US3637040A - Ear defenders - Google Patents
Ear defenders Download PDFInfo
- Publication number
- US3637040A US3637040A US843405A US3637040DA US3637040A US 3637040 A US3637040 A US 3637040A US 843405 A US843405 A US 843405A US 3637040D A US3637040D A US 3637040DA US 3637040 A US3637040 A US 3637040A
- Authority
- US
- United States
- Prior art keywords
- shell
- air
- volume
- acoustic
- passage means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000000463 material Substances 0.000 claims description 15
- 230000005540 biological transmission Effects 0.000 claims description 9
- 238000007789 sealing Methods 0.000 claims description 8
- 239000002360 explosive Substances 0.000 claims description 7
- 230000002745 absorbent Effects 0.000 claims description 5
- 239000002250 absorbent Substances 0.000 claims description 5
- 238000004891 communication Methods 0.000 claims description 5
- 230000002093 peripheral effect Effects 0.000 claims description 2
- 230000004044 response Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 4
- 239000004698 Polyethylene Substances 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- -1 polyethylene Polymers 0.000 description 3
- 229920000573 polyethylene Polymers 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 210000005069 ears Anatomy 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 241001125929 Trisopterus luscus Species 0.000 description 1
- 230000005534 acoustic noise Effects 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 210000004907 gland Anatomy 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002984 plastic foam Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000005871 repellent Substances 0.000 description 1
- 239000012858 resilient material Substances 0.000 description 1
Images
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F11/00—Methods or devices for treatment of the ears or hearing sense; Non-electric hearing aids; Methods or devices for enabling ear patients to achieve auditory perception through physiological senses other than hearing sense; Protective devices for the ears, carried on the body or in the hand
- A61F11/06—Protective devices for the ears
- A61F11/14—Protective devices for the ears external, e.g. earcaps or earmuffs
Definitions
- FIG 9 FREQUENCY H /4 7 A 1 ml/f/ C2 M7 1 M2 2 0 C, B P 3 0 H Q OUT FIG /5 FRE UENCY 'INVENTOR ATTORNEY EAR DEFENDERS This invention relates to ear defenders.
- Ear defender assemblies are frequently an integral part of other head-wom equipment such as protective helmets, and in such cases it is difficult to remove the headgear for the occasions on which the wearer wishes to hear normal airborne sounds.
- This difficulty has been reduced by arranging a port or ports suitably disposed in the material of the ear defender shell so arranged that the port or ports can be opened or closed at will.
- the ear defender assembly provides maximum attenuation to airborne sounds andnoises, but when the ports are opened airborne sounds are permitted to reach the wearers ears in a fairly normal manner.
- an ear defender including a shell of rigid material for enclosing a volume of air around a wearers car, a passage in said shell for sound waves to said volume of air, at least one element providing acoustic impedance between the outside of said ear defender and said passage, said impedance being selected in conjunction with the acoustic impedance of said volume of air so as to constitute therewith an acoustic filter which attenuates at least higher frequency components of sound passing to said wearers ear.
- FIG. 1 shows a cross-sectional elevation of an embodiment of an ear defender according to the invention
- FIG. 2 is an end view of said ear defender
- FIG. 3 is the equivalent electrical circuit to the acoustic circuit of said ear defender
- FIG. 4 is a frequency response curve for said ear defender
- FIG. 5 is a cross-sectional elevation of an ear defender in accordance with another embodiment of the invention.
- FIGS. 6 to 10 are electrical equivalent circuits illustrative of the operation of the invention.
- FIGS. 11 to 15 are graphs representing the characteristics of the respective electrical equivalent circuits of FIGS. 6 to 10.
- the member I is a shell of rigid and dense material which can enclose a volume of air around the wearers car (not shown).
- Member 2 is a sealing annulus whose function is the sealing of the forward annular face of the shell to the side of the wearers head and the elimination of acoustic leaks between the internal volume of the shell and the outside air.
- Said member 2 consists preferably of a liquid-filled tube, but alternatively it may be filled with some resilient material such as plastic foam.
- the shell 2 provides a significant degree of attenuation of sound in accordance with known principles.
- ports 3 are provided, and bearing against the outside face of the rear of the shell 1 is a disc member 4 which possesses ports 5 disposed so as to align with the ports 3 when said disc 4 has a suitably relative disposition with the rear face of the shell 1.
- Said disc 4 is arranged o be rotatable by means of the axial mounting 6 and thus if the disc 4 is suitably rotated the holes 3 and 5 areno longer in alignment.
- the disc 4 is covered on its outer face by a disc or pad 7 of suitably porous material such as felt or preferably foamed plastic.
- Disc 7 which is of suitably chosen material and dimensions constitutes an acoustic resistance. Its purpose is to absorb the acoustic energy in any turbulence which is created when the assembly is present in the path of moving air, for example in windy conditions, and reduce the acoustic noise which would otherwise be produced by such turbulence and which would reach the wearer's ear.
- the acoustic resistance which is directly in the path of sound waves passing from the outer air into the volume, 20, enclosed by member I and the ear of the wearer constitutes one element of a lowpass filter of the resistance-capacitance type.
- the capacitive element of said low-pass filter is formed by said air volume 20.
- Said filter is illustrated in FIG. 3 wherein P represents the input pressure of the system and P represents the output pressure.
- the frequency response of this filter is illustrated in FIG. 4.
