EQ for Smoothing Dialogue Audio shows how to do this in Adobe Audition using the standard Parametric EQ plugin that comes with Audition. But keep in mind, you can do this in almost any audio editing app including Audacity, Garage Band, Logic, Cubase, Pro Tools and others. Read more about audio.
Equalization is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in sound recording and reproduction but there are many other applications in electronics and telecommunications. The circuit or equipment used to achieve equalization is called an equalizer. These devices strengthen (boost) or weaken (cut) the energy of specific frequency bands.
In sound recording and reproduction, equalization is the process commonly used to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. An equalizer is the circuit or equipment used to achieve equalization. Since equalizers, “adjust the amplitude of audio signals at particular frequencies,” they are, “in other words, frequency-specific volume knobs.” Read more about equalization at Wikipedia.