EAR PROTECTIVE DEVICE
United States Patent 3842829
A device to be worn within the external auditory canal for the purpose of protecting the ear from high intensity and impact sounds. Under normal conditions transmission is through a diaphragm with minimal attenuation. Under high intensity noise levels the diaphragm is damped by approach to a support area axially separated from the free position of the diaphragm, the film of air between the support surface and the diaphragm introducing viscous damping. Under high impact and extremely high sound levels, the diaphragm rests upon the support surface and the effective diameter of the diaphragm is thereby reduced giving a marked further reduction in sound transmission, the diaphragm becoming in effect a sound actuated poppet valve.
US Patent References:
/1148849.html
Mallock - August 1915 - 1148849
/1279396.html
Michelson and Wilson - September 1918 - 1279396
Vibratory-diaphragm controller
Williamson - May 1920 - 1340471
Acoustic guard
Rosenblatt - November 1944 - 2361963
Hearing aid plastic ear pieces
Henderson - June 1960 - 2939923
/1148849.html
Mallock - August 1915 - 1148849
/1279396.html
Michelson and Wilson - September 1918 - 1279396
Vibratory-diaphragm controller
Williamson - May 1920 - 1340471
Acoustic guard
Rosenblatt - November 1944 - 2361963
Hearing aid plastic ear pieces
Henderson - June 1960 - 2939923
Application Number:
05/199908
Publication Date:
10/22/1974
Filing Date:
11/18/1971
View Patent Images:
Export Citation:
Primary Class:
International Classes:
A61F11/08; A61F11/00; A61F11/02
Field of Search:
128/151,152 2/209 179/180,181 181/22,23 179/17E,182
Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Recla, Henry J.
Claims:
I claim
1. A device for protecting the ear comprising:
2. A device for protecting the ear comprising:
1. A device for protecting the ear comprising:
2. A device for protecting the ear comprising:
Description:
BACKGROUND OF THE INVENTION
Devices for the protection of the ear are not new but the general approach has been that if sound is to be kept from the ear all sound should be forbidden entrance. Most devices have taken the form of headstrap-connected ear muffs with great effort being expended to make them so comfortable that the wearer would accept their bulk. Where the physical bulk was not to be tolerated ear plugs have been used, generally solid. These devices have the common failing of placing the wearer out of communication with those around him. A second class of devices worn within the ear has depended for their action upon physical valve structures, stiff and heavy in relation to the forces available to move them.
The subject invention makes use of a very thin plastic diaphragm or pellicle as the sound responsive element. It is supported in such a manner as to permit unrestrained vibration in response to low intensity sound so that ordinary speech, for example, is transmitted without significant modification. Adjacent the center of the diaphragm and spaced slightly from it is a diaphragm stop surface. As the diaphragm approaches this surface the air film over the stop provides a viscous damping cushion which effectively limits the loudness of this action. When this sound level is exceeded the diaphragm actually may contact the stop and in doing so its effective diameter is greatly reduced giving high attenuation to the sound but not totally eliminating it. Thus a person working in a noisy area can still be aware of sounds louder than the ambient and take corrective action if necessary.
The typical device heretofore has been uncomfortable to wear for extended periods. The ear muffs covered so much of the head area as to interfere with body surface cooling. The internally worn devices have generally caused discomfort when worn for more than a short time by interference with circulation. As will be detailed below, this invention includes improvements in the body contacting element to overcome these shortcomings.
The primary object of this invention is to provide a device which will protect the users hearing during long exposure in high ambient noise areas.
Another object is to highly attenuate and limit impact sounds and excessive pressure changes before they reach the ear drum, without totally suppressing their sound.
Another object is to provide such protection while permitting the passage of sound of lower intensity essentially unaltered.
Still another object is to provide comfort in such a device so that it may be worn for long periods of time without harm or discomfort.
Another object is to provide for ease of installation and removal of the device by the wearer.
Yet another object is to provide a device of the character described that will be simple and economical to manufacture.