- the precise value of the effective acoustic resistance in the path of incident sound waves is defined not only by a careful choice of material and dimensions of the disc 7 but also by the size and number of the ports 3 and 5.
- the acoustic impedance of such a plastic disc can be made suitably small compared with the other acoustic impedances in the system.
- An outer housing 9 serves the functions of maintaining in close proximity the relevant elements, and of providing a suitable grip for the required rotation of the acoustic valve assembly.
- a spring member 10 is provided and is arranged to ensure that when the acoustic valve is in the closed position member 4 and the rear face of member 1 are maintained in intimate contact so as to avoid the inlet of sound via any unintentional gap between said member 4 and the rear face of said member 1.
- a telephone receiver 11 is incorporated in the assembly for the reception of speech or other signals via an electrical communications system.
- the telephone receiver is so mounted that it does not obstruct the sound path from the outside air to the wearers car when the acoustic valve arrangement is in the open position.
- a suitable quantity of acoustic absorbent material 12 is incorporated into the volume enclosed by member 1 so as to reduce or effectively eliminate any unwanted acoustic resonances within the volume.
- FIG. 5 parts similar to those shown in FIG. 1 have the same reference numeral.
- the construction is similar to that described above with regard to the shell 1, sealing annulus 2, ports 3, disc member 4 and ports 5.
- Member 15 is an operating means for rotating disc 4, but other means such as, for example, an axially mounted knob, may also be used.
- the enclosed volume 20 shown in FIG. 1 is represented by a shunt capacitance C by classical analogy.
- P represents the input pressure of the system and P represents the output pressure. It can be shown that such a system has zero attenuation provided that the source impedance associated with the energy input is small compared with the impedance of the element C and this is the case when we are concerned with the propagation of sound in free air.
- the response of such a system is shown in FIG. 11.
- this system will provide an attenuation independent of frequency and of degree dependent upon the relative impedances of C and C according to known principles.
- the response of such a system is shown in FIG. 12, and in this embodiment the impedance C is realized by the stiffness of the diaphragm 14 shown in FIG. 5. 7
- the response of the system will be of the form shown in FIG. 13 in which the peak of response occurs at a frequency determined by the impedance of M in conjunction with the combined impedances of C and C It will be appreciated that over a small band of frequencies the attenuation is now zero or may be even less than zero.
- FIG. 9 an element R, associated with diaphragm 14, but not necessarily so, has been added in order to eliminate the undesirable enhancement of the response of the system shown in FIG. 8.
- the response of the system shown in FIG. 9 is as shown in FIG. 14. It can be seen that we now have an approach to a band-pass filter. It will nonnally be the case that when the resilience of diaphragm 14 of FIG. has been suitably chose so as to provide the required degree of low-frequency attenuation, and when the mass M, of diaphragm 14 shown in FIG. 5 has been chosen to provide reduction of this attenuation at the chosen frequency, then the higher frequency cutoff of the system will be undesirably low.
- the frequency range over which there is substantially no attenuation can be suitably chosen to include the range of frequencies which are most important with respect to the intelligible reception of speech, for instance from LOGO-3,000 Hz.
- the fact that at both lower and higher frequencies there is significant attenuation results in a desirable improvement in signal/noise ratio and intelligibility when the wearer of the ear defender assembly is wishing to listen to speech whilst in a noisy situation.
- the curve B in FIG. 15 shows the response of the system when the impedance of element C has been increased due to increased air pressures in the environment surrounding the ear defender assembly. It can be seen from a comparison of curves A and B that significant additional attenuation is introduced over a useful frequency range with consequent improved protection of the wearers ears against the explosive loud noises which produce such an increased air pressure.
- Member 14 is preferably but not necessarily made of a suitable plastics material. It also serves the useful purpose of sealing the acoustic valve assembly against the ingress of moisture and of preventing discomfort to the wearer when the ear defender assembly is used in windy situations.
- the system reverts to a lowpass filter with characteristics similar to those of the embodiment described with respect to FIG. 1.
- the diaphragm is forced into a taut condition by increased air pressure due to explosive noises the attenuation is even greater because there was little initial attenuation of the low frequencies.
- the member 8 is a sheet of polyethylene mounted in a nontaut manner.
- the complete ear defender assembly may be simply supported on the head by means of a headband or it may be incorporated into a protective helmet such as worn by aircrews and the crews of fighting vehicles.
- Ear defender apparatus for protecting the ear of a user against undesirable sound, comprising a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air;
- an acoustic impedance element (7, 14) connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the users ear;
- acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
- acoustic impedance element comprises a diaphragm (14) connected in spaced relation with said shell to define a second volume of air (13) on the opposite side of said passage means from said first volume of air.
- valve-operating means connected at one end with said disc, said valve-operating means (15) extending through said second volume of air and through an opening contained in said diaphragm.
- Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air; and
- an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the user's ear, said acoustic impedance element comprising 1. a resilient diaphragm (14) having properties of stiffness and mass, and
- Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air; b. an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said acoustic impedance element including 1. a resilient diaphragm (14) having properties of stiffness and mass, and
- acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biomedical Technology (AREA)
- Acoustics & Sound (AREA)
- Biophysics (AREA)
- Otolaryngology (AREA)
- Psychology (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Heart & Thoracic Surgery (AREA)
- Vascular Medicine (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Headphones And Earphones (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
Abstract
An ear defender in which acoustic elements are added which in conjunction with the shunt capacitance provided by the volume enclosed by the shell thereof and the wearer''s head constitute a low-pass or band-pass filter.
