Exported audio sounds different than on timeline

I today had another issue:

My De-Noising was active, but it was not exported. I never had this before. After hours of research I set it from strong to weak noise cancelling (it is in german, so I am not sure about the very right names of the settings in englisch) then back to strong noise cancelling. All problems solved.
Everything was correct, all the time... It simply was not applied and you no way you could see it 😞

I have the excact same problem but for some reason it only happens when I have headphones in... once I take the headphones out, the premire pro video and the exported video sound the same, but with headphones in they sound sooo different. 

This was the answer for me. It was driving me a little crazy but when I read this post I checked the audio volume level on my VLC player and it was at 70% I clcked the Increase Volume  choice under the audio tab several times and got it to 100%. At this point the volume on the timeline matched the colume on the VLC player of my exported video. Thaks a million.

How exactly are you listening to the exported file?

When I am editing the voiceover in Premiere Pro it sounds pretty good, but after I export the video to an mp4 it sounds like I'm speaking in a large empty auditorium.

You are preview and editing the audio in the same condition that you recorded it.  An echoing room.  The playback is showing the reality back to you..

Not a normal thing.

So how about some information, so all us volunteers out here aren't having to spend a lot of time guessing?

Basic data on the hardware ... computer, OS/CPU/RAM, and for this your sound gear ... special sound card, system sound, what do you use?

Next, a screen-grab of the Sequence settings for audio track setup, then grabs of both Audio tab sections of the Preference settings, Audio and Audio Hardware. And also one of the Export dialog box for the export you're creating.

Neil