I hope this is the right place to post a topic such as this. To be honest, I only have a small observation but I wonder what other users think.

It seems to me that the lowpass filter included with Audacity - in the form of a Nyquist script, I believe - doesn't provide such a hard or effective cutoff as could be expected. Is this observation right? LAME is about the closest I've got to any other lowpassing software but I wonder how Audacity's built-in filter performs.