Air Damped Hearing Protector Earseal

Abstract

A hearing protector earcup having an earseal in the form of an annular envelope of highly flexible plastic sheet material held tightly against a rigid inwardly directed flange of the earcup. Capillary holes are provided through the rigid earcup flange in communication with larger openings in the envelope of the earseal wherewith airflow through the capillary orifices, into and from the earseal envelope, is exploited to achieve greater wearing comfort and strong damping of vibrations of the earcup resulting from excitation by ambient low-frequency sound waves. An additional small opening through an outer wall of the cup vents its interior.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Hearing protector devices with particular reference to improvements in hearing protector earcups and earseals therefor.

2. Description of the Prior Art

Heretofor it has been attempted to vent the envelopes of hearing protector earcup earseals with holes in the side of the envelopes which rest against the rigid earseal supporting flanges of the earcups. This form of earseal venting, however, fails to provide adequate and proper "breathing" of the earseal as a result of its earcup being pressed against a wearer's head during use whereby the earseal holes become closed by the supporting flange. Closure of the vent holes accordingly permits only a limited collapse of the earseal envelope upon application to the head and prevents it from readily conforming to the shape of the head. This results in less than perfect circumaural acoustical sealing and wearing discomfort. A further result of inadequate "breathing" of the earseal is "pumping" of the earcup toward and away from the wearer's head in resonance with external low frequency sound vibrations whereby optimum attenuation of ambient noise is not achieved.

Objectives of the present invention are to accomplish greater and longer lasting comfort in the wearing of earcup hearing protector devices and further to achieve greater attenuation of ambient noise, more particularly in the lower frequencies of sound.

The invention will be more fully understood by reference to the following detailed description taken in conjunction with the accompanying drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 is an illustration, in perspective, of use of a hearing protector earcup embodying the present invention;

FIG. 2 is a plan view of the hearing protector earcup showing a portion of its earseal lifted away from its main body for purposes of illustrating a featured part of the present construction;

FIG. 3 is a greatly enlarged fragmentary cross-sectional view of the hearing protector earcup taken along line 3--3 of FIG. 2; and

FIG. 4 is a graphic representation of one example of the improvement in hearing protection offered by the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1-3 of the drawing there is illustrated hearing protector earcup 10 which embodies the present invention. Earcup 10 is worn circumaurally and held tightly against the head with a spring steel-supporting headband 12 (FIG. 1) or its equivalent and comprises the usual rigid main body portion 14 having an earseal supporting flange 16 forming an elongated ear-receiving opening 18 in one side of cup 10.

Positioned against rigid flange 16 is annular earseal 20 having an inner contour size and shape corresponding approximately to that of opening 18 and an outer peripheral contour size and shape corresponding to that of the outer edge of flange 16, i.e., the outer peripheral contour of main body portion 14 of the earcup.

Earseal 20 comprises an annular peripherally heat sealed envelope 22 of thin and highly flexible plastic sheet material such as polyvinylchloride or its equivalent in function.

Envelope 22, being contoured to the particular size and shape of supporting flange 16, contains an internal cushion 24 of soft and highly compliant foam rubber or the like which, in a relaxed or uncompressed state, is of substantially uniform thickness throughout.

Earseal 20 is held against flange 16 by an annular rearwardly directed extension 26 (FIGS. 1 and 3) of a soft, flexible and somewhat elastic sheet material which is similar or identical to the material of envelope 22. Extension 26 is connected to envelope 22, e.g., by heat sealing, and holds envelope 22 against flange 16.

Referring more particularly to FIGS. 2 and 3, it will be seen that capillary holes 30 are formed in flange 16 behind wall 28 of envelope 22 and openings 32 are provided in wall 28 of envelope 22 to establish communication between the interior of envelope 22 and the main inner ear-receiving enclosure 34 of earcup 10. Openings 32, being of considerably larger size (e.g., 1/4 in. in diameter) than capillary holes 30, assure clear communication between envelope 22 and enclosure 34 at all times with an allowance for considerable accidental rotational misalignment of earseal 20 relative to flange 16 of earcup 10.

