Using Two Different Sample Rates in Audacity

"I have recorded some tracks in Audacity using the project sample rate of 44100Hz. I also imported a track from a portable device at 16000Hz. All tracks sound fine when played simultaneously. However, when I want to insert an audio into the 16000Hz file, it is
distored. I have 2 questions:

1. Is there a way to integrate the two files into 1 track; and
2. Will I have a problem exporting mixed sample rates to CD?"

Mixing sample rates in an audio project can cause all sorts of problems with your final output. There is an easy fix to your problem, which is to simply resample one of the audio files so that it matches the other files.

Change Sample Rates in Audacity If you are using Audacity 1.3.x, the easiest thing to do would be to resample the 16000hz track to 44100Hz and save it at the new sample rate. Work with the newly resampled track as part of the rest of your 44100Hz project. If you're using an older version of Audacity, you might need to follow slightly more convoluted steps to match sample rates.

If you do the steps above to resample your audio file, you won't have a problem outputting your project to CD, MP3 or any other format. In general, you will very likely get either an error or a section of audio that sounds bad when you try to use mixed sample rates in the same file project.