Description
United States Patent 1151 3,637,040 German 5] Jan. 25, 1972 EAR DEFENDERS [561 References Cited [72] inventor: Anthony Graham Gorman, Ruislip, En- UMTED STATES PATENTS gland 2,390,794 12/1945 Knight ..l79/l 2,672,864 3/1954 Makara.. 128/152 73 Assisnee: A fi Li it d 2,754,365 7/1956 Walters 179/107 2,976,948 3/1961 Thiessen et al. .....181/33 [22] Filed: July 22 1969 125,339 4/1872 Sedgwik ..2/2o9 3,220,505 11/1965 Hargrave ..l81/23 3,335,720 8/1967 A1160 ..128/152 [21] Appl. No.: 843,405
FOREIGN PATENTS OR APPLICATIONS 7 242,047 4/1946 Switzerland 1 28/1 51 [30] Foreign Application Priority Data Aug. 1, 1968 Great Britain ..36,842/68 P June 4, 1969 Great Britain ..28,3 39/69 Laubsche' and Laubsche slxbey [57] ABSTRACT [52] U.S.Cl. ..l8l/33 R, 181/23, 179/182R 511 1111. c1. ..G10k 11 04, H041 1/10 defender Whlch elements are added Whlch [58] Field of Search ..181/33,23; [79/182 156- with the shunt capacitance Pmvided by the volume enclosed by the shell thereof and the wearer's head constitute a low-pass or band-pass filter.
10 Claims, 15 Drawing Figures PATENIEnJuzsmz ,537, sum 1 or 2 FREQUENCY ATTORNEY PAIENIEuJNzsm 3.651040 SHEET 2 0F 2 1' v /N POUT FIG. 6. 0 FREQUENCY C2 7 II I Cf /N I QUr FIG. Z 0 FREQUENCY H6. /2
C2 0-4 7 M1 C /N I 7 our I FIG. 8. 0 FREQUENCY F/c. l1
1 Y A 12 4 1 I P a 7 PIN C] FIG 9 0 FREQUENCY H /4 7 A 1 ml/f/ C2 M7 1 M2 2 0 C, B P 3 0 H Q OUT FIG /5 FRE UENCY 'INVENTOR ATTORNEY EAR DEFENDERS This invention relates to ear defenders.
Ear defender assemblies are frequently an integral part of other head-wom equipment such as protective helmets, and in such cases it is difficult to remove the headgear for the occasions on which the wearer wishes to hear normal airborne sounds. This difficulty has been reduced by arranging a port or ports suitably disposed in the material of the ear defender shell so arranged that the port or ports can be opened or closed at will. When the ports are closed the ear defender assembly provides maximum attenuation to airborne sounds andnoises, but when the ports are opened airborne sounds are permitted to reach the wearers ears in a fairly normal manner.
Such arrangements are liable to suffer from the disadvantages that spurious noises can be generated by the movement of air over the sound inlet arrangements, as for instance occurs in windy conditions, and furthermore frequency distortion is liable to be introduced into the original airborne sound. It is accordingly an object of the present invention to provide an improved ear defender in which one or more of the aforementioned disadvantages are reduced or overcome.
According to the invention there is provided an ear defender including a shell of rigid material for enclosing a volume of air around a wearers car, a passage in said shell for sound waves to said volume of air, at least one element providing acoustic impedance between the outside of said ear defender and said passage, said impedance being selected in conjunction with the acoustic impedance of said volume of air so as to constitute therewith an acoustic filter which attenuates at least higher frequency components of sound passing to said wearers ear.
In order that the invention may'be clearly understood and readily carried into effect it will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 shows a cross-sectional elevation of an embodiment of an ear defender according to the invention;
FIG. 2 is an end view of said ear defender;
FIG. 3 is the equivalent electrical circuit to the acoustic circuit of said ear defender;
FIG. 4 is a frequency response curve for said ear defender;
FIG. 5 is a cross-sectional elevation of an ear defender in accordance with another embodiment of the invention;
FIGS. 6 to 10 are electrical equivalent circuits illustrative of the operation of the invention; and
FIGS. 11 to 15 are graphs representing the characteristics of the respective electrical equivalent circuits of FIGS. 6 to 10.
Referring to FIG. 1, the member I is a shell of rigid and dense material which can enclose a volume of air around the wearers car (not shown). Member 2 is a sealing annulus whose function is the sealing of the forward annular face of the shell to the side of the wearers head and the elimination of acoustic leaks between the internal volume of the shell and the outside air. Said member 2 consists preferably of a liquid-filled tube, but alternatively it may be filled with some resilient material such as plastic foam. In conjunction with member 1 the shell 2 provides a significant degree of attenuation of sound in accordance with known principles.
In the rear face of member 1 ports 3 are provided, and bearing against the outside face of the rear of the shell 1 is a disc member 4 which possesses ports 5 disposed so as to align with the ports 3 when said disc 4 has a suitably relative disposition with the rear face of the shell 1. Said disc 4 is arranged o be rotatable by means of the axial mounting 6 and thus if the disc 4 is suitably rotated the holes 3 and 5 areno longer in alignment. The disc 4 is covered on its outer face by a disc or pad 7 of suitably porous material such as felt or preferably foamed plastic.
