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- Johansson, Carin, et al.
(författare)
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Development of a lightweight wooden joist floor with high impact noise insulation
- 1994
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:1, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the results of a project for the development of a lightweight wooden joist floor. The work has been carried out by the optimization of each of the variables which are important for sound insulation and has resulted in the construction of a framing of joists which has good impact sound insulation, small dimensions, can be constructed in a simple way at low cost and can be assembled in an easy and safe way. Forty-five different constructions and combinations were tested in the laboratory. The optimal construction was finally tested in several blocks of flats. In order for the construction to meet the Swedish Building Standards for sound insulation, the impact noise index Ii must not exceed 63 dB. The final construction had an index Ii of 52 dB in the laboratory and 53–58 dB in the field, and was thus approximately 10 dB better that the standard limit for impact noise between adjoining flats. The total weight of the construction is only 60 kg/m2 and the total thickness is 342 mm. Furthermore the framing of joists is economical and practical to manufacture in factories, is easy to transport without deformation and is easy to install in the building on the site.
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- Tingvall, Bror, et al.
(författare)
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Noise emissions from snowmobiles
- 1994
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Ingår i: Noise - quantity and quality. - Poughkeepsie, NY : Noise control foundation. ; , s. 407-410
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Konferensbidrag (refereegranskat)
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- Ågren, Anders, et al.
(författare)
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Experimental study of repeatability errors in 3D sound intensity measurements in narrow frequency bands
- 1994
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:2, s. 95-111
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Tidskriftsartikel (refereegranskat)abstract
- When investigating the 2D or 3D intensity of complex ‘real life’ noise sources, rather than the intensity normal to a surface, to obtain more detailed information about the radiated sound field great care has to be taken both in measuring and in interpreting the results. In this study it is shown that in measurements of 3D intensity for fixed points and in narrow frequency bands, large errors can be expected for a well-defined simple source if the positioning is imprecise and for a complex source even if the positioning device and the probe are of highest quality. Comparisons have been made between a two-microphone and a six-microphone probe, hand-held and robot-controlled. The comparisons show that, except for the case of an ideal measurement with a simple source and a high-precision robot, significant errors can be expected for all the tested measurement cases. The measurements also show that the positioning of the microphone is of major importance for the repeatability accuracy. The accuracy obtained with a 3D-probe is notably better than with a 1D-probe. The errors when measuring the complex source with a robot-controlled 3D-probe, however, are still so high, especially for the non-dominant directions, that interpretations have to be made with great care. Under non-ideal measurement conditions, the errors are found to be exponentially dependent upon the sound field pressure/intensity relationship (the pI-index).
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