Getting Audacity to convert to MP3 using ABR

[ulillillia]

Originally posted by Psythik
Yes, Creative's MP3 players support both ABR and VBR, but if you're converting from MP3 to MP3, you're just gonna end up with even worse sound quality unless you have the original CD or WAV.

I've known that for a long time - I did a test with JPGs, which are similar to MP3's, but deal with images rather than audio. Even at a high quality (like 95), after about ten saves, it looks as bad as if quality 60 was used, even though it's got a file size that of what the 95 would have. When I resave into MP3, I replace the old MP3 by converting the original WAV file to MP3 under the same name (causing me to get a warning asking if I want to replace that file or not). The only exception to this is with lossless files, like PNG (to images) and WAV.

Onto my original question now - how do you convert a WAV file, of otherwise random formats, into MP3 with the following specifications:

format: ABR (average bit rate)
bit rate: from 10 to 20 Kbps
sample rate: 11,025 Hz
channels: 1 (mono)

The source WAV files have quite random formats, especially in the sample rates.

format: uncompressed (always the same)
bit depth: in order of most common to least common: 8-bit, 24-bit, and 16-bit. I only encode with the 8-bit and 16-bit formats, whatever the original uses and since MP3 only uses 16-bit, there's not much sense in encoding from 24-bit.
sample rate: varies widely from 15,000 Hz at the extreme low end, to in excess of 150,000 Hz at the extreme high end. Section 3.2 here gives all the speeds I use in a convienient table.
channels: 1 (always the same)

The source WAV files should not be deleted and not all WAV files get converted (as I have a base file from which I get the various speeds from by changing the sample rate). The only thing I'm missing is a way to convert the source WAV files into MP3's as the ABR format.

My link above explains how I process my music and convert it. It mentions Audacity for conversions, but I'm always using CBR, since that's all Audacity seems to support. I need ABR (at least to test it).