In operation when the member 4 is rotated so as to be suitably positioned relative to the rear face of member 1 then the ports 3 and 5 are not in alignment, and so there is no airway from the outside air into the internal volume enclosed by member 1. Under these conditions the full noise and sound attenuation'of the ear defender assembly is achieved.
When the'member 4 is rotated so as to bring ports 3 and 5 into alignment then an airway exists from the outside air into the volume enclosed by member I through the disc 7 and ports 3 and 5. Disc 7 which is of suitably chosen material and dimensions constitutes an acoustic resistance. Its purpose is to absorb the acoustic energy in any turbulence which is created when the assembly is present in the path of moving air, for example in windy conditions, and reduce the acoustic noise which would otherwise be produced by such turbulence and which would reach the wearer's ear. Furthermore the acoustic resistance, which is directly in the path of sound waves passing from the outer air into the volume, 20, enclosed by member I and the ear of the wearer constitutes one element of a lowpass filter of the resistance-capacitance type. The capacitive element of said low-pass filter is formed by said air volume 20. Said filter is illustrated in FIG. 3 wherein P represents the input pressure of the system and P represents the output pressure. The frequency response of this filter is illustrated in FIG. 4. The precise value of the effective acoustic resistance in the path of incident sound waves is defined not only by a careful choice of material and dimensions of the disc 7 but also by the size and number of the ports 3 and 5. According to the well-known considerations which apply to the performance of resistance-capacitance type low-pass filters it is possible to define the effective acoustic resistance of disc 7 to incident sound waves such that transmission of such sounds to the wearers ear is substantially unattenuated up to a chosen frequency f,. Above this frequency the transmission will fall eventually at the rate of 6 db. per octave. If the frequency f is suitably chosen to equal the maximum frequency at which speech sound must be passed substantially unattenuated, for example 3,000 Hz., the arrangement brings about a great improvement in the intelligibility of speech reception under noisy conditions by substantially eliminating all sounds and noises which are not within the frequency range which is necessary for the transmission of intelligible speech.
The disc 7, because of its nature, may require protection by a protective member 8 which consists of a fine mesh grill. If it is necessary to exclude moisture such as may be encountered in conditions of rain then member 8 may consist of a thin disc of suitably flexible moisture-repellent material such as polyethylene. The acoustic impedance of such a plastic disc can be made suitably small compared with the other acoustic impedances in the system. An outer housing 9 serves the functions of maintaining in close proximity the relevant elements, and of providing a suitable grip for the required rotation of the acoustic valve assembly. A spring member 10 is provided and is arranged to ensure that when the acoustic valve is in the closed position member 4 and the rear face of member 1 are maintained in intimate contact so as to avoid the inlet of sound via any unintentional gap between said member 4 and the rear face of said member 1.
A telephone receiver 11 is incorporated in the assembly for the reception of speech or other signals via an electrical communications system. The telephone receiver is so mounted that it does not obstruct the sound path from the outside air to the wearers car when the acoustic valve arrangement is in the open position.
A suitable quantity of acoustic absorbent material 12 is incorporated into the volume enclosed by member 1 so as to reduce or effectively eliminate any unwanted acoustic resonances within the volume.
Referring to FIG. 5, parts similar to those shown in FIG. 1 have the same reference numeral. In this embodiment of the invention the construction is similar to that described above with regard to the shell 1, sealing annulus 2, ports 3, disc member 4 and ports 5.
However, it differs from that described above in that there is added an element of volume '13 and a member 14 which is a thin resilient diaphragm having the mechanical properties of stiffness and mass. Member 15 is an operating means for rotating disc 4, but other means such as, for example, an axially mounted knob, may also be used.
The manner of operation of this embodiment will be described by considering the effects of the individual acoustic elements as they are incorporated into the system in turn.
Referring to FIG. 6, the enclosed volume 20 shown in FIG. 1 is represented by a shunt capacitance C by classical analogy. As before, P represents the input pressure of the system and P represents the output pressure. It can be shown that such a system has zero attenuation provided that the source impedance associated with the energy input is small compared with the impedance of the element C and this is the case when we are concerned with the propagation of sound in free air. The response of such a system is shown in FIG. 11.
Referring to FIG. 7 if we add an impedance C then this system will provide an attenuation independent of frequency and of degree dependent upon the relative impedances of C and C according to known principles. The response of such a system is shown in FIG. 12, and in this embodiment the impedance C is realized by the stiffness of the diaphragm 14 shown in FIG. 5. 7
Referring now to FIG. 8, if the element of mass M of the diaphragm 14 is added, then the response of the system will be of the form shown in FIG. 13 in which the peak of response occurs at a frequency determined by the impedance of M in conjunction with the combined impedances of C and C It will be appreciated that over a small band of frequencies the attenuation is now zero or may be even less than zero.
Referring now to FIG. 9, an element R, associated with diaphragm 14, but not necessarily so, has been added in order to eliminate the undesirable enhancement of the response of the system shown in FIG. 8. The response of the system shown in FIG. 9 is as shown in FIG. 14. It can be seen that we now have an approach to a band-pass filter. It will nonnally be the case that when the resilience of diaphragm 14 of FIG. has been suitably chose so as to provide the required degree of low-frequency attenuation, and when the mass M, of diaphragm 14 shown in FIG. 5 has been chosen to provide reduction of this attenuation at the chosen frequency, then the higher frequency cutoff of the system will be undesirably low.
