Equalization Bandwidth …
One of the most useful forms of signal processing and sound shaping is Equalization. This is the process of manipulating sound located at a specific frequency or within a range of cumulative frequencies. Parametric equalizers, often referred to as ‘paragraphic’, provide extended flexibility and customization options based on their ability to control the Bandwidth, or the affected range of predetermined frequencies. The bandwidth setting is commonly referred to a the ‘Q’ adjustment.
Q Bandwidth adjustments are performed in various ways. This of course depends on the design and configuration of your software processor. For example, iZotope’s Ozone mastering plugin allows you to grab left and/or right vertical handles that surround a set filter reference point located at a specific frequency. Dragging the brackets apart form one another will increase the bandwidth. In this case the frequency range affected by the equalization filter will be extended.
This particular method is commonly used to create a gradual roll off when implementing high-pass or low-pass filters. In terms of corresponding numerical references of bandwidth settings, the lower the number, the wider the band. In this particular example, a Q setting of 0.60 would yield a gradual roll off.
Often times we are faced with problematic sound issues that live at a specific frequency that is in need of correction. In this case a ‘notch’ filter [see graphic] would be a consideration. This is simply a cut or boost in level at a specific frequency with a narrow bandwidth setting that will zero in on the specified frequency that needs to be addressed. A typical Q bandwidth setting in this particular situation would be 12.0. The higher the bandwidth setting, the narrower the affected range.
Ozone also provides numerical adjustment options of Q Bandwidth. Simply click a specified frequency point and manually key in numerical references in a table for both bandwidth settings and level adjustments. This method provides pinpoint parameter options when necessary.
Equalization is a powerful process that is often misused. I suggest that you use it sparingly. Also, practice bandwidth manipulation. You may find that a slight adjustment in range as opposed to level may help you achieve the results that you are striving for.
Nice post…
I like the angle – addressing specific audio editing and processing techniques within the context of podcasting on your blog – nice.
I’d like to mention to any readers that there are many paragraphic EQ’s out there with Q settings, for those of you looking for other options (in case you didn’t get that!)
Also, in addition to hi passing / lo passing and the other extreme – notch filtering (like in the image above) – there’s alot to be done with ‘mid Q’ settings, especially in the cleanup phase. Subtractive EQ’ing would likely be a good topic to cover here…
Anyway, thanks and enjoy. =]
Dan mentions it in passing in his comment but it’s worth pointing out that the screenshot shows a notch filter, not a high-pass or low-pass filter as the text implies.
Craig,
Both my text and Dan’s comment point out that the graphic is in fact an example of a notch filter.
What text are you referring to?
-ptfigg.