An advantage of this device over solid ear plugs or ear muffs is that the wearer is not wholly out of communication while wearing the device. There is a safety factor in being able to hear all that is said, for example on a firing range, while blocking all potentially damaging sound from the ears. The same would hold true in industrial operations such as near punch presses and forges.
Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a fragmentary sectional view of the device of this invention shown in place within the external auditory canal;
FIG. 2 is a vertical section view of the device embodying this invention taken in a plane through the cylindrical axis;
FIG. 3 is a vertical section of one modified form of one element of the invention.
FIG. 4 is a vertical section of a modified form of another element of the invention.
Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the several views, the device embodying this invention is generally indicated at 1 in FIG. 1. It comprises a first body member generally indicated at 2 in FIG. 2, a cap-shaped second body member generally indicated at 3, a diaphragm generally indicated at 4 and a support structure generally indicated at 5. FIG. 1 shows the support structure, 5, deformed into a cushioning surround for the device as worn.
FIG. 2 shows the body member 2, of generally cylindrical form, and includes an axial bore, 10, therethrough enlarged at one end to a shallow second bore, 11. The outer diameter, 15, of the body is reduced beginning at one end and for a substantial distance as indicated at 16 for a fit within cap 3. At the opposite end the diameter is further reduced at 17 and the outer corner rounded at 18. A circumferential groove, 19, is formed at the inner end of of surface 17 for the purpose of retaining the support material generally indicated at 5. A heavy chamfer, 20, is formed between the outer diameter 15 and the adjacent wall of groove 19 as an aid in control of the shape of the support structure when the device is worn. A groove, 12, is formed in the surface of the outer end of the portion of reduced diameter 16, separating this surface into two concentric ring surfaces 13 and 14. Additional machining of surface 14 reduces its plane inwardly from the plane defined by the ring 13. The diaphragm 4 is held against surface 13 by the cap 3 and surface 14 then has a small clearance from the diaphragm. The groove 12 provides a very large clearance for the diaphragm to prevent loading of the diaphragm under low noise conditions. Under high noise and impact conditions the inner portion of the diaphragm deflects to rest upon surface 14.
The cap 3 includes an axial bore 24. This bore is enlarged at the body receiving end to bore 25. At the inboard end of bore 25 a shallow bore 26 is formed to provide diaphragm clearance and to produce a step, 27, corresponding in inner dimension with surface 13. At the other end bore 24 is enlarged in a second shallow bore 28. The outer diameter 23 is reduced and contoured at one end as indicated at 31 and a groove 32 of lesser diameter formed inwardly of the end, the flange thus formed serving as a grasping means whereby the unit may be easily held by the finger nails for insertion or removal by the wearer.
The diaphragm or pellicle 4 is preferably of a film plastic material and when assembled in the device is firmly gripped between surfaces 13 and 27 and in spaced relationship from surface 14.
The support structure 5 is preferably comprised of two centrally perforated discs, 21 and 22, of closed pore cellular elastomer such as polyethylene, polyurethane or polyvinyl material. These discs are mounted to body member 2 by stretching over diameter 17 to seat in groove 19.
Assembly of the cup member 3 to the body member 2 may be by any suitable means such as press fitting or pressing over a knurl as represented at 43.
Referring now to FIG. 3 a modification of this invention is shown wherein adjustment of the diaphragm clearance is provided. The first body is now comprised of two parts, an inner member generally designated 6 and an outer member generally indicated at 7. These two members coact in telescoping relation of the outer diameter 35 of the inner member within the bore 36 of the outer member. In addition the inner member 6 has screw threads, 37 engaging in internal screw threads 38 within bore 36 of member 7. When these parts are threaded fully home the surfaces 40 on 6 and 41 on 7 come into abuttment and provide a limit stop. The parts are so proportioned that the surface 14 on the end of the inner member will be within the plane of the surface 13 of the outer member. The bore 37 of the outer member is enlarged to a shallow bore 39 adjacent surface 41. A wave washer, 42, is contained within bore 37, its free height being greater than the depth of the bore, for the purpose of providing an axial force to develop friction between threads 36 and 38. The friction is for the purpose of holding the parts in fixed relationship with the surface 14 a selected distance from the plane of surface 13 after the members have been rotated relative to one another for control of diaphragm clearance and hence the level of sound cut-off.
