Anechoic Chambers for Polish National Metrological Office

Project Overview

The Polish National Metrological Office (GUM) commissioned DECIBEL to design and deliver two of the most advanced anechoic chambers in Europe, located in Kielce, Poland. The facility would become a national benchmark for precision sound and vibration measurements, supporting metrological science, industrial testing, and medical device calibration.

Engineering Silence for Science

These chambers are built for scientific precision. In an environment where sound pressure levels fall below human hearing, even a minor vibration or reflection can compromise test accuracy. GUM required chambers that could achieve free-field conditions and comply with ISO 8253-2 standards for audiometric testing.

The project demanded quietness and total control over sound, vibration, and airflow, turning silence into a measurable scientific instrument.

Challenge

The site’s location, just five kilometres from active quarries, presented major challenges. The chambers had to be isolated from both ground vibrations and external noise, meeting Vibration Class V0, the strictest international standard, allowing ground motion below 4 μm/s.

GUM’s requirement also included achieving NR5 internal noise levels, making sure that the rooms would remain acoustically neutral and unaffected by external or structural interference.

Scope of Work

• Design and construction of two anechoic chambers (1402 m³ at 50 Hz and 319 m³ at 100 Hz)
• Implementation of box-in-box reinforced concrete construction
• Design and installation of vibration isolation systems using steel springs and elastomer supports
• Precision installation of polyurethane acoustic wedges (170 cm and 86 cm lengths)
• Integration of a silent ventilation system with 13 m-long ducts and split silencers
• Validation through finite element simulations and on-site vibration testing

Solution

DECIBEL and its partners implemented a box-in-box design, creating two isolated “acoustic islands” inside the building.

The 100 Hz chamber was built on elastomer pads with a 5 Hz natural frequency, while the 50 Hz chamber used 2.5 Hz steel springs, ensuring complete separation from structural vibrations. FEM analysis confirmed full compliance with client specifications, even under real quarry detonation conditions.

Inside the chambers, precision-cut polyether polyurethane wedges were installed with millimetre accuracy to absorb all reflections and maintain free-field acoustic behaviour. For ventilation, custom-engineered ducts with multi-stage silencers ensured airflow without generating audible noise.

Result

The completed facility achieved all design benchmarks, with measured background noise below NR5, vibration isolation exceeding Class V0, and free-field conditions from 50 Hz upwards.

The GUM anechoic chambers now rank among the most advanced acoustic laboratories in Europe, supporting national and international research in audiology, noise measurement, and industrial acoustics.

As DECIBEL’s CEO, Eng. PhD. Tsvetan Nedkov, stated:

“Projects like this prove that silence is not emptiness - it’s precision, innovation, and progress.”

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