Referring to FIG. 10, three additional elements namely C representing volume 13 in FIG. 5, M representing the acoustic inertance of the ports 3 and 5 in FIG. 5, and R representing the acoustic resistance of member 12 of FIG. 5 have been added. Member 12 also damps resonances in the cavity 20 of FIG. 5. By suitable proportioning of all of the elements now included in the system according to this invention, the higher frequency resistance of the system may be somewhat extended to provide an overall response as shown by curve A in FIG. 15. It will be seen that over a certain band of frequencies the ratio P /P is unity or very nearly so and thus there is substantially no attenuation over this range of frequencies. At lower frequencies, however, a significant attenuation is introduced and at higher frequencies a significant attenuation is also introduced.
The frequency range over which there is substantially no attenuation can be suitably chosen to include the range of frequencies which are most important with respect to the intelligible reception of speech, for instance from LOGO-3,000 Hz. The fact that at both lower and higher frequencies there is significant attenuation results in a desirable improvement in signal/noise ratio and intelligibility when the wearer of the ear defender assembly is wishing to listen to speech whilst in a noisy situation.
The curve B in FIG. 15 shows the response of the system when the impedance of element C has been increased due to increased air pressures in the environment surrounding the ear defender assembly. It can be seen from a comparison of curves A and B that significant additional attenuation is introduced over a useful frequency range with consequent improved protection of the wearers ears against the explosive loud noises which produce such an increased air pressure.
If the impedance of C is reduced, by making the diaphragm 14 of flexible material such as sheet polyethylene which is mounted in a nontaut manner, so that its impedance is negligibly small with respect to the impedance of the other acoustic elements in the system, the system reverts to a lowpass filter with characteristics similar to those of the embodiment described with respect to FIG. 1. However when the diaphragm is forced into a taut condition by increased air pressure due to explosive noises the attenuation is even greater because there was little initial attenuation of the low frequencies. The same effect can be achieved in a modification of the embodiment shown in FIG. I in which the member 8 is a sheet of polyethylene mounted in a nontaut manner. This has small impedance compared with the other element in the system and therefore effects substantially no attenuation. However in the presence of increased air pressure due to explosive loud noises the sheet is driven taut and then acts as 'a substantial attenuating impedance. In both cases when the member is in its taut condition the attenuation in the ear defender is similar to that when the acoustic valve is closed.
The complete ear defender assembly may be simply supported on the head by means of a headband or it may be incorporated into a protective helmet such as worn by aircrews and the crews of fighting vehicles.
What is claimed is:
1. Ear defender apparatus for protecting the ear of a user against undesirable sound, comprising a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air;
a layer of acoustic absorbent material (12) lining the interior surface of said shell to reduce unwarranted resonance in said volume of air;
an acoustic impedance element (7, 14) connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the users ear; and
acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
2. Apparatus as defined in claim I, and further including spring means (10) biasing said disc in the direction of sealed engagement with said shell.
3. Apparatus as defined in claim I, wherein said acoustic impedance element comprises a diaphragm (14) connected in spaced relation with said shell to define a second volume of air (13) on the opposite side of said passage means from said first volume of air.
4. Apparatus as defined in claim 3, and further including valve-operating means connected at one end with said disc, said valve-operating means (15) extending through said second volume of air and through an opening contained in said diaphragm.
5. Apparatus as defined in claim 1, wherein said acoustic impedance element comprises a porous pad (7).
6. Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air; and
b. an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the user's ear, said acoustic impedance element comprising 1. a resilient diaphragm (14) having properties of stiffness and mass, and
2. means mounting said diaphragm in an initial nontaut condition to enclose a second volume of air (13) in communication with the end of said passage means remote from said first volume of air, said diaphragm being operable to a taut condition by the increased air pressure produced by explosive noises, thereby increasing the attenuation afforded by said acoustic impedance element.
7. Apparatus as defined in claim 6, and further including a sealing annulus of flexible material connected with the peripheral edge portion of said shell for sealing said shell to the wearers head.
8. Apparatus as defined in claim 6, and further including a layer of acoustic absorbent material lining the interior surface of said shell to reduce unwanted resonance in said first volume of air.
9. Apparatus as defined in claim 6, and further including acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
l0. Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the users ear, said shell containing passage means (3) for conducting sound waves to said volume of air; b. an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said acoustic impedance element including 1. a resilient diaphragm (14) having properties of stiffness and mass, and
2. means mounting said diaphragm in an initial nontaut condition to enclose a second volume of air (13) in communication with the end of said passage means remote from said first volume of air, said diaphragm being operable to a taut condition by the increased air pressure produced by explosive noises, thereby increasing the attenuation afforded by said acoustic impedance element; and
c. acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
Claims (12)
1. Ear defender apparatus for protecting the ear of a user against undesirable sound, comprising a shell (1) adapted to enclose a first volume of air (20) about the user''s ear, said shell containing passage means (3) for conducting sound waves to said volume of air; a layer of acoustic absorbent material (12) lining the interior surface of said shell to reduce unwarranted resonance in said volume of air; an acoustic impedance element (7, 14) connected with the exteRnal surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the user''s ear; and acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
2. Apparatus as defined in claim 1, and further including spring means (10) biasing said disc in the direction of sealed engagement with said shell.