Since clearances in the diaphragm area are small it has been found advantageous to provide mechanical filters to keep out small foreign particles. Within bore 11 a fine fabric filter, 33, is fitted and held in place by a press fitted ring member, 34. A similar filter, 29, is fitted within bore 28 and held in place by ring 30. It is emphasized that these are mechanical not acoustic filters and the operating advantages of this device are readily apparent even in the absence of these filters.
In FIG. 4 a modified form of cap is generally indicated at 8. In this modification the bore 24 is of a size corresponding to that of bore 10 and a groove 44, similar in function to groove 12, is machined into the inboard face of bore 25 defining diaphragm supporting surface 27 and a second concentric surface 45. The surface 45 is further machined to bring its plane slightly inward of the plane of surface 27 to become a second diaphragm limiting surface. In an assembled device, surface 45 will function as a second viscous damping surface for the diaphragm on its outward excursion and add to the overall damping effectiveness for loud sounds. It will also perform as a limit stop for excessive negative pressure gradients whereas surface 14 is effective for the positive pressure waves.
In operation under low noise conditions this device acts as a simple repeater. Sound appearing at the diaphragm, which approximates the ear drum in size, is directly coupled in one to one relationship through the air column within the external auditory canal. Under high intensity sound the diaphragm moves far enough in its vibration to contact the support surface 14 or support surfaces 14 and 45, and the effect is of clipping the high intensity sound peaks. No additional sound or rattle is introduced because a degree of damping is produced in the air film over the surface 14 just before actual contact, surface 14 having a finite width. Finally under extremely intense sound and impact the diaphragm actually seats upon surface 14. When this occurs the sound is not only limited but actually reduced since the effective diaphragm diameter has dropped to the diameter of bore 10. Bore 10, for instance, might be about one-third of the free diaphragm diameter. Since the diaphragm motion will vary as the fourth power of its radius, this will result in a reduction of 81:1 and since the piston effect is now that of a one-third diameter piston a further reduction of 9:1 takes place in the air column for a new reduction of the order of 700:1 in the energy reaching the ear drum. Reduction of bore 10 diameter to one-tenth of the free diameter of the diaphragm would result in an over-all sound reduction of 8,000:1. It is pointed out that as the damping surface 14 is made wider the degree of damping is increased. By changes in dimension of bore diameter 10 and of the width of surface 14 means are provided for the design of a protective device having a desired transition point and degree of sound reduction.
The selection of material for the supporting structure, 5, deserves attention. It must be conformable because the meatus surfaces of no two auditory canals are alike in either size or shape. It must be soft so as not to cause pressure points. The surface must not be so smooth as to be slippery nor as to cause sweating or wax formation in the canal. It must be sound absorbant so as not to pass sound around the device and thus defeat its purpose. A closed cell polyvinyl elastomer possesses all of these qualities and in addition it has the necessary elasticity to provide for a very simple means of assembly. This latter is of significance in that it makes replacement of this part by the wearer practical when desired. Closed cell polyethylene is somewhat less elastic but has the quality of high conformability and gives a high degree of comfort.
It has been found advantageous to cut the parts for the support structure 15, from cut sheets of the elastomeric material. They are made as round discs with a central perforation. Two are preferred, not cemented surface to surface, as this has been found to produce a much more conformable assembly than when either thicker or cemented material is used and is far superior to molded material which carries a skin surface. When in the ear the direct transmission of sound due to motion of the device in its cushion is negligible except when walking when each step is audible. Normal sounds do not drive the device as a whole since its mass is more than 20,000 times the mass of the diaphragm.
Plastic material is the material of choice for the diaphragm, again for several reasons. First in importance is its low elastic modulus, less than 600,000 p.s.i., as compared with 10,000,000 for Aluminum, for example, since it is desirable to have a diaphragm with as large a central excursion as possible where the diameter is strictly limited by the wearing requirement. Second, its low density is advantageous in keeping the mass to a minimum, important in getting a sensitive diaphragm with good frequency response. The stability of the material under various conditions is a further advantage. Another advantage in plastic material is the wide selection of hardness which enable the selection of various sound response characteristics where desired. Finally, the permeability of these materials to water vapor and gasses is not to be found in metal foils. Having the diaphragm of permeable material aids in avoiding moisture buildup within the ear canal.
