Acoustics – Diaphragm and enclosure – With sound-absorbing means
Patent
1984-11-02
1987-04-14
Fuller, Benjamin R.
Acoustics
Diaphragm and enclosure
With sound-absorbing means
181149, 181199, 181296, H05K 500
Patent
active
046571086
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a constant pressure device.
More particularly, the invention is concerned with techniques for eliminating or substantially eliminating pressure variations in an essentially closed volume, which variations would tend to occur when the capacity of said volume is reduced. For instance, the interior of a loudspeaker box is an essentially closed volume which is effectively reduced in volume when the loudspeaker cones make excursions into the interior of the box. Such excursions tend therefore to increase the pressure in the box and by the techniques of the invention, such pressure variations are significantly reduced.
According to the present invention there is provided a loudspeaker assembly comprising communication with the interior of the box, least one component of the gas or vapour to a degree which is dependent upon the partial pressure thereof whereby pressure increases in the gas or vapour in the box resulting from excursions of said loudspeaker into the box are relatively low because of increased adsorption of said component on said mass of material.
The invention also provides a method of stabilizing pressure in an effectively closed volume which contains a gas or vapour and is subject to variations in volume comprising the step of introducing into the volume a mass of adsorbent material into the volume, said adsorbent material being selected whereby at least one component of the gas or vapour is adsorbed thereon to a degree which depends upon the partial pressure of said component, whereby pressure variations consequent upon said variations in volume are less than those which would occur if said material were not present in the volume.
The invention further provides a pressure stabilizing device comprising or vapour said adsorbent material being such that at least a component of said gas or vapour is adsorbable thereon to a degree which is dependent on the partial pressure of said component whereby the pressure in said volume is generally independent of changes in the volume of said space.
The expression "essentially closed" is intended to cover an arrangement in which the aforementioned gas or vapour is located within gas or vapour tight surroundings so that there is no flow of gas or vapour to or from those surroundings. Alternatively, the arrangement could be such that there is flow of gas or vapour at to and from those surrounding at a relatively low rate whereby the steady state pressure of the gas or vapour is equal to ambient but when the gas or vapour is subjected to pressure variations at higher frequencies say in the range 20 to 100 Hz or above there is no flow of gas or vapour to and from the surroundings and the gas or vapour is thus effectively within a closed volume at those frequencies.
The invention will now be further described with reference to its application in the field of loudspeakers and with reference to the accompanying drawings, in which:
FIG. 1 is a schematic cross-sectional view through a loudspeaker assembly constructed in accordance with with the invention;
FIG. 2 is a schematic cross-sectional view taken along the line 2--2;
FIG. 3 is a schematic view of an air trap which forms part of the loudspeaker shown in FIG. 1;
FIG. 4 is a graph showing the loudspeaker impedance as a function of frequency for various arrangements;
FIG. 5 is a graph showing the sound pressure level as a function of frequency for a loudspeaker of the invention compared to a known loudspeaker; and
FIG. 6 is a graph of a parameter C as a function of frequency, the parameter C being related to the factor by which pressure variations are reduced within the speaker enclosure in accordance with the techniques of the invention.
The loudspeaker assembly illustrated in FIG. 1 comprises a loudspeaker box 2 having a rear wall 4, bottom 6, top 8 and side walls 10. The front face of the box is spanned by a baffle 12 upon which a high frequency speaker 14 and low frequency speaker 16 are mounted in a generally conventional manner. In use the cone 18 of the low frequency speaker 16 makes
REFERENCES:
patent: 3675398 (1972-07-01), Giarrizzo
patent: 4004094 (1977-01-01), Ott
patent: 4101736 (1978-07-01), Czerwinski
patent: 4356882 (1982-11-01), Allen
patent: 4450929 (1984-05-01), Marrs
patent: 4506759 (1985-03-01), Fatovic
LandOfFree
Constant pressure device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Constant pressure device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constant pressure device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1778672