Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1986-11-13
1988-11-29
Fuller, Benjamin R.
Acoustics
Sound-modifying means
Muffler, fluid conducting type
181286, 181288, 181290, E04F 1704, F01N 102
Patent
active
047874732
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a sound attenuating box, particularly for the attenuation of sound waves which propagate within a fluid flowing in channels such as venting ducts. Such a sound attenuation box of the type to which the invention pertains, includes (a) at least one closed chamber establishing a cavity which is bounded on one side by an outer plate which can be stimulated to undergo vibrations in the audible range; and (b) at least one inner plate is arranged in the cavity of the chamber, running essentially parallel to the aforementioned outer plate, and partioning the cavity into two hollow chambers, which, however, are interconnected through a passage aperture traversing the internal plate. This passage aperture together with that partial chamber being separated by the inner from the outer plate, will constitute a so-called Helmholtz resonator that is tuned to vibrations in the audible range.
Industrial as well as home equipment provides for the transportation of air, exhaust fumes or the like through flow channels, containers, as well as openings. Such flow channels constitute frequently a very undesired transmission path for sound in air between the rooms interconnected by these flow channels. In particular, flow channels will transmit the noise produced by the flow generator itself, for example, a blower into otherwise closed rooms.
A rather effective sound attenuation can be obtained in such cases, in that the flow channels are covered with a sound absorbing lining. Upon utilizing a homogeneous lining of this type, the sound attenuation obtained therewith is proportional to the degree of absorption by the lining and the length of the flow channel as well as to the ratio between the circumference and the free cross-sectional areas of the flow channel. If technically realizable, the ratio between the periphery and the cross-sectional area of the free flow channel, is increased as much as possible through the insertion of additional sound absorbing partitions into the flow channel. Moreover, through this feature, the effective flow channel width is favorably reduced, because this width should always be significantly smaller than the wave length of the sound. The pressure drop produced through this kind of sound attenuation, however, must be kept as low as possible because otherwise a higher blower power has to be compensated, and that, in turn, entails a higher sound emission. These sound attenuation devices must, therefore, not exceed a particular thickness and should offer very little resistance to the flow.
In order to reduce to a minimum the friction losses which occur on the surface of the sound absorbing layer, as well as on the sound attenuating elements, it is desirable to make these surfaces completely planar, homogeneous, and smooth, i.e. without any apertures, steps, jumps, or the like.
Whenever precipitation deposits from the flow medium are to be expected, such as it may occur in air, gas, or vapor, then the sound absorbing element should not accept these deposits in any manner whatever, because deposits on the outside would not only increase the friction losses but, in the case of the usual sound absorber, their acoustic effectiveness would be considerably reduced. Even more important, however, is that the penetration of material from the flow medium into the interior of the sound absorber has to be avoided because these materials, when penetrating the absorber, will accumulate therein and, therefore, unfavorably interfer with the effectiveness of the sound absorber, or there may even be chemical reactions or other undesirable interactions. Hence, such a penetration of material should be avoided under all circumstances. For these reasons, as well as other important reasons having to do with safety technology such as fire proofing or hygenic-health aspects, it is desirable to provide an all around, particularly gas and water proof sealing of the sound absorbing lining elements as between the flow channels and the adjoining rooms.
In order to insure
REFERENCES:
patent: 3380206 (1968-04-01), Barnett
patent: 3834487 (1974-09-01), Hale
patent: 3983955 (1976-10-01), Vasiligevic
patent: 4084366 (1978-04-01), Saylor et al.
patent: 4301890 (1981-11-01), Zalas
patent: 4317503 (1983-03-01), Soderquist et al.
patent: 4410065 (1983-10-01), Harvey
Ackermann Ulrich
Fuchs Helmut V.
Rambausek Norbert
Fraunhofer Gesellschaft
Fuller Benjamin R.
Siegemund Ralf H.
LandOfFree
Sound attenuating box does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sound attenuating box, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sound attenuating box will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-357779