To give dimension to this device it has been found that various diaphragm materials of from 0.001 inch to 0.0015 inch in thickness function without distortion of sound of low level. Each performed satisfactorily against high level sound and impace noises with a clearance of about 0.001 inch between the free diaphragm and the surface 14.
From the foregoing description it will be seen that a device formed in accordance with the above teachings is simple in construction and relatively economical to manufacture. It is apparent that all of the objects and advantages of the invention have been accomplished. It will also be apparent, however, that changes may be made in the details of construction and arrangement of parts shown and described without departing from the spirit of the invention as expressed in the accompanying claims. Therefore, it is to be understood that all matter set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
Devices for the protection of the ear are not new but the general approach has been that if sound is to be kept from the ear all sound should be forbidden entrance. Most devices have taken the form of headstrap-connected ear muffs with great effort being expended to make them so comfortable that the wearer would accept their bulk. Where the physical bulk was not to be tolerated ear plugs have been used, generally solid. These devices have the common failing of placing the wearer out of communication with those around him. A second class of devices worn within the ear has depended for their action upon physical valve structures, stiff and heavy in relation to the forces available to move them.
The subject invention makes use of a very thin plastic diaphragm or pellicle as the sound responsive element. It is supported in such a manner as to permit unrestrained vibration in response to low intensity sound so that ordinary speech, for example, is transmitted without significant modification. Adjacent the center of the diaphragm and spaced slightly from it is a diaphragm stop surface. As the diaphragm approaches this surface the air film over the stop provides a viscous damping cushion which effectively limits the loudness of this action. When this sound level is exceeded the diaphragm actually may contact the stop and in doing so its effective diameter is greatly reduced giving high attenuation to the sound but not totally eliminating it. Thus a person working in a noisy area can still be aware of sounds louder than the ambient and take corrective action if necessary.
The typical device heretofore has been uncomfortable to wear for extended periods. The ear muffs covered so much of the head area as to interfere with body surface cooling. The internally worn devices have generally caused discomfort when worn for more than a short time by interference with circulation. As will be detailed below, this invention includes improvements in the body contacting element to overcome these shortcomings.
The primary object of this invention is to provide a device which will protect the users hearing during long exposure in high ambient noise areas.
Another object is to highly attenuate and limit impact sounds and excessive pressure changes before they reach the ear drum, without totally suppressing their sound.
Another object is to provide such protection while permitting the passage of sound of lower intensity essentially unaltered.
Still another object is to provide comfort in such a device so that it may be worn for long periods of time without harm or discomfort.
Another object is to provide for ease of installation and removal of the device by the wearer.
Yet another object is to provide a device of the character described that will be simple and economical to manufacture.
An advantage of this device over solid ear plugs or ear muffs is that the wearer is not wholly out of communication while wearing the device. There is a safety factor in being able to hear all that is said, for example on a firing range, while blocking all potentially damaging sound from the ears. The same would hold true in industrial operations such as near punch presses and forges.
Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a fragmentary sectional view of the device of this invention shown in place within the external auditory canal;
FIG. 2 is a vertical section view of the device embodying this invention taken in a plane through the cylindrical axis;
FIG. 3 is a vertical section of one modified form of one element of the invention.
FIG. 4 is a vertical section of a modified form of another element of the invention.
Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the several views, the device embodying this invention is generally indicated at 1 in FIG. 1. It comprises a first body member generally indicated at 2 in FIG. 2, a cap-shaped second body member generally indicated at 3, a diaphragm generally indicated at 4 and a support structure generally indicated at 5. FIG. 1 shows the support structure, 5, deformed into a cushioning surround for the device as worn.
