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Low Frequency Force to Sound Pressure Transfer Function Measurements Using a Modified Tapping Machine on a Light Weight Wooden Joinst Floor
SP Technical Research Institute of Sweden.ORCID iD: 0000-0002-0019-4568
Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. (Maskinteknik)ORCID iD: 0000-0002-4404-5708
2016 (English)In: Proceedings of WCTE, World Conference on timber Engineering, August 22-25, 2016, Vienna, Austria, WCTE , 2016Conference paper (Other academic)
Abstract [en]

In recent years research has shown that low frequency impact sound is of significant importance for inhabitants´ perception of impact sound in buildings with light weight wooden joist floors. The tapping machine is well defined as an excitation device and is a standard tool for building acoustics. However, the excitation force spectrum generated for each individual floor is unknown when using a tapping machine. In order to increase the possibilities to compare simulations to impact sound measurements, there is a need for improvement of impact sound measurement methods. By measuring the input force spectrum by a modified tapping machine and the sound in the receiver room, transfer functions can be achieved.In the light weight wooden building used for the evaluation test of the proposed method, structural nonlinearities are evident in the frequency response functions stemming from different excitation levels. This implies that for accurate FRF-measurements in low frequencies, excitation magnitudes that are similar to these stemming from human excitations should preferably be used.

Place, publisher, year, edition, pages
WCTE , 2016.
Keyword [en]
Low-frequency impact sound, light weight wooden joist floor, tapping machine, frequency response functions
National Category
Applied Mechanics
Research subject
Technology (byts ev till Engineering), Mechanical Engineering
Identifiers
URN: urn:nbn:se:lnu:diva-57424OAI: oai:DiVA.org:lnu-57424DiVA: diva2:1037595
Conference
WCTE, World Conference on timber Engineering, August 22-25, 2016, Vienna, Austria
Projects
ProWood
Available from: 2016-10-17 Created: 2016-10-17 Last updated: 2016-11-15Bibliographically 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: 2016-11-24Bibliographically approved

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LOW FREQUENCY FORCE TO SOUND PRESSURE TRANSFER FUNCTION MEASUREMENTS USING A MODIFIED TAPPING MACHINE ON A LIGHT WEIGHT WOODEN JOIST FLOOR(614 kB)5 downloads
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