The stringent acoustical requirements imposed by the Belgian standard for dwellings present a major challenge for architects. In particular the standard defines strict requirements for the global sound insulation between rooms, which is mainly determined by the direct transmission and flanking transmissions in which sound waves produced in one of the rooms excite the flanking structure and generate strucutrla waves, which are transmitted through the structure.
Architects and acoustic consultants struggle to accurately estimate the vibration reduction index for their building designs. ISO 10848 defines a method for measuring this, but it is a long, tedious and expensive process which is implemented by building two rooms and their junctions one by one, exciting the wall and measuring the flanking and direct noise. This process must be done for each building design. When the design changes or the desired results are not achieved, the structure must be demolished and built again from the beginning.
To avoid this costly physical testing process, architects used to use empirical formulas to determine the vibration and noise. However, when the Belgian Building Research Institute (BBRI) measured vibration reduction index for approximately 185 different junctions and compared the results to those empirical prediction formulas, they saw that discrepancies occurred. They created a different formula that they believed was going to be much more accurate, but they had to test it in a wide range of wall properties in order to validate it. They did not have the money nor the time to do this. Eventuallly, they decided to use acoustic simulation software to study flanking noise and direct noise that transmits to adjacent room. “We used acoustic simulation to simulate in-line and corner transmission because of its proven ability to provide accurate results over a broad application range and because it is so easy to use,” said Charlotte Crispin, head of laboratory for BBRI.
Acoustic simulation was used in many different models and the results were accurate every time. More then 900 computations were launched successfully. Eventually, they were able to save significant cost and time. With acoustic simulation, it is now possible to accurately predict noise level and easily comply with the government regulations.