2. means mounting said diaphragm in an initial nontaut condition to enclose a second volume of air (13) in communication with the end of said passage means remote from said first volume of air, said diaphragm being operable to a taut condition by the increased air pressure produced by explosive noises, thereby increasing the attenuation afforded by said acoustic impedance element.
2. means mounting said diaphragm in an initial nontaut condition to enclose a second volume of air (13) in communication with the end of said passage means remote from said first volume of air, said diaphragm being operable to a taut condition by the increased air pressure produced by explosive noises, thereby increasing the attenuation afforded by said acoustic impedance element; and c. acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
3. Apparatus as defined in claim 1, wherein said acoustic impedance element comprises a diaphragm (14) connected in spaced relation with said shell to define a second volume of air (13) on the opposite side of said passage means from said first volume of air.
4. Apparatus as defined in claim 3, and further including valve-operating means connected at one end with said disc, said valve-operating means (15) extending through said second volume of air and through an opening contained in said diaphragm.
5. Apparatus as defined in claim 1, wherein said acoustic impedance element comprises a porous pad (7).
6. Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the user''s ear, said shell containing passage means (3) for conducting sound waves to said volume of air; and b. an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmission of sound to said volume of air through said passage means, said impedance element cooperating with said first volume of air to define an acoustic filter that attenuates at least the higher frequency components of sound that would otherwise pass to the user''s ear, said acoustic impedance element comprising
7. Apparatus as defined in claim 6, and further including a sealing annulus of flexible material connected with the peripheral edge portion of said shell for sealing said shell to the wearer''s head.
8. Apparatus as defined in claim 6, and further including a layer of acoustic absorbent material lining the interior surface of said shell to reduce unwanted resonance in said first volume of air.
9. Apparatus as defined in claim 6, and further including acoustic valve means (4) arranged between said shell and said impedance element for operation between open and closed positions relative to said passage means, said acoustic valve means including a disc (4) connected for coplanar movement relative to said shell, said disc containing at least one aperture (5) arranged for selective alignment with the orifice of said passage means.
10. Ear defender means for protecting the ear of a user against undesirable sound, comprising a. a shell (1) adapted to enclose a first volume of air (20) about the user''s ear, said shell containing passage means (3) for conducting sound waves to said volume of air; b. an acoustic impedance element connected with the external surface of said shell across the orifice of said passage means for controlling the transmiSsion of sound to said volume of air through said passage means, said acoustic impedance element including
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB3684268 | 1968-08-01 | ||
GB2833969A GB1276498A (en) | 1968-08-01 | 1968-08-01 | Improvements in and relating to ear defenders |
Publications (1)
Publication Number | Publication Date |
---|---|
US3637040A true US3637040A (en) | 1972-01-25 |
Family
ID=26259333
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US843405A Expired - Lifetime US3637040A (en) | 1968-08-01 | 1969-07-22 | Ear defenders |
Country Status (6)
Country | Link |
---|---|
US (1) | US3637040A (en) |
CH (1) | CH496441A (en) |
DE (1) | DE1938259C3 (en) |
FR (1) | FR2014846A1 (en) |
NL (1) | NL156042B (en) |
SE (1) | SE352526B (en) |
Cited By (25)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3837681A (en) * | 1973-06-28 | 1974-09-24 | W Reynolds | Stethoscope |
US3934100A (en) * | 1974-04-22 | 1976-01-20 | Seeburg Corporation | Acoustic coupler for use with auditory equipment |
US3938616A (en) * | 1973-11-27 | 1976-02-17 | Brownfield Swayze W | Sound multiplier |
EP0091829A1 (en) * | 1982-04-13 | 1983-10-19 | The Marconi Company Limited | Ear defenders |
EP0092362A2 (en) * | 1982-04-19 | 1983-10-26 | Clayton H. Allen | Nonlinear passive acoustic filtering |
US4459707A (en) * | 1982-08-23 | 1984-07-17 | Cabot Corporation | Ear protecting device |
US4465159A (en) * | 1983-03-11 | 1984-08-14 | Cabot Corporation | Nonlinear ear protecting device |
WO2002080830A1 (en) * | 2001-04-09 | 2002-10-17 | Cabot Safety Intermediate Corporation | Earmuff with controlled leak |