FIG. 2 shows the body member 2, of generally cylindrical form, and includes an axial bore, 10, therethrough enlarged at one end to a shallow second bore, 11. The outer diameter, 15, of the body is reduced beginning at one end and for a substantial distance as indicated at 16 for a fit within cap 3. At the opposite end the diameter is further reduced at 17 and the outer corner rounded at 18. A circumferential groove, 19, is formed at the inner end of of surface 17 for the purpose of retaining the support material generally indicated at 5. A heavy chamfer, 20, is formed between the outer diameter 15 and the adjacent wall of groove 19 as an aid in control of the shape of the support structure when the device is worn. A groove, 12, is formed in the surface of the outer end of the portion of reduced diameter 16, separating this surface into two concentric ring surfaces 13 and 14. Additional machining of surface 14 reduces its plane inwardly from the plane defined by the ring 13. The diaphragm 4 is held against surface 13 by the cap 3 and surface 14 then has a small clearance from the diaphragm. The groove 12 provides a very large clearance for the diaphragm to prevent loading of the diaphragm under low noise conditions. Under high noise and impact conditions the inner portion of the diaphragm deflects to rest upon surface 14.
The cap 3 includes an axial bore 24. This bore is enlarged at the body receiving end to bore 25. At the inboard end of bore 25 a shallow bore 26 is formed to provide diaphragm clearance and to produce a step, 27, corresponding in inner dimension with surface 13. At the other end bore 24 is enlarged in a second shallow bore 28. The outer diameter 23 is reduced and contoured at one end as indicated at 31 and a groove 32 of lesser diameter formed inwardly of the end, the flange thus formed serving as a grasping means whereby the unit may be easily held by the finger nails for insertion or removal by the wearer.
The diaphragm or pellicle 4 is preferably of a film plastic material and when assembled in the device is firmly gripped between surfaces 13 and 27 and in spaced relationship from surface 14.
The support structure 5 is preferably comprised of two centrally perforated discs, 21 and 22, of closed pore cellular elastomer such as polyethylene, polyurethane or polyvinyl material. These discs are mounted to body member 2 by stretching over diameter 17 to seat in groove 19.
Assembly of the cup member 3 to the body member 2 may be by any suitable means such as press fitting or pressing over a knurl as represented at 43.
Referring now to FIG. 3 a modification of this invention is shown wherein adjustment of the diaphragm clearance is provided. The first body is now comprised of two parts, an inner member generally designated 6 and an outer member generally indicated at 7. These two members coact in telescoping relation of the outer diameter 35 of the inner member within the bore 36 of the outer member. In addition the inner member 6 has screw threads, 37 engaging in internal screw threads 38 within bore 36 of member 7. When these parts are threaded fully home the surfaces 40 on 6 and 41 on 7 come into abuttment and provide a limit stop. The parts are so proportioned that the surface 14 on the end of the inner member will be within the plane of the surface 13 of the outer member. The bore 37 of the outer member is enlarged to a shallow bore 39 adjacent surface 41. A wave washer, 42, is contained within bore 37, its free height being greater than the depth of the bore, for the purpose of providing an axial force to develop friction between threads 36 and 38. The friction is for the purpose of holding the parts in fixed relationship with the surface 14 a selected distance from the plane of surface 13 after the members have been rotated relative to one another for control of diaphragm clearance and hence the level of sound cut-off.
Since clearances in the diaphragm area are small it has been found advantageous to provide mechanical filters to keep out small foreign particles. Within bore 11 a fine fabric filter, 33, is fitted and held in place by a press fitted ring member, 34. A similar filter, 29, is fitted within bore 28 and held in place by ring 30. It is emphasized that these are mechanical not acoustic filters and the operating advantages of this device are readily apparent even in the absence of these filters.
In FIG. 4 a modified form of cap is generally indicated at 8. In this modification the bore 24 is of a size corresponding to that of bore 10 and a groove 44, similar in function to groove 12, is machined into the inboard face of bore 25 defining diaphragm supporting surface 27 and a second concentric surface 45. The surface 45 is further machined to bring its plane slightly inward of the plane of surface 27 to become a second diaphragm limiting surface. In an assembled device, surface 45 will function as a second viscous damping surface for the diaphragm on its outward excursion and add to the overall damping effectiveness for loud sounds. It will also perform as a limit stop for excessive negative pressure gradients whereas surface 14 is effective for the positive pressure waves.