The term "capillary" is used herein to indicate the desirability of holes 30 being of small diametral size (e.g., within a range of from 0.006 in. to 0.015) wherewith air moving therethrough will meet with sufficient resistance to flow as to achieve strong damping of vibrations or motion of the earcup caused by resonance thereof to low frequency ambient sound. It is also pointed that the capillary holes 30 may be provided in numbers of 1, 2 or more and that use of the expression "number" hereinafter is to be interpreted as meaning several such holes or as few as only one. Two holes 30 have been shown in the drawing for purposes of illustration only.

With earcup 10 in use as shown in FIG. 1, for example, it is pressed firmly against the head by spring tension in headband 12 causing envelope 22 and its internally disposed soft foam rubber cushion 24 to quickly, accurately conform to the shape of areas of the head connected thereby due to venting of envelope 22 through openings 32 and capillary holes 30. This conformance of earseal 20 to the head shape provides the twofoldness of exceptional wearing comfort and superior noise attenuation; the latter being the result of tight circumaural sealing of the cup and vibration damping resulting from highly viscous (slow) airflow through capillary holes 30. The minute size of holes 30, offering resistance to the flow of air therethrough, attenuates the usually encountered "pumping" action of ear cups toward and away from the head of a wearer when the cups are in resonance with low frequency ambient noise.

Noise attenuation curves A and B (FIG. 4) graphically illustrate the results of actual testing of a hearing protector earcup such as that shown and described herein. Curve A represents the response (i.e., the amount of attenuation) in decibels of the experimental earcup with its capillary holes 30 sealed so as to prevent venting of the interior of envelope 22 through flange 16. Under identical conditions but with capillary holes 30 opened so as to permit venting between the interior of envelope 22 and enclosure 34 according to the present invention, curve B shows, with dotted outline, the considerable improvement in sound attenuation of lower frequency sound between 100 and 140 Hz. This improvement of 14 decibels or more, is directly attributable to the above-described inventive concept. It should be understood, however, that FIG. 4 is presented for illustration purposes only and does not represent limitations of the present invention.

Since a perfect circumaural seal may cause an uncomfortable overpressure to develop at the eardrum when an inwardly directed holding force is applied to the earcup by headband 12, for example, the present invention also contemplates venting ear enclosure 34. In this regard, a small diameter hole 36 (FIG. 3) through an outer wall of earcup 10 may be incorporated to maintain substantially constant earcup inner and outer air pressures.

It has been found that the inclusion of a 0.013 inch diameter hole 36, in a 1/8 inch thickness of wall material of earcup 10 will accomplish desirable venting of enclosure 34 without effecting the noise attenuating capabilities of earcup 10. Hole 36 may be located beneath dust cap 38 (FIGS. 1 and 3) to avoid plugging thereof by direct exposure to dust and/or other foreign matter.

Claims

I claim:

1. The improvement in a hearing protector earcup having an earseal in the form of an annular envelope of flexible sheet material held against a rigid inwardly directed lateral flange of the earcup comprising:

said rigid flange having a number of capillary holes extending therethrough and said one side of said earseal envelope having at least one opening therein, said opening being aligned with one of said capillary holes wherewith communication between the interiors of said envelope and said earcup through said opening and said one capillary hole is established for achieving a damping of vibrations of the earcup and enhanced wearing comfort.

2. The improvement in a hearing protector earcup according to claim 1 wherein said opening in said earseal envelope is of a substantially larger size than the diametral size of any one of said capillary holes.

3. The improvement in a hearing protector earcup according to claim 1 wherein a plurality of said capillary holes and a corresponding number of said openings are provided in said flange and earseal envelope respectively, said openings being disposed in at least approximate alignment with said capillary holes and further each being of substantially larger size than the diametral dimension of any one of said capillary holes.

4. The improvement in a hearing protector earcup according to claim 1 including a ventilative opening extending through a side of said earcup for maintaining substantially equalized air pressure internally and externally of said earcup.

5. The improvement in a hearing protector earcup according to claim 4 still further including a dust cover on said earcup extending over said ventilative opening for protection thereof against collection of ambient foreign matter.