US20030095670A1 (en) * | 2000-07-25 | 2003-05-22 | Wurtz Michael Jon | Active-noise-reduction headsets with front-cavity venting |
US20040125976A1 (en) * | 2002-12-30 | 2004-07-01 | Reneker Brian Scott | Headphones or earmuffs with a user operated mechanical device that controls the volume of exterior sound entering the ear of the user |
US20050008167A1 (en) * | 2003-04-30 | 2005-01-13 | Achim Gleissner | Device for picking up/reproducing audio signals |
US20050283882A1 (en) * | 2004-01-23 | 2005-12-29 | Elliott Berger | High attenuating earmuff device |
US20070253589A1 (en) * | 2006-04-26 | 2007-11-01 | Foo Toon J | Earphone |
US20080123884A1 (en) * | 2006-08-22 | 2008-05-29 | David Donenfeld | Passive hearing aid device |
US20080165981A1 (en) * | 2000-07-25 | 2008-07-10 | Michael Jon Wurtz | Active-noise-reduction headsets with front-cavity venting |
US20090049586A1 (en) * | 2007-08-14 | 2009-02-26 | Head Germany, Gmbh | Safety helmet |
US20110158421A1 (en) * | 2009-12-24 | 2011-06-30 | Voix Jeremie | In-ear device with selectable frequency response |
USD735161S1 (en) * | 2013-08-16 | 2015-07-28 | Microsoft Corporation | Earcups for a headset |
USD735691S1 (en) * | 2013-08-16 | 2015-08-04 | Microsoft Corporation | Earcups for a headset |
USD848396S1 (en) * | 2017-11-02 | 2019-05-14 | Honeywell International Inc. | Noise monitoring headset |
USD864899S1 (en) * | 2018-05-11 | 2019-10-29 | Techcool Industry Development Co., Ltd. | Headset |
USD877714S1 (en) | 2018-09-25 | 2020-03-10 | Microsoft Corporation | Headset |
USD878327S1 (en) | 2018-09-25 | 2020-03-17 | Microsoft Corporation | Earcups for a headset |
US20220168149A1 (en) * | 2019-03-21 | 2022-06-02 | Minuendo As | Ear protection |
US20230021291A1 (en) * | 2019-12-23 | 2023-01-19 | Minuendo As | Hearing protection device |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2546355A1 (en) * | 1983-05-19 | 1984-11-23 | Fame | PROTECTIVE HELMET AND SOUND SIGNAL TRANSMITTER |
DE3623315A1 (en) * | 1986-07-11 | 1988-01-21 | Wolfgang Brede Kg | Device for a low-pass hearing protection |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US125339A (en) * | 1872-04-02 | Improvement in ear-muffs | ||
US2390794A (en) * | 1944-02-21 | 1945-12-11 | Zenith Radio Corp | Frequency response control |
CH242047A (en) * | 1944-05-20 | 1946-04-15 | Luzius Prof Dr Med Rueedi | Device for the protection of the hearing against harmful sound effects. |
US2672864A (en) * | 1951-07-18 | 1954-03-23 | Makara Frank | Audio mask |
US2754365A (en) * | 1952-09-15 | 1956-07-10 | Maico Company Inc | Acoustical tone control for wearable hearing aids |
US2976948A (en) * | 1958-01-03 | 1961-03-28 | Canada Nat Res Council | Mechanical device for distance discrimination of sounds |
US3220505A (en) * | 1964-04-01 | 1965-11-30 | Willard B Hargrave | Audiometric headset |
US3335720A (en) * | 1965-06-02 | 1967-08-15 | Leonard Peter Frieder | Valve for sound attenuating device |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL78163C (en) * | 1950-05-11 | |||
FR1145964A (en) * | 1954-05-20 | 1957-11-05 | Ca Nat Research Council | Eardrums |
GB1183232A (en) * | 1966-02-25 | 1970-03-04 | Kahn Leonard R | Improvements in or relating to Hearing Protection Systems |
-
1969
- 1969-07-22 US US843405A patent/US3637040A/en not_active Expired - Lifetime
- 1969-07-25 NL NL6911432.A patent/NL156042B/en unknown
- 1969-07-28 DE DE1938259A patent/DE1938259C3/en not_active Expired
- 1969-07-28 FR FR6925681A patent/FR2014846A1/fr not_active Withdrawn
- 1969-07-31 SE SE10763/69*A patent/SE352526B/xx unknown
- 1969-08-01 CH CH1180569A patent/CH496441A/en not_active IP Right Cessation
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US125339A (en) * | 1872-04-02 | Improvement in ear-muffs | ||
US2390794A (en) * | 1944-02-21 | 1945-12-11 | Zenith Radio Corp | Frequency response control |
CH242047A (en) * | 1944-05-20 | 1946-04-15 | Luzius Prof Dr Med Rueedi | Device for the protection of the hearing against harmful sound effects. |
US2672864A (en) * | 1951-07-18 | 1954-03-23 | Makara Frank | Audio mask |
US2754365A (en) * | 1952-09-15 | 1956-07-10 | Maico Company Inc | Acoustical tone control for wearable hearing aids |
US2976948A (en) * | 1958-01-03 | 1961-03-28 | Canada Nat Res Council | Mechanical device for distance discrimination of sounds |
US3220505A (en) * | 1964-04-01 | 1965-11-30 | Willard B Hargrave | Audiometric headset |
US3335720A (en) * | 1965-06-02 | 1967-08-15 | Leonard Peter Frieder | Valve for sound attenuating device |
Cited By (29)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3837681A (en) * | 1973-06-28 | 1974-09-24 | W Reynolds | Stethoscope |
US3938616A (en) * | 1973-11-27 | 1976-02-17 | Brownfield Swayze W | Sound multiplier |
US3934100A (en) * | 1974-04-22 | 1976-01-20 | Seeburg Corporation | Acoustic coupler for use with auditory equipment |
EP0091829A1 (en) * | 1982-04-13 | 1983-10-19 | The Marconi Company Limited | Ear defenders |
