How to get a free and approximate audio transcription via YouTube’s automated transcription:
1. Use the free Audacity or other desktop audio software to split your .mp3 into segments of less than 15 minutes each. I assume that’s still the limit. Or make it whatever time-limit YouTube sets on uploads in future.
2. Upload the .mp3s to YouTube as a “Public” video via TunesToTube. This is a free service that lets you upload an .mp3 to YouTube and quickly add a single picture visual, to become a video which is then uploaded to YouTube.
3. Then go to YouTube and find your Channel, click the Settings cog on the uploaded video, and turn on “Automatic Subtitling”.
4. Wait a minute or so for the subtitles to be made. Then go to DownSub.com to download and save the video’s subtitles as an .srt standard subtitles file.
5. Get the Open Source Subtitle Edit 3.5 desktop software. Load the .srt file. In Subtitle Edit: File -> Export -> Plain Text.
6. Load the resulting text into Word, and edit and correct. It’s accurate enough for a ‘speech radio’ type podcast, though without much punctuation and you’ll need to work on it to polish it up.
You can of course get willing hands around the Web to transcribe, but you have to pay them (it’s surprisingly affordable) and there’s usually at least a 12 hour turnaround time. The above method would help you to meet a much tighter deadline.