Acoustic treatment with hanging acoustic baffles of the New Bulgarian University, Sofia

Project Overview

Following a successful partnership in 2017, New Bulgarian University once again turned to DECIBEL in early 2019, this time to improve the acoustic comfort in their newly built classroom sector. The challenge was to reduce excessive reverberation caused by the glass-heavy design of the space.

Challenge

The classrooms were constructed entirely from glass partitions that didn’t reach the ceiling, creating an "aquarium" effect. These hard, reflective surfaces increased reverberation time and allowed sound to travel between rooms. The result was poor speech intelligibility, mental fatigue for speakers, and reduced student concentration.

Since the fit-out was already completed, the solution had to be retrofitted with minimal disruption to the existing interior.

Scope of Work

• Acoustic assessment of reverberation time and intelligibility issues

• Acoustic prescription tailored to the glass partition design

• Design and supply of custom baffles made from:

  • Impregnated technical polyurethane

  • Acoustic textile covering

• Horizontal ceiling installation to preserve the room's open visual identity

Solution

To address the echo without altering the transparent architectural aesthetic, DECIBEL installed horizontal acoustic baffles across the open ceilings. These baffles absorb sound reflections while maintaining air circulation and the openness of the space.

Result

Post-installation measurements showed a 4 dB improvement in acoustic comfort—an audible difference. The reverberation time was brought below the regulatory limit of 0.80 seconds for educational spaces. The upgraded classrooms now offer better focus, communication, and learning outcomes for both students and educators.

Glass partitioning is popular in modern educational and office environments, but it often leads to overlooked acoustic issues. Integrating acoustic treatment after construction can increase project costs and complexity. This case illustrates how post-build solutions can still be highly effective when handled by a specialised acoustic team.

Looking to fix acoustic issues in your educational or office space? Contact DECIBEL for tailor-made solutions that respect both form and function.