specified settings. There is a link to a table below in which one can see certain measures related to mp3 files.
Table of mp3 file measures
Leave a reply if you need help with transforming file formats and I will help you as soon as possible.