AURUBIS - ACOUSTICS AND SOUND INSULATION OF A MULTIMEDIA EVENT SPACE
Towards the end of last year, we were invited to join a large team of specialists tasked with creating a new multimedia event space for the offices of Aurubis Bulgaria. Designed by architectural studio Style & Practice, the space was developed as an interior extension within a newly created wing surrounding the company’s existing corporate facilities in Sofia. The audio-visual concept was developed by our colleagues at Sound Mind, represented by Andrey Andreev, while we were responsible for the architectural acoustics and sound insulation design of the auditorium.
Our work on the project began with a detailed review of the requirements for the space, the proposed architectural solutions, the materials specified for the interior, and the layout of the auditorium and the surrounding areas. This was followed by a sound insulation analysis of the separating structures. For a more in-depth assessment, we also developed an equivalent 3D model of the space, incorporating all interior surfaces together with their sound absorption and diffusion characteristics. This allowed us to carry out wave-based simulations and detailed modelling of the acoustic sound field well before the auditorium was built, as well as to accurately define its acoustic performance indicators.
One of the first requirements was to ensure that the auditorium would not compromise the comfort of the working acoustic environment in the surrounding office spaces. This was partly addressed at the architectural planning stage through a series of buffer corridors, foyers and technical spaces between the auditorium and the working areas, acting as barriers / sound locks to direct sound transmission. The only direct airborne sound transmission path between the auditorium and the office spaces was through a large separating wall directly behind the stage. For the purposes of the project, this was constructed as a high-performance massive double-leaf structure, designed to provide the required sound insulation across the full frequency range and to accommodate the expected operating levels and excitation spectrum.
Following the construction of the main separating structures, we carried out initial acoustic measurements and used the real-world results to calibrate the model. This allowed us to compare the predicted and measured behaviour of the space in terms of parameters such as reflections, reverberation and sound-field clarity, and to define the necessary adjustments before finalising the acoustic treatment. The most significant issues confirmed by the analysis were excessive and uneven reverberation, pronounced flutter-echo reflections between the side walls, clearly audible reflections from the rear wall, reduced speech articulation and clarity, and resonances in the low-to-mid frequency range.
A significant part of these problems was caused by — and the solutions were made considerably more challenging by — the presence of large floor-to-ceiling glazed façades surrounding the auditorium. They provided generous amounts of natural daylight and attractive panoramic views, but at the same time severely limited the possibilities for acoustic treatment, while their primary architectural function had to remain unaffected.
The acoustic solutions we could propose, not only for this particular issue but for the space as a whole, were further constrained by the requirement to respect the proposed interior design and architectural language, without disrupting the identity and rhythm of the auditorium. This placed significant limitations on both the selection and placement of the acoustic treatments, which had to be integrated into the architecture without compromising its character.
To achieve a balanced reverberation response across the frequency spectrum and reduce the initial time of almost 3 seconds to the required 0.5–0.6 seconds, we developed a system of acoustic solutions combining the necessary performance with a contemporary appearance and a high degree of visual continuity with the corporate interior. With an area of approximately 360 m² and a volume of around 1,330 m³, this required a substantial amount of absorptive surface area to be integrated into the architecture.
We installed wooden absorbers with a perforated slatted surface throughout the interior walls and columns. These were designed to absorb the target frequency spectrum while maintaining controlled scattering of the remaining acoustic energy. All glazed surfaces were treated with double-layer transparent micro-perforated absorbers, allowing daylight to pass through unobstructed while simultaneously absorbing unwanted echo impulses and flutter reflections. The ceiling was optimised by retaining the acoustic panels and baffles proposed as part of the interior design, while integrating the additional mid- and low-frequency absorption required for the space in the form of angular soffit bass traps, which also provided a concealed route for cabling.
The final result is an auditorium in which the acoustic treatment remains a natural part of the architecture rather than an element added to it. The required absorption, control of reflections and sound insulation are integrated into the established interior concept without compromising its primary functions — natural daylight, panoramic views and the visual identity of the space.
