MSC Software Corporation, a global leader in helping product manufacturers to advance their engineering methods with simulation software and services, today announced that The Belgian Building Research Institute (BBRI) used Actran acoustic simulation software (developed by FFT, an MSC Software Company) to validate the accuracy of a new acoustic prediction formula that will help architects comply with stricter acoustic requirements for dwellings.
“We used Actran to simulate in-line and corner structural waves transmission because of Actran’s 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. The results showed that the new formula more accurately predicts the vibration reduction index Kij that determines the flanking sound reduction between two adjacent rooms for in-line and corner transmission in T-junctions, X-junctions and H-junctions.
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 structural waves which are transmitted through the structure. The flanking wall then radiates the sound in the adjoining room.
ISO 10848 defines a method for measuring Kij with physical testing; however, this is a long, tedious and expensive process. Because of the high cost and time involved in physical measurements, architects and acoustic consultants normally use empirical formulas set out in the EN 12354 standard in the design of new buildings. BBRI researchers, within a research activity supported by the Belgian Federal Government (NBN), measured Kij for approximately 185 different junctions and found that the EN 12354 standard prediction formulas left much to be desired. The researchers proposed a new formula based on the characteristic moment-impedances of the junction walls as opposed to the old formula which is based on the mass per unit area of the walls.
The researchers needed to accurately simulate structure-borne sound transmission over a wide range of wall properties in order to validate the new formula. BBRI researchers first used Actran to simulate a typical test setup and found that Actran’s predictions correlated well with physical measurements. After proving the accuracy of Actran’s results, BBRI researchers used the software for a parametric study of a T-Junction, X-junction and H-junction. The researchers evaluated the old and new formulas over 200 different junction designs and found that the new formula provides considerably higher accuracy than the old formula.