What do you do when you have a restaurant with a fabulous location and chef but with terrible acoustics? The food may be great but the irritating sound will chase away many of the guests. This was the problem facing the Tatá Restaurant in Rome.
The owner, Sergio had built up a well-respected restaurant in the EUR district of Rome. He had a famous chef from Naples with his own secret recipe for the pizza cooked in the traditional Ciro wood-burning pizza oven. He also specialised in authentic Roman cuisine serving Chianina, a high-quality beef reared on the Tuscan hills (washed down with a good bottle of Gualdo del Re wine).
After talking to his architect, he appointed an acoustic engineer to assess the problem. Having seen the solutions offered at the Palazzo delle Esposizioni in central Rome, they called in Pellisari Consultancy, the consultancy arm of NACSound Srl.
Francesco Pellisari has worked in acoustics and design for many years, even spending some time with Roy Allison (the pioneer of modern speaker design and developer of the first dome silk tweeter). Using his technical instruments and experience, together with his taste for Italian design, Francesco set about understanding the problems that the shape and fabric of the building were creating. He sat and listened, while sampling the fine foods and wine (a difficult job but someone has to do it). He spoke with the staff and his fellow diners to get to the heart of the problems as he considered the possible solutions.
He explained that unwanted resonance was a cause of many of the acoustic problems. (Resonance occurs when sound waves reflect off a surface in phase with another wave so that the two waves are enhanced in wave height). He talked over his conclusions with the restaurant owner and agreed on a plan of action, outlined here below.
The hard reflective original marble surface was replaced by specially designed 30mm thick flooring made of many pieces of compressed wood. Each piece is formed with a small air gap that runs along the edge of the surface. This is filled with an acoustically opaque wax and is excellent for absorbing high frequency sound.
The original plaster covering was very reflective of all wavelengths. This was covered with 30mm of acoustic plaster. This material starts life as a mixture of plaster and polystyrene, which is then chemically removed, leaving an air-filled product that is strong and light with an exceptional ability to absorb medium and high frequencies.
The junction of hard glass windows and walls caused particular problems in one corner, so an ingenious solution was employed. On this wall was mounted a floor to ceiling wine rack. To break up the resonant waves the cubicles were made to different sizes and the wooden sides and shelves were of different depths. The entire structure then acted like a Schroder diffuser.( a Schroder diffuser is named after Schroder who was the first to identify and build a structure to dissipate sound waves)
The false ceiling was fitted. It was made of MDF. To improve its high frequency absorption, perforated slits were cut through to a central hollow space behind in which was placed 100mm Hollowfill.
The restaurant has a very high ceiling and the voices of the guests resonate harshly. To overcome this and to effectively lower the ceiling, large rectangular pieces of ‘kite’, a paper-like material, were suspended from the ceiling. These absorb most frequencies and cut the wavelengths, thereby reducing any harshness and disturbance. Also, by lowering the ceiling the perceived space is more welcoming and intimate.
The central part of the restaurant is small and square with one metal covered wall. It produced a very large resonance at a precise frequency. This phenomenon was first understood by Hermann von Helmholtz in 1890, who then produced a device for measuring it. The frequency was calculated and long, thin light boxes were positioned above the bar to disrupt the wave.
To supply the entire restaurant and the bar zones with stereo sound at a low, yet audible level, two Kayak speakers were chosen. These aluminium omnidirectional stereo speakers were suspended from the ceiling with the computer-designed acoustic wave-guide at head height. This diffused the sound in all directions.Only omnidirectional sound can accommodate rooms with such a high resonance potential, as it is able to deliver four times the power to the listener. It also enhances low frequency sound reproduction at the same time as delivering complete sound saturation of large spaces. Because the sound waves spread out in a spherical pattern they reduce resonance with hard reflective surfaces because when they reflect they do not enhance each. The end result is a more natural sound.
To enable the restaurant to host loud party-type events seven ceramic Zemi speakers were installed: two in the bar zone and five in the restaurant. These multidirectional speakers were suspended three metres from the floor so they concentrate the sound beneath them and limit excess noise disturbing the surroundings – very important for those large family gatherings at Christmas.
The entire system is set up to run off an independent sound source such as a personal MP3 player. This is fed into an Onkyo amplifier and controlled using a Sonance volume controller. This gave six independent channels, each covering a zone in the restaurant and bar, so that the volume in each zone can be controlled independently.