Acoustics – Sound-modifying means – Sound absorbing panels
Patent
1980-08-11
1984-04-10
Fuller, Benjamin R.
Acoustics
Sound-modifying means
Sound absorbing panels
181288, 181290, 181293, 181294, E04B 182, C04B 4300
Patent
active
044415818
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a component for airborne-sound insulation in plate or sheet-like form for incorporation into walls and ceilings.
The extent of the airborne-sound insulation of a wall is mainly dependent on its weight per unit area, i.e. its mass. In theory it is possible to derive from this the known mass law which reproduces the relationship between the weight per unit area of a wall and the transmission loss. However, measurements taken under practical conditions have shown that the transmission losses calculated according to the mass law are not achieved, because no account is taken of the elastic wall characteristics. If, with rising sound generating frequency, the wavelength in air becomes smaller than the flexural wavelength of the wall at a given frequency coincidence effects occur, resulting from the resonance between the acoustic excitation of the wall and the free flexural vibrations thereof and significantly reduce the transmission loss. This breakdown in the mass law due to coincidence effects is between 60 and 3200 Hz for most materials used in partitioning walls and it would appear impossible to reach the theoretical transmission loss in this range. Most plate-like wall or door elements have a weight per unit area of 6-40 kg/m.sup.2. Comprehensive measurements for such weights per unit area have shown that most of the coincidence effects i.e. the reduction of sound insulation occur in the above-indicated frequency range.
Considerable efforts have been made to increase the airborne-sound insulation to plate-like components. In principle this can be achieved by increasing the weight per unit area of a plate by covering it with an additional mass and/or by reducing its inherent rigidity, so that the breakdown in the mass law only occurs at a frequency above 3000 Hz.
It is known to join a plate to a lead sheet, which leads to a very good effect in the case of thin support plates because breakdown occurs over 3000 Hz. In the case of thicker plates breakdown occurs at below 3000 Hz and the per se known reduction of the airborne sound insulation occurs, so that the transmission loss is well below the theoretical value.
It is also known to increase the weight of a plate with sandbags. Although this initially leads to a good action in time this action is reduced, because cavities occur due to settlement of the sand, so that the transmission loss drops. Satisfactory results are also not obtained when cavities in extruded plates are filled with sand, because the sand is deposited in the relatively large cavities which leads to a reduction in the sound insulation. The one-sided crosswise slotting of plates is also known, which leads to a displacement of the frequencies in which the coincidence effects occur towards higher frequencies. Insulating sheets are known which are made from heavy plastics or have granular materials incorporated into the plastic, but here again the coincidence effects occur in the indicated frequency range.
The problem of the invention is to so construct a component of the aforementioned type that coincidence effects substantially no longer occur in the indicated frequency range of 60-3200 Hz.
According to the invention this problem is solved in that the component has a plurality of chambers separated from one another by walls and filled with a granular or particulate material.
The invention is described in greater detail hereinafter relative to a number of embodiments and the attached drawings, wherein shown:
FIG. 1 a view of a component for airborne-sound insulation made from corrugated board.
FIG. 2 a section along the line II--II of FIG. 1 on a greatly enlarged scale.
FIG. 3 a view of a further component for airborne-sound insulation.
FIG. 4 a sectional along the line IV--IV of FIG. 3 on a greatly enlarged scale.
FIG. 5 a three-dimensioned view of a third component for airborne-sound insulation in the form of a soft fibreboard.
FIG. 6 An exploded three-dimensional view of a further component for airborne-sound insulation in the form of stitched material webs.
The inve
REFERENCES:
patent: 2973295 (1961-02-01), Rodgers, Jr.
patent: 4241806 (1980-12-01), Metzger
Fuller Benjamin R.
Hawa AG.
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