Equalization

ToDo Needs review by Martyn

Description and Usage

Equalization is a 'graphic equalizer'. It allows you to boost some frequencies and reduce other frequencies.

The graph shown here makes audio sound as if it is on the radio. High frequencies (above 6000Hz) and low frequencies (below 100Hz) are reduced in volume by 20 dB.

Parameters

• Curves/GraphicEQ: Radio button to select how the parameters are displayed on screen. The image above shows the "Curves" view where a graph of Frequency vs Gain is drawn. "GraphicEQ" provides a sliders-based interface as shown in the image below.
• Linear Frequency Scale: It's usual to have a logarithmic frequency scale as shown here which gives more detail at the lower frequencies. Logarithamic display roughly corresponds to the way we perceive pitch, where as Linear display shows equal frequency ranges on each unit of the scale.
• Length of filter: Sets how much audio Audacity processes with each step. Best left at the default setting. Large values will tend to 'smear out' the sound. Small values will deal less well with low frequencies.
• Select curve: Used to choose built-in curves that have already been defined.
• Save as: Used to remember a setting you have created.
• Delete: Used to entirely remove a setting you don't want any more.
• Flat: Quick way to set a 'level response curve'. This will treat all frequencies the same.

The Graph

• Vertical sliders: The vertical sliders can be used to give more or less detail on the vertical scales.
• Draggable points: Used to change the shape of the curve. Higher means boost this frequency, lower means reduce this frequency.
• Blue Line: This is the curve you've asked for.
• Green Line: This is the curve Audacity will actually use. It's usually pretty close, but the effect cannot deal with very sudden changes. If the curves are very different, check the setting for length of filter. It should not be at an extreme.