The Congregação Cristã no Brasil church, headquartered in the city of Sorocaba/SP, had serious sound quality problems since it was founded in the 1980s. Its architecture with a curved ceiling and practically no absorbent material meant that reverberation was extremely high, reducing speech intelligibility and the clarity of music. To carry out the acoustic project, measurements were taken using the interrupted noise method (ISO 3382 - 1) as shown in video 1.
Video 1 - Acoustic measurements taken for the acoustic project.
Measurements revealed a serious acoustic problem in the church. The TR of the church was close to 5.5 seconds at a frequency of 500 Hz. The optimum TR for this environment, according to NBR 12179, would be around 1.65 seconds. A mathematical model was used to come up with the solution of replacing the plaster ceiling with a hybrid ceiling, consisting partly of a micro-perforated metal ceiling (Garbe Metalfort) and a plant fiber ceiling (Garbe Forrofort), as shown in Figure 1. An additional lining was also specified in the ceiling to adjust the TR in the nave of the church.
Figure 1 - Plaster ceiling (before) and acoustic ceiling (after).
Figure 2 shows the reverberation time (TR) graph before and after the acoustic project as well as the result estimated by the mathematical model.
Figure 2 - Comparison between TR before, after and estimated.
These results were corrected for an occupancy of 30% in the environment. As can be seen, the results obtained were very close to those estimated above a frequency of 250 Hz. Below 250 Hz there was a distortion in the results, but even so the result obtained exceeded the design expectations. Video 2 clearly shows the reduction in TR when compared to the church before the acoustic project was carried out.
Video 2 - Acoustic measurements taken after the acoustic project.
Another desirable result in churches is high speech intelligibility (SI). An environment with intelligibility above 75% is considered excellent. The IF result obtained for this environment can be seen in Figure 3.
Figure 3 - Comparison between before, after and estimated FI.
As can be seen in Figure 3, the IF obtained was above 80%, exceeding the design expectations.
#Cacoustic conditioning #T Acoustic treatment #I Speech intelligibility #Auralization #NBR12179 #ISO3382 1TP5Churches #CCB