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PERCEPTUAL INTEGRATION
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wayak
IsraTrance Junior Member
Started Topics :
10
Posts :
51
Posted : Apr 20, 2011 19:21:32
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I JUST FINNISHED READING AN ARTICLE THAT I THINK IS OF GREAT INTEREST FOR EVERYONE IN THIS FORUM, I SUGEST FOR BEGINNERS THAT IF YOU DONT UNDERSTAND MOST OF IT NOW OR DONT KNOW HOW TO APPLY IT IN YOUR MUSIC AT THE MOMENT, TO COME BACK AND READ THE ARTICLE BECAUSE EVENTUALLY YOULL FIND THIS VERY VERY USEFULL.
you can read the fist part of the article in this link www.soundonsound.com/sos/apr11/articles/perception.htmand , ill write the rest of the most important things here (SHHIIT!!! jaja but its worth the effort).
continuation on the article....
In audio production there are lots of situations where you can take advantage of this merging. A good example would be attack replacement: cut the attack from a snare drum and put it at the beginning of a cymbal sample. The two sound will be perceptually merged and you will get a nice hybrid.(audio examples from 16 to 18, also on the link i gave you) this is but an example and many other aplications of this simle phenomenon can be imagined.
CREATING PITCH
With sound impulses one second apart we hear a series of impulses. However reducing the time between the impulses brings a truly spectacular change of perception: at around a 50ms spacing, we pass the upper threshold and begin to hear granular pitched sound, as we near 10ms and cross the lower threshold we begin to hear a smooth pitched wave form and its quite hard to remember that what your hearing is a sequence of impulses. (audio examples 19 to 33) to witness this phenomenon.
This points to a fundamental property of hearing: without perceptual time integration we would have nosense of pitch (very important fact).
Its no coincidence that the lowest pitch we can hear 20hz corresponds to a period of 50ms.
below 20 hz we can indeed hear whats going on but we do not percieve it as pitch... we hear clocks ticking even though they tick at 1hz, we just cant derive pitch from ticking.
In audio production reducing the interval between consecutive samples to below perceotual time thresholds can be of real interest. A good example found in grantz graf by autechre between 0.56 and 1.05 you can witness a spectacular example of a snare drum being turned into pitch then back into another loop.
the same phenomenon can be used in psytrancefor example you can make a transition between to parts of the track based on the removal of the kick and harmonic layer with parts of the lead being locally looped near the integration zone.
AM SYNTHESIS: TREMOLO BECOMES TIMBRE
the idea that simply changing the amplitude level of sound could alter its timbre is odd, but can be achieved with Amplitude modulation (AM) made by bob moog as a way to create sounds. Its an audio synthesis method that relies on the ears integration time.
When levels change at a rate that aproaches the ears time thresholds they are no longer perceived as tremolo but as adding harmonics which enrich the original waveform (ver very usefull for psy when combined with a note to freq chart, and the use of root notes 3rds fifths,etc, yeahh!!).
AM synthesis uses two waveforms the first one called carrier, and level changes are applied to this in a way that is governed by a second waveform, Bla bla bla, if you dont know AM look it up... ill continue on...when we modulate the carrier with a sine wave that has a period of one second, the timbre of the carrier appears unchanged, but we hear it fading in and out. When it wets closer to 50ms(upperthreshold of perceptual integration) level changes are not perceived as much anymore. instead it now exhibits a complex granular aspect. as the lower threshold is aproaxed, from 15ms downword, the granullar aspects dissappear and the carrier is apparently replaced by a completely different sound. audio examples 34 - 48 (in the link) hear the transition from level modulation through granular effects to timbre change.
In audio production, we can apply these principles to create interesting sounding samples with a real economy of means.
an example would be asigning lfo to the amplitude of a sample, going below the integration threshold.
this can be done with numerous tools, pure data, max msp, reaktor, arturia arp 2600, or with amplitude automation in your daw.(remember going below 50ms and experimenting, i can think of the use of note to freq chart, from C0-16.35hz to G1-49.00 
FM SYNTHESIS: VIBRATO BECOMES TIMBRE
ok i wont write what fm is jajaj look it up if you dont know what it is but heres the rest... the diference between am and fm is that one affects amplitude and the other frequency.
when a carrier is modulated by fm synthesis whose period is one sec: we hear changes in pitch or vibrato, but if we reduce the period to 50ms we begin to have trouble hearing pitch changes and experience a strange granular sound. Near 10 ms the result loses its granularity and a new timbre is created. audio examples( 49 to 63...from freq modulation to timbre change) we can do this in a synth assigning lfo to pitch and going below 50 ms.
