Acoustic Materials in the Built Environment

Acoustic properties of materials that are located either inside or outside of buildings determine the acoustic experience of the built environment. In order to design indoor and outdoor environments with a desirable acoustic performance, it is important to place acoustic materials such as sound-absorbing or -insulating panels, carpets, curtains, and even green plants in a proper manner. The successful design of an acoustic landscape is possible when we know the exact acoustic properties of the materials and how the sound propagates inside and through materials. In addition to that, the development of highly functional acoustic materials is essential for enhancement of the sound quality in the built environment. With respect to these aspects, the building acoustics group is working on the following topics.

Acoustic Material Design

Sound-absorbing or -insulating materials, e.g., porous layers and micro-perforated panels, are widely used throughout the built environment for noise reduction. However, their performance is often restricted by the available space, because it is typically required to use materials of unrealistically high mass or volume to reduce the noise, especially in the low-frequency range. To overcome these limitations, acoustic material designs targeted at reducing the noise in low and broad frequency ranges while occupying a much smaller volume compared to the conventional materials are being developed.

Damper systems to reduce low-frequency transmission through LWF
Multiple porosities in micro-perforated panel for broadband sound absorption

Acoustic Material Characterization

The need for accurate measurement methods to estimate the acoustic properties of materials is growing with the development of numerical simulations in room acoustics. Especially, in situ measurement methods are receiving great attention due to their capability to retrieve the acoustic properties of materials regardless of the mounting conditions. The incorporation of suitable model fitting, which is chosen in consideration of the acoustic wave behavior in the materials, into the in situ measurement results makes it possible to obtain reliable results over a broad range of frequency.

In situ characterization of the acousticimpedance of vegetated roofs
In situ measurement setup for a porous layer (left) and model fitting of the acoustical properties (right)

Computational Methods for Building Acoustic Simulation

Wave-based simulations provide a numerical approximation of the actual wave phenomena such as reflection, transmission, diffraction, and interference. These highly accurate methods can be used to determine wave behavior through various acoustic media, for example, air-borne sound transmitted through a structural plate and then re-radiated in another room or sound transmission through privacy screens in an open office environment.

Acoustic radiation by a vibrating plate (left) and noise transmission in a building (right)