Equalization

ToDo Needs review by Martyn

Equalization is a way of manipulating sounds by Frequency. It allows you to boost some frequencies and reduce other frequencies. This is a more advanced form of the EQ and Tone controls on many audio systems. As an example of equalization, the curve shown below changes the balance of high and low frequencies in the audio to make it sound like an AM radio broadcast. High frequencies (above 6000 Hz) and low frequencies (below 100 Hz) are reduced in volume by 20 dB.

The Graph

• Vertical sliders: The vertical sliders can be used to give more or less detail on the vertical scales.
• Control 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.???

Parameters

• Draw Curves/GraphicEQ: These two options select whether the equalization is defined by drawing a curve with control points or by using on-screen sliders as in a graphic equalizer. The image above shows the Draw Curves view where a graph of Frequency against Gain is drawn. The image below shows the Graphic EQ, where a set of sliders control the gain at pre-set frequencies. /// needs expanding as this will be most used..... explain graphic EQ is a log view somewhere.. what is the width of the bands..... what is the increment on the sliders...///
• Linear Frequency Scale: It's more usual to have a logarithmic frequency scale as shown above which gives more detail at the lower frequencies. A linear scale can be useful for precision adjustments at high frequencies.
• 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 between pre-set curves that have already been defined.
• Save as: Used to remember a setting you have created as a pre-set curve
• Delete: Used to entirely remove a setting you don't want any more.
• Flat: Quick way to set a "level response curve". This means the curve on the graph is drawn from left to right at 0 dB on the vertical scale, so that no frequencies will have their volume level modified.