PANNING, DELAY & STEREO WIDTH
a well known trick that takes advantage of integration time is the use of delay to create the impresion of stereo width. take a mono file and put it on two distinct tracks pan the first hard left and second hard right, delay one of the tracks one second, we clearly hear two ocurrances of the same sample, if we reduce to 50ms the two ocurrances are merged and we hear only one sample across the stereo field, going downwards this width impression remains untill 20 ms, after whitch the stereo image gets narrower and narrower, aduio examples 64 to 78.
DELAY BECOMES COMB FILTERING
take a mono file, put it on two tracks and delay one of the tracks, but this time dont pan anything to the right or left. If we set the delay at one second we heard the same sample twice. as we reduce the delay to 15 ms or so (the lower threshold of perceptual integration, in this case) the delay dissapears and is replaced by a comb filter. This works even better whith multitap delays.
With a delay value set at 1 s we hear the oroginal sample superimposed with itself over and over again. At a delay value approaching 40-50ms (upper threshold in this case) we still can hear the difference delay occurrences, but the overall effects is of some kind of reverb that recalls an untreated corridor.
Getting nearer 10 ms the lower threshold in this case we only hear comb filter. 80 to 94 to listen the transition between multitap, weird reverb and finally comb filter. GRM comb filter for this purposes, experiment going near the integration zone!
like wise very short reverbs are not heard as reverb but as filter. filters can be thought of in some ways as extremely short reverbs...
subject discused in detail in this link( www.soundonsound.com/sos/sep10/articles/convolution.htm
DYNAMICS & DISTORTION
dynamic compression involves levelling signal amplitude: any part of the signal that goes over a given level threshold will be attenuated.
Consider a signal thats fed into a compressor. suddently a peak appears thats above the level threshold: compression kicks in and negative gain is applied instantaneously. If it was, the signal would simply be clipped, generating harmonic distortion. this can be interesting in certain cases, but the basic purpose of compression remains compression, not distortion. As a consecuence, gain reduction has to be applied gradually. The amount of reduction should be 0db at the moment the signal goes over the threshold, and then reach its full value after a small amount of time; the attack time setting in a compressor determines exactly how much time.
Of course there is much more to dynamic compression than the attack time, other factors shuch as the shape of the attack envelope, the relese time, and the relese envelope shape, all have potential to affect our perception of the source sound in music production, compressors are often set up with time constants that fall below the threshold of perseptual integration, and this is why we think compressors having a sound of their own.
A STARTING POINT
this article covers many situations in which perceptual time integration can bring unexpected and spectacular results from basic modifications of the audio signal.
Think about it: since when are simple level changes supposed to add harmonics to a sample? (AM)
how on earth can a simple delay actually be a comb filter?
There are many other examples that this article doesnt cover. for example what happens if you automate the center freq of a shelf eq to make it move very quickly, or automate panning at very high freq that freq match your root note freq etc.
OK FINALLY IM DONE HAHAH HOPE YOU TAKE ADVANTAGE OF THIS VERY USEFULL ARTICLE, THE MORE CONTROL WE HAVE OVER OUR SOUND THE BETTER.
LEAVE YOUR IDEAS ON THIS MATTER!!
WAYAK
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wayak
IsraTrance Junior Member
Started Topics :
10
Posts :
51
Posted : Apr 20, 2011 19:24
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PsyGalaXy
IsraTrance Full Member
Started Topics :
68
Posts :
437
Posted : Apr 21, 2011 19:18
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SpEeD
IsraTrance Junior Member
Started Topics :
29
Posts :
27
Posted : Apr 21, 2011 23:38
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Very nice article men, I´ve read it all and it shows some very interesting aspects in music preception. Thanks! |
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wayak
IsraTrance Junior Member
Started Topics :
10
Posts :
51
Posted : Apr 22, 2011 00:41
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yup.. very interesting, they really know their stuff at SOS |
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