Audio issues when exporting video

I work for a small cable TV company.  We insert advertising on national networks (USA, ESPN, etc).  We've had customers call in complaining that some of our commercials are much louder than the network programming.  We receive video files from advertisers and then encode them to put them on our system.  Using Adobe Encoder, I see that there are several audio settings when exporting video.  I am not familiar with all the settings.  Is there a standard I should be using to normalize anything being exported?