ONLY Sound Items using the Windows Audio driver have access to the Equalizer.
The Equalizer (EQ) effect strengthens (boosts) or weakens (cuts) the energy of specific frequency band (frequency ranges: bass to low-mid to high-mid to treble).
Positive Equalizer Band values boost the gain on a given frequency band and therefore increase the overall volume output somewhat. Higher band values will lessen the effect of the Volume slider control and can interfere with Fade-In/Fade-Out to some degree.
Locator: Sound List Editor > Tools > DSP Effects .
The Equalizer Tool is opened from the Actions menu or the Actions toolbar.
The Band Center Frequencies are dependent on the sample rate of your input audio. If you change the frequencies, do not set any frequency higher than the Nyquist Frequency. If an EQ Band frequency exceeds the Nyquist frequency of an audio file, it will be clipped to the Nyquist value. The Sound Mill default EQ Band frequencies are set for 44.1K audio. So, if you mostly work with audio at much lower sample rates (ex. voice audio at 8KHz), you may want to adjust the EQ Band frequencies. The default high end Band (16kHz) may be too high for some audio hardware (graphics card or speakers) to make a perceptible difference to the ear. If so, try lowering it 1KHz at a time until you can hear a change. Also, realize there may be little or no high frequency samples in the audio file itself.
Equalizer Frequency Bands labels (Figure 2) above 1,000Hz are displayed rounded to the nearest tenth (ex 2.0kHz), however calculations are made with the precise frequency values.
Equalize(EQ) DSP effect increases or decreases the gain on the frequency band (8 Bands). It can be used in DSP chains just like any other DSP Effect. You can save EQ DSPs with either 1) the Equalizer Tool, or 2) the DSP Effects Editor.