8.1 Introduction
Dry Signal - Wet Signal
8.2 Why Use Signal Processing Effects?
Reducing Hiss
Hiss describes a high frequency noise inherent in the analog recording process. Hiss is heard by the human ear within the frequency range of 2 to 8 kHz. Turning down the frequency settings closest to this range can attenuate hiss.
Recording With Hiss
Hiss Diminished With Equalization
Reducing Hum
Hum is a low-frequency problem associated with leakage of the 60 hertz AC electrical current into the audio signal. A poor ground in an electrical circuit can cause hum. Attenuating frequencies right around 60Hz would lessen the problem.
Recording With Hum
Hum Diminished With Equalization
8.5 The Graphic Equalizer
A Simple Graphic Equalizer
8.7 Audio Filters
Low, High and Band Cut/Pass Filters
8.8 Noise Reduction
Using Dolby to Reduce Analog Tape Noise
Dolby noise reduction is commonly built into cassette and reel recorders. The system relies on companding: compressing an audio signal during recording and then expanding the signal during playback.
Recording Without Dolby
Recording With Dolby
8.9 Reverb and Digital Delay
Digital Reverberation
The reverberation unit manipulates the sound signal to artificially produce the sound of different acoustic environments. Sound heard (or produced) in a small studio sounds different than sound produced in a large hall or auditorium, and reverb is the main characteristic that audibly produces the difference.
Digital Delay
A digital delay, as its name implies, takes the audio signal, holds it, and then releases it to allow the signal to be used further. The time the signal is held or delayed can be varied from fractions of a second to several seconds.
8.10 Dynamic Range
20 Decibels - Whispering
The dynamic range goes from 0 decibels at the threshold of hearing to 120+ decibels at the threshold of pain. A whisper is around 20 decibels, normal conversation is near 60 decibels, and shouting is about 80 decibels. Average music-listening levels are between 30 and 80 decibels.
60 Decibels - Talking
The dynamic range goes from 0 decibels at the threshold of hearing to 120+ decibels at the threshold of pain. A whisper is around 20 decibels, normal conversation is near 60 decibels, and shouting is about 80 decibels. Average music-listening levels are between 30 and 80 decibels.
80 Decibels - Shouting
The dynamic range goes from 0 decibels at the threshold of hearing to 120+ decibels at the threshold of pain. A whisper is around 20 decibels, normal conversation is near 60 decibels, and shouting is about 80 decibels. Average music-listening levels are between 30 and 80 decibels.
8.11 Compressors, Expanders and Noise Gates
These devices affect the volume of a signal and are most often used to process the signal between the studio and the transmitter. They were the first processing devices used in radio. They are also used in the production room to process the signal before it’s sent to an audio recorder.
Dry Signal
This is the original, dry recording. Click on the other play buttons to compare the dry signal with compressed, expanded and noise gated wet signals.
Compression
The compressor operates as an automatic volume control and reduces the dynamic range of an audio signal put through the unit. It is usually utilized to make a sound that has both quiet and loud parts have a more even volume throughout.
Expansion
An expander is essentially the opposite of a compressor and therefore is used to expand the dynamic range of an audio signal. It can make quiet parts quieter and louder parts louder.
Noise Gate
A noise gate is a type of expander used to reduce noise by heavily turning down the level of an audio signal that falls below a set threshold point. In this example we have the threshold set high so that all but the loudest sections of the music are nearly cut out.
8.13 Other Signal Processors
Flange
A flanger is another processor for producing a specific special effect. This unit electronically combines an original signal with a slightly delayed signal in such a way as to cause an out-of-phase frequency response that creates a filtered swishing sound that has peaks and valleys over time.
Dry Sound
Sound With Flange
De-Esser
A De-esser is an electronic processor designed to control the sibilant sounds without affecting other parts of the sound signal.
Dry Sound
De-essed Sound
Projects
Project 1: Record Commercial with Signal Processing
Download the music project files Download the sound effect project filesClick above to navigate to the Music folder, where you will find various music files you can use for this project. Note the file location if you wish to import it directly into your audio editing application.
Please note: The music and sound effect project files only need to be downloaded once and used for all projects.
Project 2: Create chorus effect with multitrack layering
Download the music project files Download the sound effect project filesClick above to navigate to the Music folder, where you will find various music files you can use for this project. Note the file location if you wish to import it directly into your audio editing application.
Please note: The music and sound effect project files only need to be downloaded once and used for all projects.
Project 3: Restore an audio clip with unwanted noise
Download the music project files Download the sound effect project files Download the project specific filesClick above to navigate to the Music folder, where you will find various music files you can use for this project. Note the file location if you wish to import it directly into your audio editing application.
Please note: The music and sound effect project files only need to be downloaded once and used for all projects.