written by: Shane Burley•edited by: Rhonda Callow•updated: 6/17/2010
Here is a look at different post-production audio equalization methods that are used to fix audio problems.
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What is Audio Equalization?
When post-production audio mixing is taking place with audio that has always been recorded it hardly ever stays exactly the way that it appeared during initial playback. Instead you want to enhance, correct, or just alter the audio that you have so that the final mix is something that is much more intended. Within this world a lot of different things can be called audio effects, but audio equalization means something fairly specific. Audio equalization indicates a process by which the very frequency response of a given audio signal is altered. In this model an audio equalizer is any signal processor that will complete this task. There are several different types of audio equalization that are actually very common in digital audio production and post-production, and here is a look at a few of them and terms that are associated.
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Low Pass Filters and High Pass Filters
The various "pass" filters refer to different audio equalizers that actually let certain tones pass through while others are restricted. The low pass filter will allow the lower tones while the high ones are taken out. The high pass filter, alternately, lets high tones pass and will block out the low tones. A low pass filter may be great for a high pitch static interference that must be removed, and a high pass filter would be appropriate to remove a low bass tone.
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A graphic equalizer is an audio equalizer that allows for direct frequency control through a graphical interface. You can either lower or raise certain frequency responses with a design based on a graphical format rather than one that is technical, such as a purely numeric one. These interfaces are perfect if you are not exactly sure what type of audio equalization, and at what level, you will need for the given audio effect that you want. The graphical layout will then have things like faders and knobs often, which are essentially representative for how you want to change the actual audio playback after you have shifted it from the digital field recorder or other recording apparatus.
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The term attenuation often refers to the point of an audio piece as it is moving away from its peak. This can tend to mean to decrease the audio in question. More attenuation is in place the further the audio is from its general peak. In the pass filters, such as the low pass filters or high pass filters, restricted audio is attenuated.
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Band Pass Filter
A band pass filter works on the exact same pattern as the low pass filter and the high pass filter in that it restricts certain frequencies while it allows others to pass. The band pass filter is different than the low pass filter and the high pass filter in that it does not just restrict those in the high or low range, but instead just an identified frequency range.