FILTERS / EQ
Also known as equalization or EQ, filters are employed to boost or decrease the level in a distinct
range of audio frequencies. The most common filters are the easy bass and treble controls
found on affordable stereo systems, which act on a broad range of frequencies. But other filters
are created to surgically increase or cut quite narrow bands of the audio spectrum. A twelve band
equalizer is extremely common in studios.
SHELVING FILTERS
As the simplest form of filter, shelving EQ boosts or cuts all frequencies above or below a fixed
frequency. A bass shelving filter, also referred to as a low-pass filter, boosts or cuts everything below its
fixed center frequency. Likewise a treble shelving filter, also called a high-pass filter, boosts or
cuts everything above its fixed center. A single control generally adjusts the quantity of boost or
cut.
These filters are valuable for creating broad changes like decreasing boomy bass and wind noise. But
encoders can effortlessly be overloaded by too significantly bass or treble, so it is frequently wisest to use these
filters to cut high and low frequencies to stop artifacts.
BANDPASS FILTERS
These filters can be utilised to increase or cut audio on both sides of a center frequency. Bandpass
filters are commonly employed as midrange filters, due to the fact they have small effect on either high or
low frequencies. The familiar graphic equalizer is just a set of bandpass filters tuned to different
center frequencies.
Far more sophisticated versions, called sweepable bandpass filters, have an extra control
permitting you to change the center frequency. Bandpass filters are helpful for growing the
intelligibility of a speaker without increasing hiss or background noise. A variation of the
bandpass filter is the notch filter, which boosts or cuts all frequencies except those around the
center frequency.
PARAMETRIC FILTERS
A parametric filter is a bandpass filter with an additional control to adjust the width of the
frequency band becoming effected . These are the surgical tools of audio editing. They can be utilised to
get rid of just the noise from an air conditioner, while having a minimal effect on the rest of the
audio.
With all filters it is crucial to follow the audio engineer’s 1st rule of EQ — cut rather than
boost wherever feasible. Cutting undesired sounds is always less obtrusive, and boosting too
significantly can make a track too loud and lead to distortion and artifacts when encoding.
COMPRESSORS
A compressor’s fundamental function is to decrease the dynamic range of an audio recording, which is the
difference between the loudest and softest sounds that pass by means of the recording chain. Basically
put, a compressor is a processor whose output level increases at a slower rate as its input level
increases.
By lowering the volume of the loudest sounds, a compressor lets you raise the level of the whole
audio track, generating it all sound louder than it truly is. Compression can be a big help in
achieving intelligible audio tracks with a more uniform volume that will survive the encoding
process. A compressor consists of a level detector that measures the incoming signal, and an an
amplifier whose gain is controlled by the level detector.
A Threshold control sets the level at which compression begins. Below the threshold, the
compressor acts like a straight piece of wire. But when the input level reaches the Threshold,
then the compressor begins reducing its output level by an amount determined by the Ratio
control.
The Ratio control establishes the proportion of alter between the input and output levels. If
you set the compression Ratio to 2:1, then when the input signal gets twice as loud, the output
signal will boost by only half.
If you set the Ratio to its maximum (10:1 or far more), the the compressor becomes a “limiter” that
locks the maximum level at the Threshold.
Although a compressor can level out a recording, high levels of compression can also introduce
artifacts which includes “pumping”, in which there is an audible up and down alter in volume of a
track, or “breathing”, which sounds like someone breathing as the back ground noise level goes
up and down.
EXPANDERS
An expander is the opposite of a compressor. As the level of the audio signal gets louder, the
expander’s amplifier turns up further making loud signals even louder. An expander can be utilised
to reduce noise in a method referred to as downward expansion. In this case you set the Threshold just
above the level of background noise. The expander will then raise the volume of every thing
above the Threshold, but won’t change anything below the Threshold, thereby lowering the
perceived background noise.
NORMALIZING
Normalizing increases the gain of the audio file until its loudest point (or sample) is at maximum
level. The overall signal level is now greater, which makes for clearer audio, and also gives the
encoder a lot more bits of data to function with and reduces encoding artifacts. The only downside of
normalizing is that it increases the noise as well as the audio signal so it should be utilised carefully.
It should be your last step just before encoding, and you might not will need it at all.
MASTERING
Mastering your finished audio item is considered somewhat of an art. There are audio
mastering engineers who get paid a hefty sum of cash to master an audio project for you.
With the equipment available these days you can do a decent job of mastering your project yourself if
you are careful. Some crucial parameters as explained above support professional style mastering
and are summed up below.
Dynamics: This essential step is also termed as compression. Your music requirements to breath and
flow. You do not want to compress it so difficult that it roars back at you. Locate a very good medium
where your music has that fine line between volume and dynamics. The most agreeable
compression ratio is 2:1.
Equaliser: Your songs were probably recorded over a period of time therefore they most likely
will have a slightly various feel to them. You need the songs to sound enough alike that they
feel like they belong on the very same CD. You do not want the bass pumping loudly in 1 song and
the next track finds the listener turning up the bass knob on his stereo. Attempt to get an even feel for
the entire CD.
Same Volume: The volume of each song needs to be about the very same. The general thought on this
is you do not want the person listening to your CD to have to turn the volume up or down. Your
listener ought to be able to listen to your CD at whatever volume they are comfortable with. The
answer is normalization across all the tracks on a CD.
Order of Songs: The order you choose for your songs is important. You will need to be aware of the
feel of each song. You want to take your listener on an emotional roller coaster and the order of
the songs has every thing to do with this ride.
Burn to CD: This final and very essential step is to burn your master to a CD and listen to it on
as many diverse varieties players as you can. Listen to it on everything from a affordable boom box to
a high dollar stereo. Make certain it sounds as good as possible on every 1. The bass is especially
troublesome to get right. Do not get tempted to increase low notes too significantly.
Conclusion
Mastering your recording is 1 of the most misunderstood issues in pc recording. No one
seems to actually know what mastering is. The actions you take to master your audio are not all that
tough, you just will need to go slow, use prevalent sense and most important of all is to listen to your
results. Be careful and take it a step at a time and you can come out with a decent master.

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