Belgium Parliament

A model of elegance and engineering excellence.

The Chamber of Representatives, located within the neoclassical Palace of the Nation in Brussels, has stood as the heart of Belgian democracy since the eighteenth century. Its architectural and historical significance makes it a space of national importance. However, the very features that give the Chamber its grandeur, its dome, marble surfaces, and ornamental finishes also present serious challenges for speech intelligibility.
In a room where clarity of speech is essential for democratic debate, the acoustic shortcomings of the space had long been a concern. Over the years, various sound reinforcement systems were introduced with limited success. The primary problem persisted: poor intelligibility, especially due to the uncontrolled reflections generated by the overhead dome.

To address these issues, the Belgian government launched a public tender for acoustic solutions aimed at improving speech intelligibility while preserving the building’s historical aesthetics. Amptec was awarded the contract and became responsible for leading the entire process.
Artnovion was brought in to design and supply the acoustic treatment. Their approach started with an extensive evaluation of different treatment options, supported by detailed simulations. The analysis identified a frequency range where intelligibility was most affected. As a result, the final solution combined Helmholtz resonators tuned to those specific frequencies with broadband absorbers to address more general reverberation issues. The goal was to restore speech clarity without compromising the character of the space.

3D Scan
Reverberation measurement

Amptec began by conducting a full technical analysis, including 3D modelling of the space and acoustic simulations. These studies confirmed that the dome was the principal source of reflections disrupting clarity. Reverberation times and STI values highlighted specific problems in the mid to high frequency range.

Adapting without compromise.

The first phase focused on the periphery of the central hall, specifically the balconies.
Given the architectural constraints, standard panel installation was not an option. Artnovion developed a custom solution with a focus on sound absorption. After the installation of the new sound system, part of the treatment was aimed at the 250Hz–500Hz range. Faced with both acoustic and architectural challenges, three different types of semi-curved panels were developed: a broadband absorber, a perforated Helmholtz absorber, and a custom-printed panel replicating the texture of the original marble. Achieving a visual match required a careful process of capturing high-resolution photographs of the curved marble façades, which were tested and refined through multiple iterations across countries to ensure consistent colour matching.

Broadband
absorber
Perforated
Helmholtz absorber

The second phase focused on the centre of the space, where a dome concentrated reflections that, combined with the strategic placement of the loudspeakers, allowed for targeted acoustic intervention. As depicted, domes present a unique acoustic challenge by concentrating sound reflections at specific points rather than dispersing them uniformly. This leads to acoustic hotspots and irregular sound pressure distribution, which can compromise speech clarity and overall sound performance. Covering it entirely was not feasible due to heritage and visual impact concerns, and a simple suspended cloud (although very efficient) would have introduced unnecessary visual noise

This presented an opportunity to create a central chandelier that would also function as an acoustic element. As the lighting system also required replacement with an energy-efficient solution, a concept was developed by Painting with Light in collaboration with the architectural team, and subsequently approved. Artnovion then adapted the design, integrating acoustic materials and conducting simulations to validate the chandelier’s acoustic performance.

From Design to Execution.

During installation, an Artnovion team was present on site to supervise the process and ensure compliance with the acoustic specifications.

The building’s historical significance and its function as a public venue meant that multiple safety regulations had to be observed during the development of the solutions. Fire-rated materials were an essential requirement for this project.

After the complete installation, new acoustic measurements were taken and the true impact was clear. As the graph above illustrates the reverberation time (T60,Sabine) across octave band frequencies before and after the acoustic treatment of the space. Prior to intervention, reverberation times consistently exceeded recommended limits, particularly in the low and mid-frequency ranges, reaching values above 2.0 seconds. This indicated a space with excessive reverberation, compromising both speech intelligibility and acoustic clarity.

Following the implementation of Artnovion’s acoustic solution, measured post-treatment results show a substantial reduction in reverberation time across the entire frequency spectrum (even better than the simulation). Most critically, the measured results fall consistently within the target reverberation zone, defined by the shaded areas in the graph. This not only validates the effectiveness of the acoustic treatment but also highlights the precision of Artnovion’s modelling tools.

This outcome demonstrates Artnovion’s ability to improve complex acoustic environments through a combination of tailored design, technical analysis, and onsite execution. The close alignment between predicted and measured results reinforces the reliability of our approach and our capacity to deliver effective, customised solutions.