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(:E cries at...

Hernan's Blog of Hate!

[ Friday, May 16, 2003 ]



Well, this one's for not so dummies. To understand this part of the guide, you probably need to remember something about waves, as learned through Physics 2 back in the university. :)

Well, today's lesson is about common effects. An effect is some kind of manipulation done over the characteristics of a wave or signal, like its amplitude and its phase, and some of this processes include wave add/substraction, frequency filtering, etc.

Effects that manipulate the gain of a signal:

Volume envelope: The most simple. Controls the general output of the signal. Often used as a general parameter that affects the wave amplitude of the whole production. You all have messed up with volume right?

Equalizer (EQ): Its concept it's simple. Its concept. The idea of equalization is to boost or cut (increase or decrease the gain) of certain range of frequencies in the sound. The term equalizer comes from initial needs to flatten the frequency response. The frequencies dealt with here, correspond to the human hearing frequency range (aprox 20 to 20000 Hz).

Compression/Limiter: Reduces the dynamic range of a signal. The dynamic range is defined from the lowest intensity of the signal to its highest intensity, so what the compression does is balancing intensities, so that the signal flattens. Compression is usually set as a ratio, for example a 2:1 ratio means that, in order to increase the level by 1 decibel, the input should have a 2 decibels level increase. 10:1 ratio is called a "Limiter" effect, where no changes in level will be allowed.

USES: This is used extensively in every recording:
- to flatten the original signals so that the mixing process is much less a pain in the ass.
- to make decay less obvious: when a string in the guitar is plucked that's called "attack", the highest level of the signal is produced here, then the sound begins decaying. Compression can even decay so it becomes less noticeable.
- to level the signal of a singer who moved constantly away and to the microphone.
- Sometimes the effect of compression on the signals reduces the need for equalization, as it sometimes is used to give punch or power to a wave (like that of the drums).
- you can hear high levels of compression when hearing one of those typical radio stations. Their waves usually have at the same time a "DJ" talking physical trash and a musical background curtain. The DJ signal in the mix is much higher than the curtain's, so when the DJ stops talking shit the curtain begins gaining up. When the DJ comes in again, the curtain disappears.. and it's a sickening loop.
- This effect should be used with care when recording certain types of music, where dynamics are really important, like jazz, or classical music, where a lot of expression (accents) occurs from the musician's playing, or it could destroy the whole "feeling".

Expansion (Noise Gate): Reverse to Compression. Atenuates lower frequencies (can make them disappear) and leaves louder frequencies intact. Acts as a variable gain. When the signal level it's higher than some specific threshold the gain will stay intact, but when the signal level is lower than the threshold the gain will decrease. The effect is used mainly in noise reduction. Actually, Pantera did include a lot of it back in the "Vulgar Display of Power" days, to make stops as dry as it gets, a distinctive of those days' "power metal". High expansion (10:1 proportion) it's called "noise gate", where only the levels above the threshold get to sound, used a lot in wave synthesis (on next rant please).

De-esser: This effect reduces the excesive "sss" sound, through a compressor effect, but it doesnt define a threshold, it only monitors certain frequencies (the frequencies generated by an "ss" sound).

Effects that use wave-adding synthesis (and LFO):

Before going any further, LFO stands for "low frequency oscillation", and makes a particular parameter of some effect oscillate up and down in simple armonic motion. Clear? :) Well, now on to the effects:

Phaser: or "phase shifting" effect, is actually one of the most complex. The concept of "phasing" deals directly with the physical concept of "wave phase". The phaser takes the input signal and produces in it a "phase lag" or offset, retards the wave in terms of the wave phase rather than in terms of time. Another particularity of a phaser is that the phase lag is not constant, it varies with frequency. Normally, the higher the frequency, the higher the phase lag, but the graphic looks logarithmic. The wave amplitude is not modified, however. The sound it produces is similar to that produced when opening and closing the mouth when toothbrushing :). All mathematical.. but when you use a phaser you dont specify degrees for the phase lag or anything like it, you get to play with its LFO parameters, speed or rate for example. There are even "phaser colors"!, but I dont know how the work, basically, they produce different equalizations and richness of sound.

Chorus: basically, the original signal is duplicated, this new signal gets delayed about 20 to 30 ms and slightly detuned, by lowering its playback speed (like slightly reducing the speed of a turntable), and both the processed and the original signals are mixed together. Used a lot on clean tone guitars, to liven up the sound.

Flanger: is similar to chorus: the signal gets duplicated, the new signal gets delayed too, but in varied lenghts, nevertheless, the delay time is not that large to produce echo. Humans perceive echo when the repetitions occur from about 50 to 70 ms, and the delay time of the flanging effect ranges from 1 to 10 ms. The result is kind of a "whoosheew" sound (the famous "plane" effect). The "whoosh-" part is given when the delay time decreases, and the "-sheew" part occurs when the delay time increases. This effect is so distinctive that if used too much it becomes annoying.

Effects based on "Repetitions":

Delay: It consists basically in playing the original audio signal and repeating it after some "delay time". This delay time can be given in terms of milliseconds (or seconds, but not so used) OR BETTER in terms of beats from a determined measure given the tempo. What does it mean? that you can set the delay time so that the repetitions occur, let's say, after an eight note's duration. It's posible due to some formula applied to the tempo obviously. There's another parameter it receaves, called Feedback (or regeneration of sound) which allows to re-send the produced signal, to have several repetitions. Well enough Bullshit.

Delay is, without any doubts, my favorite effect. I love ambiance, and delay provides a lot of it. Reverb is always needed too, but delay helps plain sounds sound much more like a pad, like a musical texture. Also, you can mix the delayed copies of the sound to produce an exact repetition of the original sound, with the same volume and stuff, so, if you move in a scale, you can get something interesting.. :) Used a lot on voices too, because of what I said before, in terms of images, it helps "blur" a little the sound.

Reverberation: There's not only one path from the sound source to your ears. The sound source produces wave omnidirectionally so, some ways travel directly to your ears, while a lot more bounce off of walls before reaching them, faded and retarded because of the energy lost in the bouncing. Reverberation takes repetitions to the extreme, it is different from "echo" and "delay" because of 2 factors: repetitions dont decay or occur proportionally, and those repetitions occur so fast that you actually dont recognize them as copies of the original sound.

Distortion: I'll talk some time about this deformation of the wave. :)

Today's totally irrelevant question:

I like to compare a lot the musical mixing process with the creation of images with, let's say, photoshop or the GIMP: Layers, mixed with each other, given some mixing parameters. Also, the final product in image creation is exported to Wave format with a determined lenght (seconds) and quality (for example: 16 bits, 44100 hz, stereo). With images, it happens the same, they're exported in terms of height/width (cms, pixels, points, inches) and quality (32 bit color, 300 dots per inch, CMYK). I guess by now you could be thinking..
-"WAIT! is there a formula to convert sounds to images and viceversa based on their resolution parameters?"
-"Is there a way to express/communicate exactly the same through both a painting and a song?"
-"Could exist any geometrical transformation to convert a sound sample to an image's pixel?"
-"Can we get to a formula to convert sound waves to light waves?"
-"Can I write myself 5000 pages about my own philosophical model that explains onthologically/episthemologically the world and life through the relation sounds-images?"
-"In terms of Foucault (or Deleuze, name it), can I get lost in a "musical" device after traveling through an "optical perception's device" 's escape path?"

Or perhaps you didnt. Or you're wishing you never read that.

Hernán [12:39 AM] -

the hatemachine,
according to svigle