In operation under low noise conditions this device acts as a simple repeater. Sound appearing at the diaphragm, which approximates the ear drum in size, is directly coupled in one to one relationship through the air column within the external auditory canal. Under high intensity sound the diaphragm moves far enough in its vibration to contact the support surface 14 or support surfaces 14 and 45, and the effect is of clipping the high intensity sound peaks. No additional sound or rattle is introduced because a degree of damping is produced in the air film over the surface 14 just before actual contact, surface 14 having a finite width. Finally under extremely intense sound and impact the diaphragm actually seats upon surface 14. When this occurs the sound is not only limited but actually reduced since the effective diaphragm diameter has dropped to the diameter of bore 10. Bore 10, for instance, might be about one-third of the free diaphragm diameter. Since the diaphragm motion will vary as the fourth power of its radius, this will result in a reduction of 81:1 and since the piston effect is now that of a one-third diameter piston a further reduction of 9:1 takes place in the air column for a new reduction of the order of 700:1 in the energy reaching the ear drum. Reduction of bore 10 diameter to one-tenth of the free diameter of the diaphragm would result in an over-all sound reduction of 8,000:1. It is pointed out that as the damping surface 14 is made wider the degree of damping is increased. By changes in dimension of bore diameter 10 and of the width of surface 14 means are provided for the design of a protective device having a desired transition point and degree of sound reduction.
The selection of material for the supporting structure, 5, deserves attention. It must be conformable because the meatus surfaces of no two auditory canals are alike in either size or shape. It must be soft so as not to cause pressure points. The surface must not be so smooth as to be slippery nor as to cause sweating or wax formation in the canal. It must be sound absorbant so as not to pass sound around the device and thus defeat its purpose. A closed cell polyvinyl elastomer possesses all of these qualities and in addition it has the necessary elasticity to provide for a very simple means of assembly. This latter is of significance in that it makes replacement of this part by the wearer practical when desired. Closed cell polyethylene is somewhat less elastic but has the quality of high conformability and gives a high degree of comfort.
It has been found advantageous to cut the parts for the support structure 15, from cut sheets of the elastomeric material. They are made as round discs with a central perforation. Two are preferred, not cemented surface to surface, as this has been found to produce a much more conformable assembly than when either thicker or cemented material is used and is far superior to molded material which carries a skin surface. When in the ear the direct transmission of sound due to motion of the device in its cushion is negligible except when walking when each step is audible. Normal sounds do not drive the device as a whole since its mass is more than 20,000 times the mass of the diaphragm.
Plastic material is the material of choice for the diaphragm, again for several reasons. First in importance is its low elastic modulus, less than 600,000 p.s.i., as compared with 10,000,000 for Aluminum, for example, since it is desirable to have a diaphragm with as large a central excursion as possible where the diameter is strictly limited by the wearing requirement. Second, its low density is advantageous in keeping the mass to a minimum, important in getting a sensitive diaphragm with good frequency response. The stability of the material under various conditions is a further advantage. Another advantage in plastic material is the wide selection of hardness which enable the selection of various sound response characteristics where desired. Finally, the permeability of these materials to water vapor and gasses is not to be found in metal foils. Having the diaphragm of permeable material aids in avoiding moisture buildup within the ear canal.
To give dimension to this device it has been found that various diaphragm materials of from 0.001 inch to 0.0015 inch in thickness function without distortion of sound of low level. Each performed satisfactorily against high level sound and impace noises with a clearance of about 0.001 inch between the free diaphragm and the surface 14.
From the foregoing description it will be seen that a device formed in accordance with the above teachings is simple in construction and relatively economical to manufacture. It is apparent that all of the objects and advantages of the invention have been accomplished. It will also be apparent, however, that changes may be made in the details of construction and arrangement of parts shown and described without departing from the spirit of the invention as expressed in the accompanying claims. Therefore, it is to be understood that all matter set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.