Yeah, it's lectures, and even for that, it's low quality, but that's the rules...If it's kbps that is MP3, just extremely low quality. (This is spoken word, right? Music sounds like crap at this rate.)
Bounce and dither your source from 24-bit to 16-bit to start, if it's not already there. I'd keep it WAV format still.
Then, it depends on your DAW. I can bounce out from Logic to a 64 stereo/32k mono and if I set the Stereo out to Mono I get that 32kbps file.
Audacity can *export* to fixed rate mono that low, and it's free.
Not sure what that 22050Hz means. Is that max frequency? You could lowpass it to guarantee that, I suppose.
Samplitude does this very nicely.
See attached, first the .wav is converted to 16 bits at 22050 Hz. I would save that to Dtop then plug it back into Sam to do the MP3 smash.
Unfortunately the free Silver version seems to be stopped (but if you can find a download MAGIX will still activate it) but you could download a months demo of Pro X. Magix Music Studio probably has the same converter in it.
Reaper will almost certainly do it but, compared to Sam, I found the process much more "clunky".
Dave.
Thanks.
The thing I don't understand is the 22050Hz. If file is converted to 16 bits, will it always be at 22050 Hz?
My AIMP audio converter doesn't have a separate parameter for Hz, but it does the rest.