Effects for sound processing. Composition processing
This article discusses the principles of operation of various devices designed for sound processing.
About how and in which cases it is correct and it is necessary to use them we will discuss further.
The effects considered in the article are divided into the following categories:
Time transformations: delay, echo, reverb, various delays using modulation (phaser, frequency modulation, chorus, flanger).
Frequency Conversion: various types of equalizers.
Amplitude transformations: compressor (limiter, maximizer), expander, amplitude modulation (ripper).
Other conversions: vocoder.
Delay and Echo
Delay (Delay) – an effect that adds to the original signal of its copy with a time delay (more than 0.5 seconds), with your defined repetition frequency (usually a multiple of the tempo) and amplitude attenuation.
There are two types of this effect:
Simple Delay (Simple Delay), uses one delay line of the original signal.
Complex Delay (Multi Delay), uses more than one delay line of the original signal.
An example of a complex delay: repeating a signal in the right channel with a frequency of n and repeating a signal in the left channel with a frequency of 2n.
Delay is a good tool for giving a stereo-effective sound to the composition. When using delay, keep in mind that excessive use of this effect can make the song illegible and it may turn out to be a mess.
If the delay time coincides with the tempo of the music, then the sound depth increases, and the effect remains invisible.
Most sound engineers set the delay time according to the tempo of the song. Delay submits to the pulse of music and he adds space to the sound. It seems that the delayed repetition of the signal disappears, and the sound is smoothed.
Very similar to the delay is the echo effect (Echo). If the delay simply adds its copies to the original signal with certain values of periodicity and attenuation, then in the echo the copies of the signal undergo a spectral (frequency) change.
Did you ever hear an echo in life?
For example, you shouted something and heard a reflection of your scream after a certain period of time.
Why did this happen ?
A sound wave propagates in the air (and not only), encountering obstacles in its path. Depending on the frequency of sound, it can go around this obstacle or bounce off of it. The lower the frequency (the longer the sound wavelength), the better it goes around obstacles. Sound is reflected in various ways from various obstacles, and this is precisely what is taken into account in the Echo effect. Delay just adds copies of the original signal without changing their frequency characteristics.
Reverb is also a sound delay effect, but unlike an echo, the original signal repeats at a much shorter frequency and decays accordingly faster.
If the echo in real conditions can be found in the mountains and on the street, then the reverberation is indoors. A sound wave is reflected from the walls of the room, after which it is again reflected from the walls of the room – and so on until it calms down. Reverb is very distinguishable in long tunnels, caves, churches, in voluminous rooms with poor acoustics (poor acoustics also means the complete absence of reverb, which deprives the sound of its naturalness). Sound differs after the resonance of its source ceases – you hear the reflection of the sound wave from the surfaces of the room. In the beginning, early reflections return to you – directly from the surfaces of the room, then reflections from reflections arrive with less intensity.
Reverb is considered to be according to the formula:
T = 0.164V / A, where V is the volume of the room, A is sound absorption (depends on the material and type of surfaces, their areas). There is a room reverb calculator on the Internet.
Short reverb or short delays add volume to the sound.
Reverb with attenuation less than 1 s and delays less than 100 milliseconds (usually made much shorter) create an acoustic space around the sound, especially if they go through both stereo channels.
Often the reverb decay time is set as low as possible, and for digital devices this is a very difficult task. It may result in a metallic sound. If this happens, you can correct the situation by increasing the decay time, or try another preset that will give a softer sound, or take another reverb that can work with such parameters.
Reverb sounds much better if tied to the tempo of the recording.
The reverb is tuned to the song according to the impact of the working drum, and the decay time is selected so that the sound ends before the next beat. The task is to make the reverb “breathe” with the music.
The best thing is to first do everything as much as possible with a minimum reverberation time, then slowly add time until the reverb is built into the tempo.