Often, one will want to edit the Audio on the Timeline, in another application, like Adobe Audition. Premiere versions allow for this to be done easily, and with exacting control.
Let's say that one has dozens of edited Clips on the Timeline, and they wish to edit ALL of the Audio. * Editing those individual Clips is easy, but how does one edit them all in one file, which will then replace the original Audio in the Clips?
The best way to accomplish this is to Export, or Share the Timeline as an Audio Only file. This Export/Share will be slightly different, depending on the exact Premiere program, and even on the version of that Premiere Program. Often, the Audio-only Export/Share is from the MS AVI Export/Share screen. One would choose Export Audio, leaving Export Video unchecked. If Multiplexing does not automatically set to "None," choose that now.
For this "round-trip" process, the Audio file format is very important. The ideal choice of Export/Share is PCM/WAV @ 48KHz 16-bit. This will yield an uncompressed Audio file, that almost every Audio editing program will easily handle, and is also the format, that one will want to Export, or Save from the Audio editor, for the second leg of our round-trip.
Import, or Open that resultant PCM/WAV in the Audio editing program, and edit, as is needed. When done, just Export, or Save (depends on the program) that edited Audio as a PCM/WAV @ 48KHz 16-bit. In some Audio editing programs, this will be listed as WAV (Uncompressed). The Sample-Rate and Bit-Depth are important, as the 48KHz and 16-bit are the ideal for any flavor of Premiere, and though Conforming will be necessary for editing, it will be easy on the program, and there will be no issues. Stay away from any compressed Audio formats/CODEC's, like MPEG/MP3. You do not want to throw away precious data at any step. That is why we use PCM/WAV for the Export/Share, and then the Export/Save from the Audio editing program.
When done, just Import that resultant PCM/WAV into Premiere. Wait a moment for all Conforming to complete, and then drag that WAV to the Timeline, on a free Audio Track that matches your WAV's Channel-count, i.e. a 2-channel Audio Track for Stereo, or a 1-channel Audio Track for Mono (these must match in Premiere). For more detail on channel-count and Audio Tracks, see this ARTICLE.
Now comes a personal preference for completing this round-trip. I like to leave my original Audio, just in case I change my mind. Gathering up and Trimming the original Audio can be a tedious task. As I have placed my edited WAV onto an empty Audio Track, I just go to Window>Audio Mixer, and Mute any/all Audio Tracks, containing my original Audio. It's still there, if I ever need it, but is now Muted.
Hope that this helps,
* Sometimes we want part of the Timeline's Audio, but that part spans multiple Clips. There is no need to Export/Share the entire Timeline, and then Trim it. Just set the WAB (Work Area Bar) to the part that we do want, and make sure to choose "Work Area" in the Export/Share settings dialog.
Also, and especially when doing just a segment, covered by the WAB, I like to position the CTI (Current Time Indicator) or Playhead (CS 5.5) at the beginning of the WAB, with Snap ON. As I drag my edited WAV to the free Audio Track, it will Snap into place, right at the beginning of the WAB.