EP0092362A2 (en) * | 1982-04-19 | 1983-10-26 | Clayton H. Allen | Nonlinear passive acoustic filtering |
EP0092362A3 (en) * | 1982-04-19 | 1985-11-21 | Clayton H. Allen | Nonlinear passive acoustic filtering |
US4459707A (en) * | 1982-08-23 | 1984-07-17 | Cabot Corporation | Ear protecting device |
US4465159A (en) * | 1983-03-11 | 1984-08-14 | Cabot Corporation | Nonlinear ear protecting device |
US20080165981A1 (en) * | 2000-07-25 | 2008-07-10 | Michael Jon Wurtz | Active-noise-reduction headsets with front-cavity venting |
US20030095670A1 (en) * | 2000-07-25 | 2003-05-22 | Wurtz Michael Jon | Active-noise-reduction headsets with front-cavity venting |
US7317802B2 (en) * | 2000-07-25 | 2008-01-08 | Lightspeed Aviation, Inc. | Active-noise-reduction headsets with front-cavity venting |
WO2002080830A1 (en) * | 2001-04-09 | 2002-10-17 | Cabot Safety Intermediate Corporation | Earmuff with controlled leak |
US6826287B2 (en) | 2001-04-09 | 2004-11-30 | Cabot Safety Intermediate Corporation | Earmuff with controlled leak |
US20040125976A1 (en) * | 2002-12-30 | 2004-07-01 | Reneker Brian Scott | Headphones or earmuffs with a user operated mechanical device that controls the volume of exterior sound entering the ear of the user |
US20050008167A1 (en) * | 2003-04-30 | 2005-01-13 | Achim Gleissner | Device for picking up/reproducing audio signals |
US20050283882A1 (en) * | 2004-01-23 | 2005-12-29 | Elliott Berger | High attenuating earmuff device |
US20070253589A1 (en) * | 2006-04-26 | 2007-11-01 | Foo Toon J | Earphone |
US20080123884A1 (en) * | 2006-08-22 | 2008-05-29 | David Donenfeld | Passive hearing aid device |
US20090049586A1 (en) * | 2007-08-14 | 2009-02-26 | Head Germany, Gmbh | Safety helmet |
US20110158421A1 (en) * | 2009-12-24 | 2011-06-30 | Voix Jeremie | In-ear device with selectable frequency response |
US8903114B2 (en) | 2009-12-24 | 2014-12-02 | Sonomax Technologies Inc. | In-ear device with selectable frequency response |
USD735161S1 (en) * | 2013-08-16 | 2015-07-28 | Microsoft Corporation | Earcups for a headset |
USD735691S1 (en) * | 2013-08-16 | 2015-08-04 | Microsoft Corporation | Earcups for a headset |
USD848396S1 (en) * | 2017-11-02 | 2019-05-14 | Honeywell International Inc. | Noise monitoring headset |
USD864899S1 (en) * | 2018-05-11 | 2019-10-29 | Techcool Industry Development Co., Ltd. | Headset |
USD877714S1 (en) | 2018-09-25 | 2020-03-10 | Microsoft Corporation | Headset |
USD878327S1 (en) | 2018-09-25 | 2020-03-17 | Microsoft Corporation | Earcups for a headset |
US20220168149A1 (en) * | 2019-03-21 | 2022-06-02 | Minuendo As | Ear protection |
US20230021291A1 (en) * | 2019-12-23 | 2023-01-19 | Minuendo As | Hearing protection device |
Also Published As
Publication number | Publication date |
---|---|
DE1938259A1 (en) | 1970-02-05 |
DE1938259C3 (en) | 1974-06-06 |
SE352526B (en) | 1973-01-08 |
NL6911432A (en) | 1970-02-03 |
NL156042B (en) | 1978-03-15 |
DE1938259B2 (en) | 1973-11-08 |
FR2014846A1 (en) | 1970-04-24 |
CH496441A (en) | 1970-09-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3637040A (en) | Ear defenders | |
US4833719A (en) | Method and apparatus for attentuating external origin noise reaching the eardrum, and for improving intelligibility of electro-acoustic communications | |
US4441576A (en) | Nonlinear passive acoustic filtering | |
US3798393A (en) | Headphone construction | |
US4570746A (en) | Wind/breath screen for a microphone | |
US6801629B2 (en) | Protective hearing devices with multi-band automatic amplitude control and active noise attenuation | |
US5740258A (en) | Active noise supressors and methods for use in the ear canal | |
US6567525B1 (en) | Supra aural active noise reduction headphones | |
US5524058A (en) | Apparatus for performing noise cancellation in telephonic devices and headwear | |
US3602329A (en) | Conformal ear enclosure | |
US2603724A (en) | Sound translating device arranged to eliminate extraneous sound | |
US5659620A (en) | Ear microphone for insertion in the ear in connection with portable telephone or radios | |
US4979586A (en) | Acoustically shielded motorcycle helmet speaker enclosure | |
JPH0412977B2 (en) | ||
US4924502A (en) | Means for stabilizing sound pressure produced at the eardrum under an earpad | |
KR940005185A (en) | Phone headphones to reduce ambient noise | |
WO2011022370A1 (en) | Feedforward anr device cover | |
JPH04267699A (en) | Ear protective cup for ear cover or headphone | |
GB2188210A (en) | Acoustic noise reduction in ear defenders | |
US6163610A (en) | Telephonic handset apparatus having an earpiece monitor and reduced inter-user variability | |
GB2311187A (en) | Radiotelephone with an air gap provided between the speaker and sound ports | |
US3126977A (en) | Hearing aid apparatus | |
JPH03214892A (en) | Noise reducing device | |
US6771788B1 (en) | Shielded microphone | |
US4139075A (en) | Loudspeaker device |