Mannis' project meant his doctoral thesis, defended on the 22nd, under the guidance of professor Jonatas Manzolli. Therefore, it brings many theoretical foundations of music, in addition to a broad review of the literature related to the research – such as acoustic principles, typology of symmetries, elements of serial composition that inspired the new diffusers and acoustic evaluation criteria.
The research began 11 years ago, when the author was invited to complete the finishing work at the Musical Acoustics and Information Technology Laboratory (Lami) at USP. “We have Schroeder diffusers on the market, which spread sound well, but produce absorption. The sound wave loses energy when it hits the diffusing surface, with an attenuation of up to five decibels. As they did not serve my purpose, the challenge of the research was to achieve diffusion without loss”.
To the layman, José Augusto Mannis explains that an essential criterion for the musician is reverberation – the sound that spreads throughout the space. “The flutist who blows a note considers that sound that is in the reverberation halo as 'his'. This way, he can resume the music between one breath and the next. The specific terminology for this musical parameter has been translated in Brazil as 'sound filling'”.
By the way, Mannis recalls the observations of composer and conductor Daniel Pinkham about Bach's organ compositions, which in each era change style depending on the acoustics of the place. At first, Bach performed at the St. Jacobi Kirche, in Luebeck, and then at the Thomaskirche, in Leipzig, the latter with drier acoustics.
The author of the thesis explains that, in large rooms, or rooms with greater reverberation, the tendency for fewer events leads to slower execution. “This is because reverberation, even though it is beneficial, contributes too much to the confusion of notes. The musician shapes the way he plays depending on the acoustic response of the room. The only instrument that does not require this criterion is the piano, which has a resonance pedal.”
Diffusion and absorption – The sound is filled by the reverberation that occurs in a diffuse field. Diffusion can be produced with irregular obstacles in the path of the sound waves, as is the case with diffusing surfaces. “A kind of controlled chaos is caused. On the smooth surface of a table, sound hits and exits at the same angle. But if it hits an irregular stone, the sound hits and opens like a bouquet, spreading in all directions.”
Another example from Mannis is a square room, which due to this geometry is subject to standing waves located in coincident regions and points. “When listening to music indoors, anyone who sits in these places will be at a disadvantage. But if there is a good diffuser panel on the walls or ceiling, it will spread the waves in all directions, comprehensively and evenly.”
The loss of energy, however, is a deficiency that Schroeder diffusers have not been able to overcome. According to the author, the loss arises from eddies between low and high pressure zones located at the entrance to the diffusers. “Particles always try to get into the easiest place.”
Still on this aspect, the professor uses the image of people who, faced with a full elevator, run to the next elevator, and return to the first one when the second one is full. “Part of the energy is spent not on going up and down, but on moving from one elevator to another. What I did was move the elevators further apart, avoiding this rush.”
Thus, Mannis designed diffuser surfaces with smooth articulations, some more linear, others more rounded, and also those in which each element can be rotated back and forth.
“The solutions I propose do not have abrupt articulations and one element is always different from the other. Therefore, there is no loss of energy but rather the scattering of sound waves. The important thing is the design, regardless of the material used (wood, plaster, plastic), which also allows cost control”, he observes.
Contemplation – José Augusto Mannis states that he found most of the solutions intuitively and that the review of acoustic principles, as well as the resumption of physics concepts and mathematical calculations were necessary to detail, in academic language, the design of diffusers that wove in thought.
“Since I started working with electroacoustic performance, when I was a student, before preparing a device project for a concert, I started sitting in the room looking at the walls, the ceiling, the objects, imagining what it sounded like. And in that game I put the speakers here and there, and tested them mentally”, he recalls.
Thanks to this contemplative stance, the professor was able to observe the association of Schroeder's theory – which is based on a mathematical formula to adjust the depth of the elements of the diffusing surface in relation to the frequency range – with Schoenberg's atonal composition system, of twelve sounds, the twelve-tone series.
“Schroeder diffusers are created from a series of numbers aligned according to complex symmetrical schemes. I say it is a necklace of numbers, as they are not repeated in the structural alignment, and only reappear in symmetrical orders. When the symmetry is more complex, as in a Schroeder diffuser in a fractal scheme, diffusion is better”, informs Mannis.
On the other hand, in Schoenberg's compositional system, each of the twelve sounds is treated as a different element. “I realized that the symmetry scheme resulting from Schroeder's formulas is the same as that in series used in many songs, especially by Webern [an exponent of serialism]. It concludes that part of the procedures for creating a diffuser can generate a series of notes, as idealized by Schoenberg.”
To the wall – Therefore, José Augusto Mannis intuited that the twelve-tone series, with the sounds replaced by numbers, could literally be applied to the wall, aiming to calculate angles, inclinations, widths, thicknesses, heights, diameters and the definition of appropriate materials to reach to an absorption-free diffuser.
The author of the thesis created software that, fed with numbers, drew the shapes of diffusing surfaces on the computer screen, until arriving at the three patented types. The last version, however, was inspired by a truck loaded with pipes, which Mannis could not pass on the road. “I serialized the radius of the pipes and created a semi-cylinder diffuser, where the sound wave undergoes continuously varying deviations, spreading without loss of energy.”
Diffusers attract interest from the cinema segment
Professor José Augusto Mannis has already been receiving invitations from the cinema segment to detail his conception of acoustic improvement, at the same time as he celebrates the good results of the measurements of the three new types of diffusing surfaces, carried out in the Villa-Lobos concert hall, at UniRio (Federal University of the State of Rio de Janeiro).
It was the Unicamp Innovation Agency – Inova, where the patent for the diffusers is deposited, that identified cinemas as potential demanders for the products designed by Mannis, advising him to make commercialization viable. “Inova helped me a lot, as I didn’t even know the broad scope in which I could explore the results of my research”, he praises.
In the researcher's opinion, the market for new diffusers goes beyond that of recording studios and concert halls, and can also present good results for acoustic comfort in classrooms, home theaters and companies. “In some meeting rooms, absorbent material is placed on the walls, which muffles the sound, making it difficult for the person on the other side of the table to be heard.”
In the case of cinema, Mannis explains that the acoustics need to be dry and perfect, with a homogeneous response, which is not always possible due to the architectural design of the room. “A challenge is to design a space where the sound perception is homogeneous and continuous across the speakers. Currently, cinemas pursue the international quality seal, submitting, among other requirements, the evaluation of rooms with precise acoustic measurements”.
SSound wave diffusing surfaces occupy the walls and ceiling of listening and musical performance rooms, such as auditoriums and recording studios, in order to ensure acoustic comfort. José Augusto Mannis, professor at the Institute of Arts (IA) at Unicamp, equipped himself with the knowledge accumulated in music, reviewed engineering subjects studied in ancient times and bet on intuition to develop design solutions that led to three new types of diffusers, with patents already requested. The difference between these diffusers is that they do not present the problem of sound absorption. 
PRESS ROOM - � 1994-2008 State University of Campinas / Press Office