categories of audio effects
DESCRIPTION
This lesson is for week 3 of Introduction To Music Production at Coursera.org. I will be teaching "categories of audio effects" including which plugins go in each category and which property of sound each category relates to.TRANSCRIPT
Hi, I am Rasheeq Rayhan from Dhaka, Bangladesh. This lesson is for week 3 of
Introduction To Music Production at Coursera.org. I will be teaching categories of
effects including which plugins go in each category and which property of sound
each category relates to.
There are basically three categories of audio effects we use in the signal flows of
DAW (Digital Audio Workstation). The process is called DSP (Digital Signal Processing).
They are generally related to three of the principles of sound. They are:
1. Dynamic Effects
2. Delay Effects
3. Filter Effects
1. Dynamic Effects:
Dynamic effects play a crucial role in modern mixing. They are designed to alter the
dynamic range of an audio signal. They are important because they allow you to control
the ratios between high and low peaks in dynamic of an audio track over time. Dynamic
effects are related to “amplitude”.
These types of effects are more often used on live acoustic instruments than on
synthesizers and therefore their applications in a sequencer/MIDI environment is
somewhat limited.
There are four main dynamic effects:
• Compressors
• Limiters
• Expanders
• Gates
In the following table, I have listed their main features and applications.
Effect Description Comments
Compressor Allows you to reduce the
dynamic range
(difference in amplitude
between high and low
peaks) of an audio signal
Useful in situations where
the audio signal has a
very large dynamic range
Limiter Represents a drastic
version of a compressor
where the ratio is set
extremely high
Used mainly during
tracking in order to avoid
distortion and during
mastering to maximize
the overall volume of the
mix
Expander The exact opposite of a
compressor. It allows you
to increase the dynamic
range of an audio signal
Sometimes useful to “re-
generate” a track that
was over compressed
Gate An extreme application of
an expander where the
ratio is set extremely high
Very useful to reduce
unwanted noises during
“silent” passages of an
audio track
In the following figure you can see a diagram showing the effect that a compressor
has on a generic waveform. Notice how the gain parameter is set to boost the overall
level of the signal in order to bring back its highest peak to its original value.
Look at the following figure to see how a noise gate would alter a generic
waveform.
2. Delay Effects:
A delay effect is similar to an echo, in that the sound is repeated (after a brief time
delay) one or more times after the original sound. If the time between the original
signal and the repeated (delayed) signal is sufficiently small, it will not sound like a
distinct echo, but rather as a simple reverberation effect to represent spaces that you
are inside.
Delay effects are related to “propagation”. So, if you want to give the listener the
sense that a particular audio was recorded in a large room or a small room you would
turn to a delay effect to give that. The three dimensionality of an audio track has a large
to do with the delay effects.
This effect uses a RAM buffer to store the audio for a certain amount of time, after
which it outputs this audio. The RAM buffer will not always be just large enough to
store the amount of audio set by the current delay time, but will actually be
considerably larger sometimes, because many delay effects allow for their delay
parameter to be automated.
There are five main delay effects:
• Reverbs
• Delays
• Phasers
• Flangers
• Choruses
A Reverb simulates the component of sound that results from reflections from
surrounding walls or objects. It is in effect a room simulator.
A Phaser (also known as a phase shifter) is an audio signal processing technique
used to filter a signal by creating a series of peaks and troughs in the frequency
spectrum. The position of the peaks and troughs is typically modulated so that they
vary over time, creating a sweeping effect.
A Flanger is an audio effect produced by mixing two identical audio signals
together, with one signal delayed by a small and gradually changing period, usually
smaller than 20 milliseconds (kept below the threshold of echo perception). This
produces a swept comb filter effect: peaks and notches are produced in the resultant
frequency spectrum, related to each other in a linear harmonic series.
A Chorus is a delay for which the delay time is modulated by a Low-Frequency-
Oscillator (LFO). The most used LFO waveforms are sine and triangle. The effect can
produce interesting sounds, one of which is to produce the illusion of more than one
instance of the instrument/vocalist being present. What you get out of this effect
largely depends on your desire to experiment.
3. Filter Effects:
A filter effect is a frequency dependent amplifier circuit, working in the audio
frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications
including graphic equalizers, synthesizers, sound effects, CD players and virtual reality
systems. In its most basic form, an audio filter is designed to amplify, pass or attenuate
(negative amplification) some frequency ranges. Filter effects control the “timbre” of
the sound.
Common types include:
• Low-pass filter: passes through frequencies below its cutoff frequencies, and
progressively attenuates frequencies above the cutoff frequency.
• High-pass filter: passes high frequencies above the cutoff frequency,
progressively attenuating frequencies below the cutoff frequency.
• Band-pass filter: passes frequencies between its two cutoff frequencies,
while attenuating those outside the range.
• Band-reject filter: attenuates frequencies between its two cutoff frequencies,
while passing those outside the 'reject' range.
• All-pass filter: passes all frequencies, but affects the phase of any given
sinusoidal component according to its frequency.
I hope you enjoyed the lesson as much as I enjoyed making it. If you have any
questions do not hesitate to discuss with me so we can learn together! Thank you for
critiquing. Also, if you want to know more about my music, please visit my YouTube
channel. J
https://www.youtube.com/user/FrenzyPhrenesis
Regards, Take Care and Happy Learning!
*Word count: 998