Normalize audio? how to?

Since normalization is just applying a constant gain to achieve "optimum" peaks (and that is subjective!) and all you have to do in FCPX is grab the dB line of any audio anywhere and drag it to affect a gain change for any clip or Range selection (with the peaks actually being *visible* -- "hot" peaks turn yellow -- the 0dB reference line is always visible), the necessity of a separate Normalization effect/function/plugin is nil.

Normalization is a "quick fix" and can ruin a scene just as well and more easily as anyone else can -- even "video guys", because it's indescriminate. There are much better filters available (you should check into the Levels > Logic > Adaptive Limiter and probably the EQ > Logic > Linear Phase EQ -- both used for more serious audio "mastering".)

See if this thread helps

https://discussions.apple.com/thread/4185222?answerId=19196680022#19196680022&ac_cid=tw123456#19196680

There is a "Loudness" control in the Audio Inspector > Audio Enhancements > Audio Analysis line (you do not need to have the audio "analyzed and fixed" first. You have to turn on the Loudness by clicking on the square before the label. To do it for a "presentation" - I recommend selecting all the clips in the storyline and typing Option-G (make a compound clip). Loudness will be applied to the entire project that way.

The Adaptive Limiter is a limiter, but more. It can be used to lower the noise floor (Input Scale) and increasing the Gain AND limiting the peaks (-2.0 dB to 0.0 dB digital scale). It can be used to "adjust" the dynamic range much better than simple normalizaiton.

Linear Phase EQ... still is worth checking into... ALL of the Logic EQ plugins have a master gain control. And Linear Phase and the Channel EQ have Pre and Post EQ frequency Analyzers (you have to turn it on though -- there's an Analyzer button on the left side of the interface popup dialog under the Master Gain control). There is also a simple Gain plugin as well and a more complex Multichannel Gain (surround).

While you're at it, you ought to check out the MultiMeter (under Specialized.) It's an Analyzer, Goniometer, and Correlation meter... "all in one" (with "sample and hold")... very useful.

HTH