An acoustic challenge in the heart of a listed heritage site
- Project background and objectives
- Technical and heritage constraints
- Acoustic study and methodology
- The Groupe BOËT solution
- Acoustic results and benefits
- In conclusion
Project background and objectives
The main challenge was to reduce an excessively high reverberation time, which was detrimental to the clarity of speeches and the sound quality of celebrations. The aim was to improvespeech intelligibility and acoustic comfort without altering the cachet of the venue.
The building, listed for its historical and architectural interest, imposed strict aesthetic constraints. Any intervention had to integrate harmoniously with the existing structure, preserving the original materials and volumes while providing a measurable acoustic improvement.
Technical and heritage constraints
A highly reverberant environment
The chapel, with its high vaulted ceiling and entirely clad in reflective materials (stone, marble, stained glass), had a reverberation time of over 4 seconds in the 500 Hz frequency band – well above the recommended values for a place of worship, which are between 1.5 and 2.0 seconds.
Preserving heritage character
Interventions had to respect the building’s heritage character. No element could mask or distort the sculpted decorations, stained-glass windows or period ornaments. The Groupe BOËT therefore opted for a discreet, integrated and reversible approach, in line with the expectations of the heritage architects and the site management.
Acoustic study and methodology
Prior to any intervention, a complete acoustic study was carried out by Groupe BOËT teams. This phase included :
- Precise characterization of reverberation time using in situ measurements in accordance with NF EN ISO 3382 ;
- A complete geometric survey of the chapel using a 3D scanner and a geometric survey;
- Numerical acoustic simulations using 3D modeling tools to assess the impact of future treatments;
- Additional vibration analysis to avoid any interaction with existing structural elements.
This approach made it possible to precisely size the absorbent surfaces required and select the materials best suited to the volume configuration.
The Groupe BOËT solution
Groupe BOËT designed and manufactured custom acoustic panels, specifically adapted to the geometry and aesthetics of the chapel. These elements were integrated with particular attention paid to their visual discretion and acoustic efficiency.
Made-to-measure absorbent panels
The absorbent panels are made of high-density mineral materials encapsulated in a microperforated acoustic fabric, colored to match existing shades. Their modular design meant that they could be installed without altering the original walls, in compliance with DRAC recommendations.
Careful installation and heritage coordination
The work was carried out in close collaboration with the site’s technical services and heritage architects. Installation took place without interrupting liturgical activities, thanks to precise phasing and interventions outside service hours.
Performance and integration
Acoustic panels were distributed over strategic areas of reflection (side vaults, rear walls, upper walls), guaranteeing an even reduction in reverberation time while maintaining the sound quality of vocals and instrumental music.
Acoustic results and benefits
Reception measurements confirmed a reduction in reverberation time of over 40% in the mid- and high-frequency bands. The average reverberation time is now in line with recommendations for religious buildings, ensuring :
- Significantly improved speech intelligibility;
- Enhanced hearing comfort for worshippers and celebrants ;
- Consistent sound quality throughout the chapel.
The final acoustic result corresponds to the initial study forecasts, and has been validated by the acousticians commissioned for site acceptance.
Visually, the treatments blend perfectly into the décor, preserving the site’s heritage aesthetic. The chapel retains all its beauty and natural resonance, now balanced and controlled.
In conclusion
With this project, Groupe BOËT demonstrated its ability to work in buildings with a high heritage value, while offering high-performance, sustainable acoustic solutions. Our combined expertise in acoustic studies, custom design and architectural integration enabled us to transform the chapel of the Institut Catholique de Lille into a space that is both faithful to its history and perfectly suited to its contemporary uses.
Would you like to improve the acoustics of a sensitive or heritage building?
Contact Groupe BOËT for a personalized acoustic study and discover our noise treatment solutions that respect both aesthetic and regulatory requirements.
