Audio level goes up and down in rendered output [After Effects]
Have you export the audio only from audition &amp; does it have the problem then ? 

Does the audio have a compressor on it? You could use one to keep the levels consistent. 

Are you sending from AE to encoder with the sound file ? Try using premier as a middle man. Bring the AE sequence &amp; Audition project into premier and export from there. Could be that AE is ignoring your mix because it’s AE. Alternatively you could export direct from AE the vision and the audio only from audition and stick the two together in premier.