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Low frequency sound pressure fields in small rooms in wooden buildings with dense and sparse joist floor spacings
SP Hållbar samhällsbyggnad.ORCID iD: 0000-0002-0019-4568
Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. (Maskinteknik)ORCID iD: 0000-0002-4404-5708
SP Hållbar samhällsbyggnad. (Byggteknik)
2015 (English)In: Proceedings of the Internoise 2015 conference, Society of Experimental Mechanics (SEM) , 2015Conference paper, Published paper (Refereed)
Abstract [en]

Using wood as the main construction material is a potential solution to achieve sustainable buildings. Previous research has shown that frequencies below 50 Hz are of significant importance for the perception of impact sound by residents living in multi-story buildings having light weight wooden frameworks. The standards used for impact sound measurements today are developed for diffuse fields above 50 Hz. For instance due to requirements concerning wall reflections, these methods are not applicable for low frequencies within small rooms. To improve measurement methods, it is important to know the nature of the full sound distribution in small rooms having wooden joist floors. Here, impact sound measurements with microphone arrays are made in two small office rooms having the same dimensions. The rooms represent two extremes in design of joist floors; one with closely spaced wood joists and the other with widely spaced joists. An impact ball is used for excitation the room being measured from the room above. The results show that there are significant variations in the sound pressure, especially in the vertical direction. Here, measurement techniques of impact sound in the low frequency range in small rooms in wooden buildings are evaluated and potential improvements are proposed.

Place, publisher, year, edition, pages
Society of Experimental Mechanics (SEM) , 2015.
Keyword [en]
low frequency, sound pressure, small rooms, wooden buildings, joist floor
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
URN: urn:nbn:se:lnu:diva-45737Scopus ID: 2-s2.0-84947589018OAI: oai:DiVA.org:lnu-45737DiVA: diva2:846689
Conference
Internoise, 9-12 August, 2015, San Francisco
Note

Ej belagd 20160411

Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2017-04-18Bibliographically approved
In thesis
1. Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements
Open this publication in new window or tab >>Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.

    Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.

    Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.

    The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.

    By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved

Place, publisher, year, edition, pages
Linnaeus University, 2016. 100 p.
Series
Faculty of Technology, Report, 46
Keyword
Low-frequency, impact sound, light weight floor, timber joist floor, tapping machine, multi-storey timber building, frequency response functions., Stegljud
National Category
Other Civil Engineering Fluid Mechanics and Acoustics
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-58068 (URN)978-91-88357-46-5 (ISBN)
Presentation
2016-11-30, Sal Tegner, Linnéuniversitet, hus H, Växjö, 10:00 (English)
Opponent
Supervisors
Projects
ProWoodSilent Timber BuildUrban TranquilityBioInnovation FBBB
Funder
Knowledge Foundation
Available from: 2016-11-15 Created: 2016-11-10 Last updated: 2017-09-01Bibliographically approved

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  • apa
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