Newbie Question - Signal Display

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I am confused by this section that is lighter color on top and bottom. I don’t know how this happened. My guess is this ‘section’ is constrained for peak amplitude. Please enlighten me. Thanks!

You probably have some “envelope points”. See:

Note that there is a bug in some early Audacity 3.x versions that can create unwanted envelope points. To avoid this, ensure that you are using the latest version of Audacity (currently Audacity 3.0.5: