Do you have questions ?
In schools, halls, restaurants and hotels there are usually three problems:
Echo is solved with sound absorption – panels on the ceiling and walls. Noise to the neighbours and noise from building services are solved with sound insulation and vibration isolation. Panels do not stop noise to the neighbours: that needs a barrier – a wall, a ceiling, a door.
Ordinance No. RD-02-20-3 of 2015 sets the maximum reverberation time in empty, finished classrooms – averaged over 500, 1000 and 2000 Hz (Art. 102, Table 12):
| Learning space | Max. reverberation time |
|---|---|
| under 283 m³ (standard classroom) | 0,6 s |
| from 283 to 566 m³ | 0,7 s |
| over 566 m³ and auxiliary learning spaces | 0.7–1.1 s (up to 1.5 s) |
Before the building is put into service, the reverberation time is measured (Art. 19(2)). Ordinance No. 6 of 2006 limits intruding noise in a classroom to 40 dB(A). Ordinance No. 4 of 2006 requires sound insulation of Rw ≥ 47 dB for walls between classrooms and to the corridor, and Rw ≥ 55 dB to gyms and music rooms.
What we do:
A hall for speech and a hall for music have different goals. For speech we aim for a short reverberation time and high speech intelligibility (STI). For music – more “life” in the sound, but no echo. For buildings with auditoriums, Ordinance No. RD-02-20-3 requires an acoustic design as part of the architectural design (Art. 218).
What we do:
Examples: EPC Varna, Vazrazhdane community centre.
In a restaurant, noise feeds on itself. When the room echoes, people raise their voices to hear each other, and the room gets even louder. Sound absorption on the ceiling and walls breaks this circle.
Other requirements apply to the neighbours. Under Ordinance No. 4 of 2006, walls and ceilings between a restaurant with levels up to 85 dB(A) and homes must have Rw ≥ 62 dB, and with amplified sound up to 95 dB(A) – Rw ≥ 72 dB. In a hotel, walls between rooms and to the corridor must have Rw ≥ 47 dB. Ceilings and floors between playrooms or other common areas and bedrooms – Rw ≥ 55 dB and L′nw ≤ 46 dB.
What we do:
Examples: the Kalistratov Group restaurant, Grand Hotel Therme, FeelBetter restaurant, the kids’ club at Hotel Lion.
Is reverberation time mandatory in schools?
Yes – for new buildings and when designing a reconstruction, major renovation, major repair or conversion (RD-02-20-3, Art. 1(2) and Art. 102). For a renovation, the design brief may allow a deviation, but only with a technical and economic justification. The result is checked by measurement before the building is put into service (Art. 19(2)).
Will panels stop noise to the neighbours?
No. Panels absorb sound inside the room. Noise to the neighbours is stopped by a barrier – a wall, ceiling, door or window.
Do you issue a commissioning report?
No. Our measurements are an engineering assessment – for diagnosis and design. The official report is issued by an accredited inspection body. We can arrange it.
How many panels are needed?
It depends on the volume, surfaces and use. For the Kalistratov Group restaurant the calculation gave 25–35 m², for the gym in Pirdop – about 90 m².
Submit an inquiry about your issue by contacting us via phone or email. It is recommended to include photos and measurements of the space.
Our engineers visit the site. We get to know the room and how it is used, and propose an approach to the solution.
We measure using the methods of EN ISO 3382 (reverberation, speech intelligibility), EN ISO 16283 (sound insulation) and others – as an engineering assessment. When an accredited test report is needed, we arrange it through an accredited inspection body.
We build a computer model of the room and, when needed, measure the sound absorption of the surfaces on site with the Sonocat intensity probe. We calibrate the model with the measured values and compare options before any materials are bought.
The acoustic panels and screens are made in our own workshop – to size and colour. We deliver and install them with our own team.
When the work is carried out by another contractor, we check the quality of the materials used and that they are installed correctly.
After installation we measure again to check the result achieved – whenever the site allows.
Our engineers visit the site. We get to know the room and how it is used, and propose an approach to the solution.
We build a computer model of the room and, when needed, measure the sound absorption of the surfaces on site with the Sonocat intensity probe. We calibrate the model with the measured values and compare options before any materials are bought.
When the work is carried out by another contractor, we check the quality of the materials used and that they are installed correctly.
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