Students will be able to understand about the various types of signal processors. Students will be able to choose the signal processors according to the need in studio or live applications. Students will know about the characteristics of signal processors.

1. AUDIOGRAPHY
UNIT – 2 – Signal Processors
PREPARED BY
SANKARANARAYANAN K. B
ASST. PROFESSOR
DEPARTMENT OF VISUAL COMMUNICATION
NEHRU ARTS AND SCIENCE COLLEGE(Autonomous)
COIMBATORE

2. Expected outcomes
 Students will be able to understand about the
various types of signal processors.
 Students will be able to choose the signal
processors according to the need in studio or
live applications.
 Students will know about the characteristics of
signal processors.

3. Topics Covered in this Session
 Signal Processors
 Characteristics
 Types & Uses

4. Signal Processors - Introduction
 Audio signal processing is the electronic
manipulation of audio signals either analog or digital.
Audio signals are electronic representation of sound
waves—longitudinal waves which travel through air,
consisting of compressions and rarefactions. The
energy contained in audio signals is typically
measured in decibels.
 Analog processors operate directly on the electrical
signal, while digital processors operate
mathematically on its digital representation.

5. Types
 Spectrum Processor (Frequency)
 Time Processor (Intervals)
 Dynamic Processor (Amplitude)
 Noise Processor (Noise gate)

6. Spectrum processor
 A spectrum processor is a device that displays
signal amplitude (strength) as it fluctuate by
signal frequency. The music industry
uses spectrum analyzers to examine the frequency
spectrum of audio signal either while recording or
mixing. Eg : Equalizer
An Analog spectrum processor (dbx 215 Dual channel Equalizer)

7. Digital Signal Processor ( Fabfilter Pro-q) used as VST Plug-in
in DAW’s
 Image Source: https://www.google.com/url?sa=i&url=https%3A%2F%2Fsplice.com%2Fplugins%2F128-pro-q-vst-au-by-

8. Time Processors
Time Processors are used to change or alter the time
of audio signals such as reverberations or delays
etc. It can also alter the time interval of an audio
signal and its repetition.
Eg: Reverb, Delay, Phaser, Chorus, Flanger etc.
The Analog Stereo Reverb/Effects Processor delivering Lexicon reverbs, delays
LEXICON PCM 96

9. Time Processors
Waves R-verb the digital VST Plug-in used in DAW’s
https://www.google.com/url?sa=i&url=https%3A%2F%2Ftheproaudiofiles.com%2Freverb-plugins-for-mixing%2F&psig=AOvVaw1vV_sDLu2hCYSElpl-
Igub&ust=1594014532548000&source=images&cd=vfe&ved=0CA0QjhxqFwoTCIDbtIe1teoCFQAAAAAdAAAAABAD

10. An amplitude processor or a dynamic processor
affects the dynamic range of the audio signal.
Eg: Compressor, Limiter, Maximizer, Expander etc.
Amplitude Processors
Dangerous Compressor ( Outboard Equipment)

11. Amplitude Processors

12. Noise Processors
A noise gate or gate is an electronic device or software that is used to
control the volume of an audio signal. In its simplest form, a noise gate
allows a main signal to pass through only when it is above a set
threshold: the gate is "open". If the signal falls below the threshold, no
signal is allowed to pass (or the signal is substantially attenuated): the
gate is "closed“.
Drawmer DS404 Quad Channel Gate

13. Noise Processors
Waves Z-Noise Noise Reduction Plug-in

14. Audio effects (Wikipedia)
 Audio effects are systems designed to alter how an
audio signal sounds. Unprocessed audio is
metaphorically referred to as dry, while processed audio
is referred to as wet.
 delay or echo - To simulate the effect of reverberation in
a large hall or cavern, one or several delayed signals
are added to the original signal. To be perceived as
echo, the delay has to be of order 35 milliseconds or
above.
 Analog echo effects are implemented using tape delays
or bucket-brigade devices. When large numbers of
delayed signals are mixed a reverberation effect is
produced; The resulting sound has the effect of being
presented in a large room.

