You should be able to hear the drop in levels with either the Constant Power, or the Constant Gain Audio Transitions. Hearing the difference between them can be a bit more difficult. Not sure why you are not hearing these. As a test, increase the Duration of one and listen carefully.
As for making your own Transitions, that is basically what you are doing with the Keyframes on Volume in the Effects Control Panel.
The other way would be to attenuate the Levels in the file in Soundbooth/Audition.
It sounds like you want the equivalent of an audio "dip to black"; in other words, you want the outgoing audio to ride from 100% volume down to 0% volume, and then the incoming audio to ride from 0% back to 100% volume. Unfortunately, there is no built-in audio transition that does this--they all function as crossfades with the volume from both audio clips being mixed during the entire duration of the transition.
Thankfully, there's a pretty easy and versatile solution, though it does involve a little setup legwork on your part. When in doubt, roll yer own
- Drop an audio clip or a video clip with audio into a sequence, and go to the beginning of the clip.
- With the clip selected, create a fade in using two volume keyframes, to the duration you desire. You already mentioned that you know how to rubberband the volume, and that's all you're doing here. You can either set this up in your sequence, or the effects control panel, whichever is easier for you. You can also Control+click the keyframes to turn them into Bezier keyframes, so that you can ease in and out of the keyframes, if you like.
- In the effects control panel, under Audio Effects, right-click on the word "Volume", and select "Save Preset". In the dialog that appears, name your preset (i.e. Volume Fade In 1 second), select Anchor to In Point, and add a description if you like. When you hit OK, the preset will be saved in your effects bin under Presets, where you can categorize them later.
- With this done, select the keyframes you created and delete them, or toggle the stop watch on and off to remove the keyframes. If you do the latter, you'll need to hit the keyframe button to remove the keyframe that is automatically keyframed.
- Repeat steps 2 and 3 above but instead of creating a fade in, create a fade out using the same techniques. Save the preset again using the same procedure, but selected Anchor to Out Point, and change the name to reflect that it's a fade out.
- You'll now have two custom fades in your Presets bin. You can select all of your clips that you want to apply the fades to and drag first one preset and then the other onto all of the selected clips. The reason you need to create two presets instead of one is because you probably want to maintain the duration of your fades, and the only way you can do this is to select the "Anchor to" options. If you created a fade in and fade out on one clip and selected Scale, the duration of the fades would be based on the duration of the clip; not likely what you want.
Hope that helps a bit...
You can also just leave a gap between the clips as you apply the current preset fades, then bring the clips together.
Thankfully, there's a pretty easy and versatile solution, though it does involve a little setup legwork on your part. When in doubt, roll yer own"
Very detailed and helpful reply.
All good input here... thank you