So you have used the Adjustment Layer a couple of times and have been wondering how to use it for audio?
The way it works for audio is slightly different. Just Go to the 'Audio Track Mixer' Panel and twirl open that little triangle on the top left. That will open the effects rack where you can apply audio effects to the whole track (A1, A2, A3,... etc.) and even to the Master Track.
This basically works like applying video effects across multiple clips with an Adjusment Layer. The only difference is you can't limit it to a certain segment like you can do with an Adjustment Layer.
