Today's urban centers become denser, which contributes to higher demands on sound and noise. It is therefore highly relevant to build homes with good sound environment while maintaining living space. This thesis aimed to reduce the current concrete walls and see how the mass law affects the reduction index value and flanking transmissions. Handmade calculations were calculated according to the Swedish standard SS-EN 21354-1, where only air sound was calculated. Calculations we­­­re performed on wall elements with different weights and thicknesses, and compared with results from Bastian. In Bastian calculations of flanking transmissions were also made, this was made to see the impact of the flanking transmission when changing the mass per unit area. Mass law's impact was examined by flanking transmission and the result shows that they are not affected as long as the ratio between the thickness and the density remains the same. A questionnaire survey was conducted to determine the actual sound experience; this questionnaire was conducted on three concrete buildings in Växjö. Results from hand calculations, Bastian and the questionnaire were analyzed and joined. The mass law affects flanking transmissions very little and therefore a conclusion is drawn that more action is needed and not only improvement of individual elements and how they are connected. Results indicate that today's apartment partitions do well for airborne sound between rooms. In the future this could lead to selection of thinner walls. / Dagens stadskärnor blir tätare och detta bidrar till att högre krav ställs på ljud och buller. Det är därför högaktuellt att bygga bostäder med god ljudmiljö och maximal boyta.  Examensarbetets syfte var att minska dagens lägenhetsavskiljande betongväggar och se hur masslagen påverkar reduktionstalet samt flanktransmissionen. Handberäkningarna är utförda enligt svensk standard SS-EN 21354-1 där enbart luftljud beräknades. Samtliga beräkningar utfördes på väggelement med olika ytvikter och tjocklekar och jämfördes senare med resultat från Bastian. I Bastian beräknades även flanktransmissioner, detta för att se flanktransmissionens inverkan vid ändring av ytvikt. Masslagens inverkan granskades och resultatet visar att flanktransmissionen ej påverkas så länge förhållandet mellan tjockleken och densiteten förblir densamma. En enkätsundersökning utfördes för att bestämma den verkliga ljudupplevelsen, denna undersökning utfördes på tre betonghus i Växjö. Resultat från handberäkningar, Bastian samt enkäten analyserades och sammanställdes. Då masslagen inverkar på flanktransmissionen kan en slutsats dras att det behövs fler åtgärder än enbart förbättring av enskilda element samt hur dessa kopplas ihop. De sammanfogade resultaten pekar på att dagens lägenhetsavskiljande väggar klarar sig bra för luftburet ljud mellan olika lägenheter. Det skulle i framtiden kunna innebära att tunnare väggar väljs, med ökad densitet och bibehållen ljudklass.

Describing planned acoustic design by single number ratings yields a weak link to the subjective event, especially when the single number ratings are interpreted by others than experienced acousticians. When developing infrastructure, tools for decision making needs to address visual and aural perception. Visual perception can be addressed using game engines and this has enabled the establishment of tools for visualizations of planned constructions in virtual reality. Audio engines accounting for sound propagation in the game engine environment are steadily developing and have recently been made available. The aim of this project is to simulate airborne sound insulation by extending the support of recently developed audio engines directed towards virtual reality applications. The case studied was airborne sound insulation between two adjacent rooms in a building, the sound transmitted to the receiving room through the building structure resulting from sound pressure exciting the structural elements in the adjacent source room into vibration. The receiving room composed modelled space in the game engine Unreal Engine and Steam Audio was the considered audio engine. Sound transmission was modelled by filtering based on calculations of transmission loss via direct and flanking paths using the model included in the standard EN 12354-1. It was verified that the filtering technique for modelling sound transmission reproduced attenuations in correspondence with the predicted transmission loss. Methodology was established to quantify the quality of the audio engine room acoustics simulations. A room acoustics simulation was evaluated by comparing the reverberation time derived from simulation with theoretical predictions and the simulated reverberation time showed fair agreement with Eyring’s formula above its frequency threshold. The quality of the simulation of airborne sound insulation was evaluated relating the sound field in simulation to insulation classification by the standardized level difference. The spectrum of the simulated standardized level difference was compared with the corresponding sound transmission calculation for a modelled scenario. The simulated data displayed noticeable deviations from the transmission calculation, caused by the audio engine room acoustics simulation. However, the simulated data exhibited cancellation of favourable and unfavourable deviations from the transmission calculation resulting in a mean difference across the spectrum below the just noticeable difference of about 1 dB. Single number ratings was compared and the simulated single number rating was within the standard deviation of how the transmission model calculates predictions for a corresponding practical scenario measured in situ. Thus, the simulated data shows potential and comparisons between simulated data, established room acoustics simulation software and in situ measurements should further be made to deduce whether the deviations entails defects in the airborne sound insulation prediction or is an error imposed by the audio engine room acoustics simulation.