Development of methods describing the impact sound insulation in wooden floors

SWEDEN AND FINLAND COOPERATE FOR BETTER SOUND INSULATION OF TIMBER FLOORS

Measuring sound in concrete constructions that consist of several floors has long been practiced, but after it was allowed in the 1990s to build multi-storey houses in timber, it turned out that the measurement methods could not really be translated between the different materials. The measured values ​​for impact sound insulation in timber buildings could be good, but still the residents were disturbed by noise from the neighbors.

Jörgen Olsson, RISE, has a PhD in the field and the project "Development of methods for describing the impact sound insulation in wooden floors" is to some extent a continuation of his doctoral work which was about impact sound insulation in timber buildings.

- In my doctoral project, I developed methods for measuring and calculating impact sound transmission, but we realized that to make it easier for companies and wood builders, we must solve the remaining challenges that exist when it comes to impact sound insulation in wooden buildings, says Jörgen Olsson.

DIFFICULT TO MEASURE IN LOWER FREQUENCIES

But what then does not work in the measurements? In short, the sound is measured in a room, where noise is created in the room above with a standardized machine that knocks on the floor. In the room below, the sound is measured with a microphone, but depending on whether the room is furnished or not, the sound level is affected - the more furniture, the higher the absorption of the sound, which in turn means a lower sound level. In order to still be able to make comparisons between different rooms and buildings, regardless of furniture, the reverberation time is measured with the help of a loudspeaker with loud noise. When the noise is switched off, it is measured how fast the sound disappears in the room, and with the help of the reverberation time it is possible to correct the impact sound measurement.

- The problem with this is that when you get down to low frequencies, which are generated in timber buildings, the classic measurement methods do not work because the sound behaves differently in frequencies below 100 hertz. When it comes to timber floors, we have to measure all the way down to 20 hertz to get the best match, says Jörgen Olsson.

The Swedish-Finnish collaborative project will therefore continue to work together with sound absorption at low frequencies, improve simulations to better predict which sound insulation is needed, and work with psychoacoustics of floors - that is, try to get a good match between measurement value and how people perceive the sound levels. Tests will include measurements of different types of wooden floors with a standardized tappaing machine that knocks on the floor and simulates sounds from heels. Also, since low frequencies can be more disturbing, for example soft, heavy balls released from a height of one meter will be used to simulate children playing and making noise, with a repeatable accuracy.

MORE INFORMATION

The project "Development of methods for describing the impact sound insulation in wooden floors" runs between April 2020 to April 2022 and is funded by the The Royal Swedish Agricultural Academy (KSLA) within the program "Tandem forest values". The project is a collaboration between RISE, Linnaeus University and Turku University of Applied Sciences (Finland). Smart Housing Småland supported in the application process and development of the project. Kirsi Jarnerö, process manager at Smart Housing Småland, contributed as an expert in the field, and is also project manager for the project.

CONTACT INFORMATION

Projektledare Kirsi Jarnerö, RISE: kirsi.jarnero@ri.se

Jörgen Olsson, RISE: jorgen.olsson@ri.se

Andreas Linderholt, Linnéuniversitetet: andreas.linderholt@lnu.se