Acoustic Treatment at San Stefano Plaza

Project Overview

DECIBEL was invited to deliver acoustic and soundproofing solutions for San Stefano Plaza, a high-end multifunctional complex in Sofia. The first request involved the fitness center, where disturbing noise from the ventilation system was affecting the experience of visitors. Shortly after, we were asked to solve another problem. This time related to unwanted noise in one of the building’s rental apartments.

In both cases, the goal was to identify the exact source of the noise and provide a durable and discreet solution that would not interfere with the building’s systems or interior design.

Why Acoustic Treatment Matters

In modern residential buildings, hidden technical installations often generate noise that affects daily life. Vibrations from HVAC systems, water pipes, and mechanical equipment can travel through structures and reach living and working spaces.

When not properly controlled, low-frequency noise becomes stressful and tiring, especially in places designed for rest, exercise, or sleep. Acoustic treatment helps reduce these disturbances and protect the comfort and health of occupants.

Challenge

In the fitness center, the problem was a constant low-frequency humming sound. After inspecting the space, DECIBEL’s engineers discovered that the building’s main air vent passed through the gym. Behind the walls, we also found large parts of the heating and ventilation system. At a 90-degree turn in the ductwork, the airflow produced noise at over 50 Hz, which was audible throughout the space.

In the rental apartment, guests had reported disturbing noise that seemed to occur repeatedly. After detailed acoustic analysis, we traced the problem to the motor-driven circulation of the heating system’s water pipes. The vibrations transferred through the building’s structure and disrupted the quiet atmosphere expected in a luxury rental.

Scope of Work

• Full acoustic analysis and noise source detection
• Custom design of noise reduction systems for HVAC and water pipe infrastructure
• Engineering and delivery of tailored soundproofing materials
• Installation in both the fitness center and the rental apartment
• Post-installation sound measurements to confirm results

Solution

For the fitness center, DECIBEL designed a non-standard treatment for the duct corner. Instead of the typical solution using perforated metal and mineral wool, which can reduce system efficiency, we applied a hybrid solution using both reflective and absorbent materials. This kept airflow performance intact while eliminating the noise.

For the rental apartment, our team developed a custom insulation system using Fomex material and additional layers to isolate the motor noise from the water pipes. We managed the full process, from design to installation, and made sure the system fit within the building’s structure without disturbing its aesthetics.

Result

In the gym, the low-frequency 50 Hz noise was eliminated. Visitors can now exercise in a quiet and comfortable environment. In the rental apartment, our solution brought measurable sound reduction. After the success of the first installation, San Stefano’s team requested treatment for two more apartments.

The results proved that detailed diagnosis, precise design, and high-quality materials lead to effective and lasting acoustic solutions.

Ready to Eliminate Hidden Noise in Your Building?

DECIBEL provides tailored soundproofing and acoustic solutions for complex architectural and technical challenges. Contact us or explore our full range to start your project today.