In tropical countries, air conditioning systems are widely used to improve indoor climate. In many cases, natural ventilation can also provide thermal comfort for users with less energy consumption and better air quality as long as the pollution outdoors is not too high. However, openings in the facades for natural ventilation decrease the sound insulation. Consequently, it is important to evaluate different facade designs in order to minimize the sound transmission through possible ventilation openings (VO). 

This work is aimed to analyze acoustics performance of VO patterns and give suggestions for optimizing facades. For this purpose, the sound transmission loss (TL) of five VO bricks were simulated using Boundary Element Method (BEM) and COMSOL. Beside the single opening, several opening patterns (e.g., four VOs in square and in a row) were investigated. Then, a laboratory measurement was conducted for three of the small-scale patterns, to compare with the simulation results. 

As the simulation result, the opening area has a great impact on the TL especially at low frequencies. Notably, the VO avoiding direct sound has a highest TL overall. Sound incidence angles not orthogonal to the wall improve the TL significantly. There was only subtle difference between each pattern with the same opening area. From the measurement result, the sound reduction index can be observed to show an agreement with the simulation partially. 

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