[NLP]

Jeste!!!
Mnogo puta smo ovdje propovjedali kao "crnu magiju" protiv jednakomjerne perforacije ili sličnih ponavljajučih se uzoraka na površinama studija...
Suvremena akustika se bori protiv takvih starih veoma prostih metoda jer taj način stvara koloracije u prostoru, sasvim se mogu nazvati i aliasing efekt (laže primečivano kod videa) jer je dosta težko dočarati kako je to kod zvuka a još teže kad neko neče da to razumije!!!

Ajde ka poanti...
Možeš da nađeš u literaturi i pod rečenicom "periodicity effects".
Nešto malo o tome (knjiga: Acoustic Absorbers and Diffusers Theory, design and application Second edition):

9.5 The curse of periodicity and modulation
The scattered polar responses seen in Figure 9.6 are dominated by grating lobes generated by the fact that the diffusers are periodic. The lobe energy may be constant, but there are large minima between the lobes except at high frequencies when the number of lobes becomes very large. The scattered energy is not even in all directions. For this reason, significantly better performance can be obtained if the periodicity lobes can be removed by making the diffuser aperiodic or increasing the repeat
distance. The small number of studies on the subjective effects of periodicity have all found that periodicity can cause audible coloration.14 A phase grating diffuser which exploits number theory, such as a QRD, is in many ways cursed by periodicity. A QRD needs periodicity to form its even energy lobes, yet the periodicity lobes cause uneven scattering.
One possibility is to use a number sequence with good aperiodic autocorrelation properties. This means that a single period of the number sequence can be generated and used without repetition. There are two problems with this solution: first there are not many large aperiodic, polyphase sequences known, and second it will usually be cheaper to manufacture a small number of base shapes and use each of these many
times. Angus15–20 presented a series of papers outlining methods for using two phase grating base shapes in a modulation scheme to deal with the problems of periodicity. Figure 9.16 shows such an arrangement for two QRDs, one based on N = 7, the other on N = 5. The idea is to use two or more base shapes and arrange them according to a pseudorandom sequence so there is no repetition. As discussed previously, the far field scattering distribution is roughly given by the Fourier transform of the surface reflection coefficients. For a periodic device, the distribution of reflection coefficients can be expressed as the reflection coefficients over one period, convolved with a series of delta functions: (9.21) where R1(x) is the distribution of reflection coefficients over one period; n is an integer;
* denotes convolution; W = Nw is the width of one period of the device, and δ the delta function.
Equation 9.21 and the following process are illustrated in Figure 9.17. When a Fourier transform is applied to Equation 9.21 to obtain the scattering in [sin(θ) + sin(ψ)] space, then the convolution becomes multiplication: (9.22) where FT denotes Fourier transform. The Fourier transform of a delta function series, is another delta function series and it is the spikes in this for [sin(θ) + sin(ψ)]> 0 that cause the grating lobes. Consequently, rather than use a delta function series to form a periodic device, another function should be used which has better Fourier transform properties. Again, what is needed is a sequence with good autocorrelation properties. A good choice is a Barker sequence. This is a binary sequence whose aperiodic Fourier transform is flattest possible for a binary sequence. Consequently, the response of the whole array of diffusers is closer to the single diffuser alone than if a periodic arrangement is used. If a perfect binary sequence could be found then the single diffuser response would be recovered, but there are no such 1D sequences.

Samo toliko da se nanjuši o čemu je reč.

Ovaj tekst govori o "dosta" kompleksnim! difuzorima (PN 7 i slično) koji se "previše puta ponavljaju" na površinama studija a što tek da je riječ o sasvim prostoj perforaciji i slično???!!!

Više puta su neki "stručni znalci" ovdje na forumu govorili da vidimo fatamorganu odnosno nisu ni znali da to postoji!!!
... znači ima MLS, Barker i slične metode da se periodičan efekat "umiri"... ali treba je imati u obziru da je taj efekat previše puta!!! i posve!!! nezaželjen u prostorijama za kritičko slušanje!!!
... a kad ide za takve veoma!!! preproste periodične uzorke kao periodična perforacija i slično (gde su ček i dosta komplikovani difuzori niskog reda od PN7...), treba je još hitnije!!! malo uključiti maštu i izbječi to!!!