15.  Flanger - to create an unusual sound, a delayed signal
is added to the original signal with a continuously
variable delay (usually smaller than 10 ms). This effect
is now done electronically using DSP.
 phaser - another way of creating an unusual sound; the
signal is split, a portion is filtered with a variable all-pass
filter to produce a phase-shift, and then the unfiltered
and filtered signals are mixed to produce a comb filter.
 chorus - a delayed version of the signal is added to the
original signal. The delay has to be short in order not to
be perceived as echo, but above 5 ms to be audible. If
the delay is too short, it will destructively interfere with
the un-delayed signal and create a flanging effect.
 De-esser - control of sibilance in speech and singing.

16.  Often, the delayed signals will be slightly pitch shifted to
more realistically convey the effect of multiple voices.
 equalization - frequency response is adjusted
using audio filter(s) to produce desired spectral
characteristics. Frequency ranges can be emphasized
or attenuated using low-pass, high-pass, band-
pass or band-stop filters.
 timescale-pitch modification - this effect shifts a signal
up or down in pitch.
 resonators - emphasize harmonic frequency content on
specified frequencies. These may be created
from parametric equation or from delay-based comb-
filters.

17. Analogue v/s Digital
 Analog equipment that exhibits high bandwidth,
non-linear behavior presents the biggest challenges
in creating accurate models,” he said. “But it’s often
the sound of these non-linearities that makes the
original analog equipment so desired.
 When using plug-in, many recordist miss the “feel”
of analog hardware. Interestingly, this is often age
centric. Most younger people without analog
experience tend to gravitate toward plug-in because
it’s all they know. But for audio veterans, it is hard to
forget the subtle satisfaction that comes when the
tape speed on a machine fluctuates ever so slightly.
For More Info: https://www.youtube.com/watch?v=7cuheEuW5Bc
Producer Jack Joseph Puig surrounded by hardware components in his studio.
Source : https://www.thebroadcastbridge.com/content/entry/8314/plugins-vs.-hardware-an-argument-for-the-ages

18. Summary
 Audio signal processing is a subfield
of signal processing that is concerned
with the electronic manipulation
of audio signals
 It can be used to process the audio
as both analog and digitally.
 Signal processors are used in audio
chain in order to give special effects
for the dry audio.

19. Points to Remember
 An analog audio signal is a continuous signal represented by an
electrical voltage or current that is “analogous” to the sound waves
in the air. Analog signal processing then involves physically altering
the continuous signal by changing the voltage or current or charge
via electrical circuits.
 A digital representation expresses the audio waveform as a
sequence of symbols, usually binary numbers. Most modern audio
systems use a digital approach as the techniques of digital signal
processing are much more powerful and efficient than analog
domain signal processing.
 Processing methods and application areas include storage, data
compression, music information retrieval, speech
processing, localization, acoustic detection, transmission, noise
cancellation, acoustic fingerprinting, sound recognition, synthesis,
and enhancement (e.g. equalization, filtering, level
compression, echo and reverb removal or addition, etc.).

20. Source for Reference
 https://www.youtube.com/watch?v=M4GRBJJ
MecY
 https://www.youtube.com/watch?v=X0LpluJsz
Qs
 https://youtu.be/vFwsJYKQmTA
 https://www.waves.com/plugins
 https://dbxpro.com/en/product_families/dynami
cs-processors
 https://dbxpro.com/en/product_families/equaliz
ers

21. Introduction of Next Session
 Cables and Connectors-XLR, TRS, TRRS,
TS, RCA, SPDIP, AES/EBU and fiber optic
 Cables and Connectors.

22. Thank You
SANKARANARAYANAN K. B
ASST. PROFESSOR
DEPARTMENT OF VISUAL COMMUNICATION
NEHRU ARTS AND SCIENCE
COLLEGE(Autonomous)
COIMBATORE
Mail Id:
nascsankaranarayanan@nehrucolleges.com